| 1. |
- Eroukhmanoff, Fabrice, et al.
(author)
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THE ROLE OF DIFFERENT REPRODUCTIVE BARRIERS DURING PHENOTYPIC DIVERGENCE OF ISOPOD ECOTYPES
- 2011
-
In: Evolution. - : Wiley-Blackwell. - 0014-3820 .- 1558-5646. ; 65:9, s. 2631-2640
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Journal article (peer-reviewed)abstract
- The question of how diverging populations become separate species by restraining gene flow is a central issue in evolutionary biology. Assortative mating might emerge early during adaptive divergence, but the role of other types of reproductive barriers such as migration modification have recently received increased attention. We demonstrate that two recently diverged ecotypes of a freshwater isopod (Asellus aquaticus) have rapidly developed premating isolation, and this isolation barrier has emerged independently and in parallel in two south Swedish lakes. This is consistent with ecological speciation theory, which predicts that reproductive isolation arises as a byproduct of ecological divergence. We also find that in one of these lakes, habitat choice acts as the main barrier to gene flow. These observations and experimental results suggest that migration modification might be as important as assortative mating in the early stages of ecological speciation. Simulations suggest that the joint action of these two isolating barriers is likely to greatly facilitate adaptive divergence, compared to if each barrier was acting alone.
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| 2. |
- Holmér, Jennie, et al.
(author)
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The origin of polymorphic crypsis in a heterogeneous environment
- 2010
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In: Evolution. - : Wiley. - 1558-5646 .- 0014-3820. ; 64, s. 1386-1394
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Journal article (peer-reviewed)abstract
- ABSTRACT Polymorphic crypsis has been observed in several taxa, but has, until now, lacked a firm theoretical understanding. How does a single morph, well camouflaged in one type of habitat, evolve crypsis in another, not isolated, habitat? We here analyze a model of one prey species living in two different habitats connected by passive dispersal. We find that the rate of dispersal, the trade-off between crypticity in the habitats, and the amount of predation determines whether the prey species can become cryptic in two different habitats through evolutionary branching. Intermediate values of all parameters seem to promote evolutionary branching leading to polymorphism, and a more extreme value of one parameter can be balanced by another. Other parameter combinations lead to either a single habitat specialist or an intermediate generalist type, partly cryptic in both habitat. When the predator follows a type III functional response the parameter space for when the prey will undergo evolutionary branching is remarkably larger than the corresponding parameter space for a type II functional response. Evolutionary branching can occur both at the intermediate generalist strategy, or close to a specialist strategy.
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| 3. |
- Jenkins, Tania, et al.
(author)
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Migratory behavior of birds affects their coevolutionary relationship with blood parasites
- 2012
-
In: Evolution. - : Wiley. - 1558-5646 .- 0014-3820. ; 66:3, s. 740-751
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Journal article (peer-reviewed)abstract
- Host traits, such as migratory behavior, could facilitate the dispersal of disease-causing parasites, potentially leading to the transfer of infections both across geographic areas and between host species. There is, however, little quantitative information on whether variation in such host attributes does indeed affect the evolutionary outcome of host-parasite associations. Here, we employ Leucocytozoon blood parasites of birds, a group of parasites closely related to avian malaria, to study host-parasite coevolution in relation to host behavior using a phylogenetic comparative approach. We reconstruct the molecular phylogenies of both the hosts and parasites and use cophylogenetic tools to assess whether each host-parasite association contributes significantly to the overall congruence between the two phylogenies. We find evidence for a significant fit between host and parasite phylogenies in this system, but show that this is due only to associations between nonmigrant parasites and their hosts. We also show that migrant bird species harbor a greater genetic diversity of parasites compared with nonmigrant species. Taken together, these results suggest that the migratory habits of birds could influence their coevolutionary relationship with their parasites, and that consideration of host traits is important in predicting the outcome of coevolutionary interactions.
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| 4. |
- Johansson, Jacob
(author)
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Evolutionary responses to environmental changes: How does competition affect adaptation?
- 2008
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In: Evolution. - : Wiley. - 1558-5646 .- 0014-3820. ; 62:2, s. 421-435
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Journal article (peer-reviewed)abstract
- The role and importance of ecological interactions for evolutionary responses to environmental changes is to large extent unknown. Here it is shown that interspecific competition may slow down rates of adaptation substantially and fundamentally change patterns of adaptation to long-term environmental changes. In the model investigated here, species compete for resources distributed along an ecological niche space. Environmental change is represented by a slowly moving resource maximum and evolutionary responses of single species are compared with responses of coalitions of two and three competing species. In scenarios with two and three species, species that are favored by increasing resource availability increase in equilibrium population size whereas disfavored species decline in size. increased competition makes it less favorable for individuals of a disfavored species to occupy a niche close to the maximum and reduces the selection pressure for tracking the moving resource distribution. Individual-based simulations and an analysis using adaptive dynamics show that the combination of weaker selection pressure and reduced population size reduces the evolutionary rate of the disfavored species considerably. If the resource landscape moves stochastically, weak evolutionary responses cause large fluctuations in population size and thereby large extinction risk for competing species, whereas a single species subject to the same environmental variability may track the resource maximum closely and maintain a much more stable population size. Other studies have shown that competitive interactions may amplify changes in mean population sizes due to environmental changes and thereby increase extinction risks. This study accentuates the harmful role of competitive interactions by illustrating that they may also decrease rates of adaptation. The slowdown in evolutionary rates caused by competition may also contribute to explain low rates of morphological change in spite of large environmental fluctuations found in fossil records.
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| 5. |
- Kuchta, Shawn, et al.
(author)
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Why does the Yellow-eyed ensatina have yellow eyes? Batesian mimicry of Pacific newts (genus Taricha) by the salamander Ensatina eschscholtzii xanthoptica
- 2008
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In: Evolution. - : Wiley. - 1558-5646 .- 0014-3820. ; 62:4, s. 984-990
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Journal article (peer-reviewed)abstract
- Color patterns commonly vary geographically within species, but it is rare that such variation corresponds with divergent antipredator strategies. The polymorphic salamander Ensatina eschscholtzii, however, may represent such a case. In this species, most subspecies are cryptically colored, whereas E. e. xanthoptica, the Yellow eyed ensatina, is hypothesized to be an aposematic mimic of highly toxic Pacific newts (genus Taricha). To test the mimicry hypothesis, we conducted feeding trials using Western Scrub-Jays, Aphelocoma californica. In every feeding trial, we found that jays, following presentation with the presumed model (T. torosa), were more hesitant to contact the presumed mimic (E. e. xanthoptica) than a control subspecies lacking the postulated aposematic colors (E. e. oregonensis). The median time to contact was 315 sec for the mimic and 52 sec for the control. These results support the mimicry hypothesis, and we suggest that E. e. xanthoptica is likely a Batesian mimic, rather a Mullerian or quasi-Batesian mimic, of Pacific newts.
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| 6. |
- Lassance, Jean-Marc, et al.
(author)
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Gene genealogies reveal differentiation at sex pheromone olfactory receptor loci in pheromone strains of the European corn borer, Ostrinia nubilalis
- 2011
-
In: Evolution. - : Wiley. - 1558-5646 .- 0014-3820. ; 65:6, s. 1583-1593
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Journal article (peer-reviewed)abstract
- Males of the E and Z strains of the European corn borer Ostrinia nubilalis (Lepidoptera: Crambidae) are attracted to different blends of the same pheromone components. The difference in male behavioral response is controlled by the sex-linked locus Resp. The two types of males have identical neuroanatomy but their physiological specificity is reversed, suggesting that variation at the periphery results in behavioral change. Differences in the olfactory receptors (ORs) could explain the strain-specific antennal response and blend preference. Gene genealogies can provide insights into the processes involved in speciation and allow delineation of genome regions that contribute to reproductive barriers. We used intronic DNA sequences from five OR-encoding genes to investigate whether they exhibit fixed differences between strains and therefore might contribute to reproductive isolation. Although two genealogies revealed shared polymorphism, molecular polymorphism at three genes revealed nearly fixed differences between strains. These three OR genes map to the sex chromosome, but our data indicate that the distance between Resp and the ORs is > 20 cM, making it unlikely that variation in pheromone-sensitive OR genes is directly responsible for the difference in behavioral response. However, differences in male antennal response may have their origin in the selection of strain-specific alleles.
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| 7. |
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| 8. |
- Olsson, Mats, 1960, et al.
(author)
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IN HOT PURSUIT: FLUCTUATING MATING SYSTEM AND SEXUAL SELECTION IN SAND LIZARDS
- 2011
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In: EVOLUTION. - : Wiley. - 0014-3820. ; Online 5 NOV 2010, s. 574-583
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Journal article (peer-reviewed)abstract
- Abstract: A changing climate is expected to have profound effects on many aspects of ectotherm biology. We report on a decade-long study of free-ranging sand lizards (Lacerta agilis), exposed to an increasing mean mating season temperature and with known operational sex ratios. We assessed year-to-year variation in sexual selection on body size and postcopulatory sperm competition and cryptic female choice. Higher temperature was not linked to strength of sexual selection on body mass, but operational sex ratio (more males) did increase the strength of sexual selection on body size. Elevated temperature increased mating rate and number of sires per clutch with positive effects on offspring fitness. In years when the "quality" of a female's partners was more variable (in standard errors of a male sexual ornament), clutches showed less multiple paternity. This agrees with prior laboratory trials in which females exercised stronger cryptic female choice when male quality varied more. An increased number of sires contributing to within-clutch paternity decreased the risk of having malformed offspring. Ultimately, such variation may contribute to highly dynamic and shifting selection mosaics in the wild, with potential implications for the evolutionary ecology of mating systems and population responses to rapidly changing
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| 9. |
- Sanchez Guillen, Rosa, et al.
(author)
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Strong asymmetry in the relative strengths of prezygotic and postzygotic barriers between two damselfly sister species
- 2012
-
In: Evolution. - : Wiley. - 1558-5646 .- 0014-3820. ; 66:3, s. 690-707
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Journal article (peer-reviewed)abstract
- One of the longest debates in biology has been over the relative importance of different isolating barriers in speciation. However, for most species, there are few data evaluating their relative contributions and we can only speculate on the general roles of pre- and postzygotic isolation. Here, we quantify the absolute and cumulative contribution of 19 potential reproductive barriers between two sympatric damselfly sister species, Ischnura elegans and I. graellsii, including both premating (habitat, temporal, sexual and mechanical isolation) and postmating barriers (prezygotic: sperm insemination success and removal rate, oviposition success, fertility, fecundity; postzygotic: hybrid viability, hybrid sterility and hybrid breakdown). In sympatry, total reproductive isolation between I. elegans females and I. graellsii males was 95.2%, owing mostly to a premating mechanical incompatibility (93.4%), whereas other barriers were of little importance. Isolation between I. graellsii females and I. elegans males was also nearly complete (95.8%), which was caused by the cumulative action of multiple prezygotic (n= 4, 75.4%) and postzygotic postmating barriers (n= 5, 7.4%). Our results suggest that premating barriers are key factors in preventing gene flow between species, and that the relative strengths of premating barriers is highly asymmetrical between the reciprocal crosses.
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| 10. |
- Smadja, Carole M, et al.
(author)
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Large-scale candidate gene scan reveals the role of chemoreceptor genes in host plant specialisation and speciation in the pea aphid
- 2012
-
In: Evolution. - : Wiley. - 1558-5646 .- 0014-3820. ; 66:9, s. 2723-2738
-
Journal article (peer-reviewed)abstract
- Understanding the drivers of speciation is critical to interpreting patterns of biodiversity. The identification of the genetic changes underlying adaptation and reproductive isolation is necessary to link barriers to gene flow to the causal origins of divergence. Here, we present a novel approach to the genetics of speciation, which should complement the commonly used approaches of quantitative trait locus mapping and genome-wide scans for selection. We present a large-scale candidate gene approach by means of sequence capture, applied to identifying the genetic changes underlying reproductive isolation in the pea aphid, a model system for the study of ecological speciation. Targeted resequencing enabled us to scale up the candidate gene approach, specifically testing for the role of chemosensory gene families in host plant specialization. Screening for the signature of divergence under selection at 172 candidate and noncandidate loci, we revealed a handful of loci that show high levels of differentiation among host races, which almost all correspond to odorant and gustatory receptor genes. This study offers the first indication that some chemoreceptor genes, often tightly linked together in the genome, could play a key role in local adaptation and reproductive isolation in the pea aphid and potentially other phytophagous insects. Our approach opens a new route toward the functional genomics of ecological speciation.
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| 11. |
- Svensson, Erik, et al.
(author)
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A ROLE FOR LEARNING IN POPULATION DIVERGENCE OF MATE PREFERENCES.
- 2010
-
In: Evolution. - : Wiley. - 1558-5646 .- 0014-3820. ; 64, s. 3101-3113
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Journal article (peer-reviewed)abstract
- ABSTRACT Learning and other forms of phenotypic plasticity have been suggested to enhance population divergence. Mate preferences can develop by learning, and species recognition might not be entirely genetic. We present data on female mate preferences of the banded demoiselle (Calopteryx splendens) that suggest a role for learning in population divergence and species recognition. Populations of this species are either allopatric or sympatric with a phenotypically similar congener (C. virgo). These two species differ mainly in the amount of wing melanisation in males, and wing patches thus mediate sexual isolation. In sympatry, sexually experienced females discriminate against large melanin wing patches in heterospecific males. In contrast, in allopatric populations within the same geographic region, females show positive ("open-ended") preferences for such large wing patches. Virgin C. splendens females do not discriminate against heterospecific males. Moreover, physical exposure experiments of such virgin females to con- or hetero specific males significantly influences their subsequent mate preferences. Species recognition is thus not entirely genetic and it is partly influenced by interactions with mates. Learning causes pronounced population divergence in mate preferences between these weakly genetically differentiated populations, and results in a highly divergent pattern of species recognition at a small geographic scale.
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| 12. |
- Svensson, Erik, et al.
(author)
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Intralocus Sexual Conflict over Immune Defense, Gender Load and Sex-Specific Signaling in a Natural Lizard Population.
- 2009
-
In: Evolution. - : Wiley. - 1558-5646 .- 0014-3820. ; 63:12, s. 3124-3135
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Journal article (peer-reviewed)abstract
- ABSTRACT In species with separate sexes, antagonistic selection on males and females (intralocus sexual conflict) can result in a gender load that can be resolved through the evolution of sexual dimorphism. We present data on intralocus sexual conflict over immune defense in a natural population of free-ranging lizards (Uta stansburiana) and discuss the resolution of this conflict. Intralocus sexual conflict arises from correlational selection between immune defense and orange throat coloration in these lizards. Males with orange throats and high antibody responses had enhanced survival, but the same trait combination reduced female fitness. This sexual antagonism persisted across the life-cycle and was concordant between the juvenile and adult life stages. The opposing selective pressure on males and females is ameliorated by a negative intersexual genetic correlation (rm,f =-0.86) for immune defense. Throat coloration was also genetically correlated with immune defense, but the sign of this genetic correlation differed between the sexes. This resulted in sex-specific signaling of immunological condition. We also found evidence for a sex-specific maternal effect on sons with potential to additionally reduce the gender load. These results have implications for signaling evolution, genetic integration between adaptive traits, sex allocation and mutual mate choice for indirect fitness benefits.
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| 13. |
- Bergek, Sara, 1979-, et al.
(author)
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Cryptic barriers to dispersal within a lake allow genetic differentiation of Eurasian perch
- 2007
-
In: Evolution. - Oxford : Wiley-Blackwell. - 0014-3820 .- 1558-5646. ; 61:8, s. 2035-2041
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Journal article (peer-reviewed)abstract
- Gene flow between coexisting or nearby populations normally prevents genetic divergence and local adaptation. Despite this, there are an increasing number of reports of sympatric sister taxa, indicating potential divergence and speciation in the face of gene flow. A large number of such reported cases involve lake-dwelling fish, which are expected to run into few physical barriers to dispersal within their aquatic habitat. However, such cases may not necessarily reflect sympatric speciation if cryptic dispersal barriers are common in lakes and other aquatic systems. In this study, we examined genetic differentiation in perch (Perca fluviatilis L.) from nine locations in a single, small lake (24 km(2)), using microsatellites. We detected significant genetic differentiation in all but two pairwise comparisons. These patterns were not consistent with divergence by distance or the existence of kin groups. Instead, they suggest that cryptic barriers to dispersal exist within the lake, allowing small-scale genetic divergence. Such an observation suggests that allopatric (or parapatric) divergence may be possible, even in small, apparently homogenous environments such as lakes. This has important consequences for how we currently view evidence from nature for sympatric speciation.
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| 14. |
- Forsman, Anders, 1962-, et al.
(author)
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Rapid evolution of fire melanism in replicated populations of pygmy grasshoppers
- 2011
-
In: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 65:9, s. 2530-2540
-
Journal article (peer-reviewed)abstract
- Evolutionary theory predicts an interactive process whereby spatiotemporal environmental heterogeneity will maintain genetic variation, while genetic and phenotypic diversity will buffer populations against stress and allow for fast adaptive evolution in rapidly changing environments. Here, we study color polymorphism patterns in pygmy grasshoppers (Tetrix subulata) and show that the frequency of the melanistic (black) color variant was higher in areas that had been ravaged by fires the previous year than in nonburned habitats, that, in burned areas, the frequency of melanistic grasshoppers dropped from ca. 50% one year after a fire to 30% after four years, and that the variation in frequencies of melanistic individuals among and within populations was genetically based on and represented evolutionary modifications. Dark coloration may confer a selective benefit mediated by enhanced camouflage in recently fire-ravaged areas characterized by blackened visual backgrounds before vegetation has recovered. These findings provide rare evidence for unusually large, extremely rapid adaptive contemporary evolution in replicated natural populations in response to divergent and fluctuating selection associated with spatiotemporal environmental changes.
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| 15. |
- Gonzalez-Voyer, Alejandro, et al.
(author)
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Distinct Evolutionary Patterns of Brain and Body Size During Adaptive Radiation
- 2009
-
In: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 63:9, s. 2266-2274
-
Journal article (peer-reviewed)abstract
- Morphological traits are often genetically and/or phenotypically correlated with each other and such covariation can have an important influence on the evolution of individual traits. The strong positive relationship between brain size and body size in vertebrates has attracted a lot of interest, and much debate has surrounded the study of the factors responsible for the allometric relationship between these two traits. Here, we use comparative analyses of the Tanganyikan cichlid adaptive radiation to investigate the patterns of evolution for brain size and body size separately. We found that body size exhibited recent bursts of rapid evolution, a pattern that is consistent with divergence linked to ecological specialization. Brain weight on the other hand, showed no bursts of divergence but rather evolved in a gradual manner. Our results thus show that even highly genetically correlated traits can present markedly different patterns of evolution, hence interpreting patterns of evolution of traits from correlations in extant taxa can be misleading. Furthermore, our results suggest, contrary to expectations from theory, that brain size does not play a key role during adaptive radiation.
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| 16. |
- Gosden, Thomas, et al.
(författare)
-
The B-matrix harbors significant and sex-specific constraints on the evolution of multicharacter sexual dimorphism.
- 2012
-
Ingår i: Evolution. - : Wiley. - 1558-5646 .- 0014-3820. ; 66:7, s. 2106-2116
-
Tidskriftsartikel (refereegranskat)abstract
- The extent to which sexual dimorphism can evolve within a population depends on an interaction between sexually divergent selection and constraints imposed by a genetic architecture that is shared between males and females. The degree of constraint within a population is normally inferred from the intersexual genetic correlation, r(mf) . However, such bivariate correlations ignore the potential constraining effect of genetic covariances between other sexually coexpressed traits. Using the fruit fly Drosophila serrata, a species that exhibits mutual mate preference for blends of homologous contact pheromones, we tested the impact of between-sex between-trait genetic covariances using an extended version of the genetic variance-covariance matrix, G, that includes Lande's (1980) between-sex covariance matrix, B. We find that including B greatly reduces the degree to which male and female traits are predicted to diverge in the face of divergent phenotypic selection. However, the degree to which B alters the response to selection differs between the sexes. The overall rate of male trait evolution is predicted to decline, but its direction remains relatively unchanged, whereas the opposite is found for females. We emphasize the importance of considering the B-matrix in microevolutionary studies of constraint on the evolution of sexual dimorphism.
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| 17. |
- Harari, Ally, et al.
(författare)
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Fitness cost of pheromone production in signaling female moths
- 2011
-
Ingår i: Evolution. - : Wiley. - 1558-5646 .- 0014-3820. ; 65:6, s. 1572-1582
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Forskningsöversikt (refereegranskat)abstract
- A secondary sexual character may act as an honest signal of the quality of the individual if the trait bears a cost and if its expression is phenotypically condition dependent. The cost of increasing the trait should be tolerable for individuals in good condition but not for those in a poor condition. The trait thus provides an honest signal of quality that enables the receiver to choose higher quality mates. Evidence for sex pheromones, which play a major role in shaping sexual evolution, inflicting a signaling cost is scarce. Here, we demonstrate that the amount of the major component of the pheromone in glands of Lobesia botrana (Lepidoptera) females at signaling time was significantly greater in large than in small females, that male moths preferred larger females as mates when responding to volatile signals, and small virgin females, but not large ones, exposed to conspecific pheromone, produced, when mated, significantly fewer eggs than nonexposed females. The latter indicates a condition-dependent cost of signaling. These results are in accordance with the predictions of condition-dependent honest signals. We therefore suggest that female signaling for males using sex pheromones bears a cost and thus calling may serve as honest advertisement for female quality.
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| 18. |
- Olsson, Mats, et al.
(författare)
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A significant component of ageing (DNA damage) is reflected in fading breeding colors: an experimental test using innate antioxidant mimetics in painted dragon lizards
- 2012
-
Ingår i: Evolution. - : Wiley. - 1558-5646 .- 0014-3820. ; 66:8, s. 2475-2483
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Tidskriftsartikel (refereegranskat)abstract
- A decade ahead of their time, von Schantz et al. united sexual selection and free radical biology by identifying causal links between deep-rooted physiological processes that dictate resistance to toxic waste from oxidative metabolism (reactive oxygen species, ROS), and phenotypic traits, such as ornaments. Ten years later, these ideas have still only been tested with indirect estimates of free radical levels (oxidative stress) subsequent to the action of innate and dietary antioxidants. Here, we measure net superoxide (a selection pressure for antioxidant production) and experimentally manipulate superoxide antioxidation using a synthetic mimetic of superoxide dismutase (SOD), Eukarion 134 (EUK). We then measure the toxic effect of superoxide in terms of DNA erosion and concomitant loss of male breeding coloration in the lizard, Ctenophorus pictus. Control males suffered more DNA damage than EUK males. Spectroradiometry showed that male coloration is lost in relation to superoxide and covaries with DNA erosion; in control males, these variables explained loss of color, whereas in EUK males, the fading of coloration was unaffected by superoxide and unrelated to DNA damage. Thus, EUK's powerful antioxidation removes the erosion effect of superoxide on coloration and experimentally verifies the prediction that colors reflect innate capacity for antioxidation.
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| 19. |
- Tschirren, Barbara, et al.
(författare)
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Contrasting patterns of diversity and population differentiation at the innate immunity gene toll-like receptor 2 (tlr2) in two sympatric rodent species.
- 2012
-
Ingår i: Evolution. - : Wiley. - 1558-5646 .- 0014-3820. ; 66:3, s. 720-731
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Tidskriftsartikel (refereegranskat)abstract
- Comparing patterns of diversity and divergence between populations at immune genes and neutral markers can give insights into the nature and geographic scale of parasite-mediated selection. To date, studies investigating such patterns of selection in vertebrates have primarily focused on the acquired branch of the immune system, whereas it remains largely unknown how parasite-mediated selection shapes innate immune genes both within and across vertebrate populations. Here, we present a study on the diversity and population differentiation at the innate immune gene Toll-like receptor 2 (TLR2) across nine populations of yellow-necked mice (Apodemus flavicollis) and bank voles (Myodes glareolus) in southern Sweden. In yellow-necked mice, TLR2 diversity was very low, as was TLR2 population differentiation compared to neutral loci. In contrast, several TLR2 haplotypes co-occurred at intermediate frequencies within and across bank vole populations, and pronounced isolation by distance between populations was observed. The diversity and differentiation at neutral loci was similar in the two species. These results indicate that parasite-mediated selection has been acting in dramatically different ways on a given immune gene in ecologically similar and sympatric species. Furthermore, the finding of TLR2 population differentiation at a small geographical scale in bank voles highlights that vertebrate innate immune defense may be evolutionarily more dynamic than has previously been appreciated.
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| 20. |
- Ujvari, Beata, et al.
(författare)
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Isolation breeds naivety: island living robs Australian varanid lizards of toad-toxin immunity via four-base-pair mutation.
- 2013
-
Ingår i: Evolution: international journal of organic evolution. - : Wiley. - 1558-5646. ; 67:1, s. 289-294
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Tidskriftsartikel (refereegranskat)abstract
- Since their introduction to the toad-free Australian continent cane toads (Bufo marinus) have caused a dramatic increase in naïve varanid mortality when these large lizards attempt to feed on this toxic amphibian. In contrast Asian-African varanids, which have coevolved with toads, are resistant to toad toxin. Toad toxins, such as Bufalin target the H1-H2 domain of the α(1) subunit of the sodium-potassium-ATPase enzyme. Sequencing of this domain revealed identical nucleotide sequences in four Asian as well as in three African varanids, and identical sequences in all 11 Australian varanids. However, compared to the Asian-African varanids, the Australian varanids showed four-base-pair substitutions, resulting in the alteration in three of the 12 amino acids representing the H1-H2 domain. The phenotypic effect of the substitutions was investigated in human embryonic kidney (HEK) 293 cells stably transfected with the Australian and the Asian-African H1-H2 domains. The transfections resulted in an approximate 3000-fold reduction in resistance to Bufalin in the Australian HEK293 cells compared to the Asian-African HEK293 cells, demonstrating the critical role of this minor mutation in providing Bufalin resistance. Our study hence presents a clear link between genotype and phenotype, a critical step in understanding the evolution of phenotypic diversity.
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| 21. |
- Wellenreuther, Maren, et al.
(författare)
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Simulating range expansion: male species recognition and loss of premating isolation in damselflies
- 2010
-
Ingår i: Evolution: international journal of organic evolution. - : Wiley. - 1558-5646. ; 64, s. 242-252
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Tidskriftsartikel (refereegranskat)abstract
- Prolonged periods of allopatry might result in loss of the ability to discriminate against other formerly sympatric species, and can lead to heterospecific matings and hybridization upon secondary contact. Loss of premating isolation during prolonged allopatry can operate in the opposite direction of reinforcement, but has until now been little explored. We investigated how premating isolation between two closely related damselfly species, Calopteryx splendens and C. virgo, might be affected by the expected future northward range expansion of C. splendens into the allopatric zone of C. virgo in northern Scandinavia. We simulated the expected secondary contact by presenting C. splendens females to C. virgo males in the northern allopatric populations in Finland. Premating isolation towards C. splendens in northern allopatric populations was compared to sympatric populations in southern Finland and southern Sweden. Male courtship responses of C. virgo towards conspecific females showed limited geographic variation, however, courtship attempts towards heterospecific C. splendens females increased significantly from sympatry to allopatry. Our results suggest that allopatric C. virgo males have partly lost their ability to discriminate against heterospecific females. Reduced premating isolation in allopatry might lead to increased heterospecific matings between taxa that are currently expanding and shifting their ranges in response to climate change.
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| 22. |
- Anderson, Bruce, et al.
(författare)
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Evolution and coexistence of pollination ecotypes in an African Gladiolus (Iridaceae)
- 2010
-
Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 64:4, s. 960-972
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Tidskriftsartikel (refereegranskat)abstract
- Pollinator-mediated selection has been suggested as a key driver of speciation in plants. We examined the potential role of hawkmoth pollinators in driving allopatric divergence and maintaining sympatric coexistence of morphotypes in the African iris Gladiolus longicollis. Floral tube length in this species varies from 35 mm to 130 mm across its geographic range and reflects the prevailing tongue lengths of local hawkmoth assemblages. The distribution of floral tube lengths is bimodal with two relatively discrete categories—long (about 90 mm) or short (about 50 mm)—that match the bimodal distribution of hawkmoth tongue lengths in eastern South Africa. At a contact site between these two floral morphs, we found few individuals of intermediate length, suggesting limited gene flow between morphs despite their interfertility. A difference in flowering phenology appears to be the main isolating barrier between morphs at this site. Long- and short-tubed morphs differed markedly in the chemical composition of their floral fragrance, a trait that could be used as a cue for morph-specific foraging by hawkmoths. Positive directional selection on tube length was found to occur in both morphs.
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| 23. |
- Antoniazza, Sylvain, et al.
(författare)
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Local adaptation maintains clinal variation in melanin-based coloration of European barn owls (Tyto alba).
- 2010
-
Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 64:7, s. 1944-1954
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Tidskriftsartikel (refereegranskat)abstract
- Ecological parameters vary in space, and the resulting heterogeneity of selective forces can drive adaptive population divergence. Clinal variation represents a classical model to study the interplay of gene flow and selection in the dynamics of this local adaptation process. Although geographic variation in phenotypic traits in discrete populations could be remainders of past adaptation, maintenance of adaptive clinal variation requires recurrent selection. Clinal variation in genetically determined traits is generally attributed to adaptation of different genotypes to local conditions along an environmental gradient, although it can as well arise from neutral processes. Here, we investigated whether selection accounts for the strong clinal variation observed in a highly heritable pheomelanin-based color trait in the European barn owl by comparing spatial differentiation of color and of neutral genes among populations. Barn owl's coloration varies continuously from white in southwestern Europe to reddish-brown in northeastern Europe. A very low differentiation at neutral genetic markers suggests that substantial gene flow occurs among populations. The persistence of pronounced color differentiation despite this strong gene flow is consistent with the hypothesis that selection is the primary force maintaining color variation among European populations. Therefore, the color cline is most likely the result of local adaptation.
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| 24. |
- Archer, C. R., et al.
(författare)
-
Sexual selection affects the evolution of lifespan and ageing in the decorated cricket gryllodes sigillatus
- 2012
-
Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 66:10, s. 3088-3100
-
Tidskriftsartikel (refereegranskat)abstract
- Recent work suggests that sexual selection can influence the evolution of ageing and lifespan by shaping the optimal timing and relative costliness of reproductive effort in the sexes. We used inbred lines of the decorated cricket, Gryllodes sigillatus, to estimate the genetic (co)variance between age-dependent reproductive effort, lifespan, and ageing within and between the sexes. Sexual selection theory predicts that males should die sooner and age more rapidly than females. However, a reversal of this pattern may be favored if reproductive effort increases with age in males but not in females. We found that male calling effort increased with age, whereas female fecundity decreased, and that males lived longer and aged more slowly than females. These divergent life-history strategies were underpinned by a positive genetic correlation between early-life reproductive effort and ageing rate in both sexes, although this relationship was stronger in females. Despite these sex differences in life-history schedules, age-dependent reproductive effort, lifespan, and ageing exhibited strong positive intersexual genetic correlations. This should, in theory, constrain the independent evolution of these traits in the sexes and may promote intralocus sexual conflict. Our study highlights the importance of sexual selection to the evolution of sex differences in ageing and lifespan in G. sigillatus.
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| 25. |
- Arnqvist, Göran
(författare)
-
Assortative mating by fitness and sexually antagonistic genetic variation
- 2011
-
Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 65:7, s. 2111-2116
-
Tidskriftsartikel (refereegranskat)abstract
- Recent documentations of sexually antagonistic genetic variation in fitness have spurred an interest in the mechanisms that may act to maintain such variation in natural populations. Using individual-based simulations, I show that positive assortative mating by fitness increases the amount of sexually antagonistic genetic variance in fitness, primarily by elevating the equilibrium frequency of heterozygotes, over most of the range of sex-specific selection and dominance. Further, although the effects of assortative mating by fitness on the protection conditions of polymorphism in sexually antagonistic loci were relatively minor, it widens the protection conditions under most reasonable scenarios (e. g., under heterozygote superiority when fitness is averaged across the sexes) but can also somewhat narrow the protection conditions under other circumstances. The near-ubiquity of assortative mating in nature suggests that it may contribute to upholding standing sexually antagonistic genetic variation in fitness.
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| 26. |
- Arnqvist, Göran, et al.
(författare)
-
Genetic architecture of metabolic rate : environment specific epistasis between mitochondrial and nuclear genes in an insect
- 2010
-
Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 64:12, s. 3354-3363
-
Tidskriftsartikel (refereegranskat)abstract
- The extent to which mitochondrial DNA (mtDNA) variation is involved in adaptive evolutionary change is currently being reevaluated. In particular, emerging evidence suggests that mtDNA genes coevolve with the nuclear genes with which they interact to form the energy producing enzyme complexes in the mitochondria. This suggests that intergenomic epistasis between mitochondrial and nuclear genes may affect whole-organism metabolic phenotypes. Here, we use crossed combinations of mitochondrial and nuclear lineages of the seed beetle Callosobruchus maculatus and assay metabolic rate under two different temperature regimes. Metabolic rate was affected by an interaction between the mitochondrial and nuclear lineages and the temperature regime. Sequence data suggests that mitochondrial genetic variation has a role in determining the outcome of this interaction. Our genetic dissection of metabolic rate reveals a high level of complexity, encompassing genetic interactions over two genomes, and genotype x genotype x environment interactions. The evolutionary implications of these results are twofold. First, because metabolic rate is at the root of life histories, our results provide insights into the complexity of life-history evolution in general, and thermal adaptation in particular. Second, our results suggest a mechanism that could contribute to the maintenance of nonneutral mtDNA polymorphism.
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| 27. |
- Balogh, Alexandra C.V., et al.
(författare)
-
Feature theory and the two-step hypothesis of Müllerian mimicry evolution
- 2010
-
Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 64:3, s. 810-822
-
Tidskriftsartikel (refereegranskat)abstract
- The two-step hypothesis of Müllerian mimicry evolution states that mimicry starts with a major mutational leap between adaptive peaks, followed by gradual fine-tuning. The hypothesis was suggested to solve the problem of apostatic selection producing a valley between adaptive peaks, and appears reasonable for a one-dimensional phenotype. Extending the hypothesis to the realistic scenario of multidimensional phenotypes controlled by multiple genetic loci can be problematic, because it is unlikely that major mutational leaps occur simultaneously in several traits. Here we consider the implications of predator psychology on the evolutionary process. According to feature theory, single prey traits may be used by predators as features to classify prey into discrete categories. A mutational leap in such a trait could initiate mimicry evolution. We conducted individual-based evolutionary simulations in which virtual predators both categorize prey according to features and generalize over total appearances. We found that an initial mutational leap towards feature similarity in one dimension facilitates mimicry evolution of multidimensional traits. We suggest that feature-based predator categorization together with predator generalization over total appearances solves the problem of applying the two-step hypothesis to complex phenotypes, and provides a basis for a theory of the evolution of mimicry rings.
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| 28. |
- Barnes, Ian, et al.
(författare)
-
Ancient urbanization predicts genetic resistance to tuberculosis
- 2011
-
Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 65:3, s. 842-848
-
Tidskriftsartikel (refereegranskat)abstract
- A link between urban living and disease is seen in recent and historical records, but the presence of this association in prehistory has been difficult to assess. If the transition to urban living does result in an increase in disease-based mortality, we might expect to see evidence of increased disease resistance in longer-term urbanized populations, as the result of natural selection. To test this, we determined the frequency of an allele (SLC11A1 1729 + 55del4) associated with natural resistance to intracellular pathogens such as tuberculosis and leprosy. We found a highly significantly correlation with duration of urban settlement-populations with a long history of living in towns are better adapted to resisting these infections. This correlation remains strong when we correct for autocorrelation in allele frequencies due to shared population history. Our results therefore support the interpretation that infectious disease loads became an increasingly important cause of human mortality after the advent of urbanization, highlighting the importance of population density in determining human health and the genetic structure of human populations.
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| 29. |
- Bokma, Folmer
(författare)
-
Detection of "punctuated equilibrium" by Bayesian estimation of speciation and extinction rates, ancestral character states, and rates of anagenetic and cladogenetic evolution on a molecular phylogeny
- 2008
-
Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 62:11, s. 2718-26
-
Tidskriftsartikel (refereegranskat)abstract
- Speciation and extinction probabilities can be estimated from molecular phylogenies of extant species that are complete at the species level. Because only a fraction of published phylogenies is complete at the species level, methods have been developed to estimate speciation and extinction probabilities also from incomplete phylogenies. However, due to different estimation techniques, estimates from complete and incomplete phylogenies are difficult to compare statistically. Here I show with some examples how existing likelihood functions can be used to obtain Bayesian estimates of speciation and extinction probabilities, and how this approach is applied to both complete and incomplete phylogenies.
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| 30. |
- Bokma, Folmer, et al.
(författare)
-
Unexpectedly many extinct hominins
- 2012
-
Ingår i: Evolution. - Hoboken, NJ : Wiley-Blackwell. - 0014-3820 .- 1558-5646. ; 66:9, s. 2969-2974
-
Tidskriftsartikel (refereegranskat)abstract
- Recent studies indicate that Neanderthal and Denisova hominins may have been separate species, while debate continues on the status of Homo floresiensis. The decade-long debate between splitters, who recognize over 20 hominin species, and lumpers, who maintain that all these fossils belong to just a few lineages, illustrates that we do not know how many extinct hominin species to expect. Here, we present probability distributions for the number of speciation events and the number of contemporary species along a branch of a phylogeny. With estimates of hominin speciation and extincton rates, we then show that the expected total number of extinct hominin species is 8, but may be as high as 27. We also show that it is highly unlikely that three very recent species disappeared due to natural, background extinction. This may indicate that human-like remains are too easily considered distinct species. Otherwise, the evidence suggesting that Neanderthal and the Denisova hominin represent distinct species implies a recent wave of extinctions, ostensibly driven by the only survivor, H. sapiens.
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| 31. |
- Cayetano, Luis, et al.
(författare)
-
Evolution of male and female genitalia following release from sexual selection
- 2011
-
Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 65:8, s. 2171-2183
-
Tidskriftsartikel (refereegranskat)abstract
- Despite the key functions of the genitalia in sexual interactions and fertilization, the role of sexual selection and conflict in shaping genital traits remains poorly understood. Seed beetle (Callosobruchus maculatus) males possess spines on the intromittent organ, and females possess a thickened reproductive tract wall that also bears spines. We investigated the role of sexual selection and conflict by imposing monogamous mating on eight replicate populations of this naturally polygamous insect, while maintaining eight other populations under polygamy. To establish whether responses to mating system manipulation were robust to ecological context, we simultaneously manipulated life-history selection (early/late reproduction). Over 18-21 generations, male genital spines evolved relatively reduced length in large males (i.e., shallower static allometry) in monogamous populations. Two nonintromittent male genital appendages also evolved in response to the interaction of mating system and ecology. In contrast, no detectable evolution occurred in female genitalia, consistent with the expectation of a delayed response in defensive traits. Our results support a sexually antagonistic role for the male genital spines, and demonstrate the evolution of static allometry in response to variation in sexual selection opportunity. We argue that further advances in the study of genital coevolution will require a much more detailed understanding of the functions of male and female genital traits.
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| 32. |
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| 33. |
- Engen, Steinar, et al.
(författare)
-
Effective size of fluctuating populations with two sexes and overlapping generations
- 2007
-
Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 61:8, s. 1873-1885
-
Tidskriftsartikel (refereegranskat)abstract
- We derive formulas that can be applied to estimate the effective population size N(e) for organisms with two sexes reproducing once a year and having constant adult mean vital rates independent of age. Temporal fluctuations in population size are generated by demographic and environmental stochasticity. For populations with even sex ratio at birth, no deterministic population growth and identical mean vital rates for both sexes, the key parameter determining N(e) is simply the mean value of the demographic variance for males and females considered separately. In this case Crow and Kimura's generalization of Wright's formula for N(e) with two sexes, in terms of the effective population sizes for each sex, is applicable even for fluctuating populations with different stochasticity in vital rates for males and females. If the mean vital rates are different for the sexes then a simple linear combination of the demographic variances determines N(e), further extending Wright's formula. For long-lived species an expression is derived for N(e) involving the generation times for both sexes. In the general case with nonzero population growth and uneven sex ratio of newborns, we use the model to investigate numerically the effects of different population parameters on N(e). We also estimate the ratio of effective to actual population size in six populations of house sparrows on islands off the coast of northern Norway. This ratio showed large interisland variation because of demographic differences among the populations. Finally, we calculate how N(e) in a growing house sparrow population will change over time.
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| 34. |
- Fitzpatrick, J. L., et al.
(författare)
-
Male Contest Competition And The Coevolution Of Weaponry And Testes In Pinnipeds
- 2012
-
Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 66:11, s. 3595-3604
-
Tidskriftsartikel (refereegranskat)abstract
- Male reproductive success is influenced by competitive interactions during precopulatory and postcopulatory selective episodes. Consequently, males can gain reproductive advantages during precopulatory contest competition by investing in weaponry and during postcopulatory sperm competition by investing in ejaculates. However, recent theory predicts male expenditure on weaponry and ejaculates should be subject to a trade-off, and should vary under increasing risk and intensity of sperm competition. Here, we provide the first comparative analysis of the prediction that expenditure on weaponry should be negatively associated with expenditure on testes mass. Specifically, we assess how sexual selection influences the evolution of primary and secondary sexual traits among pinnipeds (seals, sea lions, and walruses). Using recently developed comparative methods, we demonstrate that sexual selection promotes rapid divergence in body mass, sexual size dimorphism (SSD), and genital morphology. We then show that genital length appears to be positively associated with the strength of postcopulatory sexual selection. However, subsequent analyses reveal that both genital length and testes mass are negatively associated with investment in precopulatory weaponry. Thus, our results are congruent with recent theoretical predictions of contest-based sperm competition models. We discuss the possible role of trade-offs and allometry in influencing patterns of reproductive trait evolution in pinnipeds.
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| 35. |
- Fitzpatrick, John L, et al.
(författare)
-
Polyandry reduces sperm length variation in social insects.
- 2011
-
Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 65:10
-
Tidskriftsartikel (refereegranskat)abstract
- Postcopulatory sexual selection, either in the form of sperm competition or cryptic female choice, is an important selective force that is thought to have generated the enormous variation in sperm morphology observed interspecifically. However, the evolutionary significance of intraspecific variation in sperm morphology, and the role that postcopulatory sexual selection plays in influencing this variation, remains poorly investigated in invertebrates. Here, we tested the hypothesis that postcopulatory sexual selection reduces variation in sperm morphology, both between and within males, in 27 species of eusocial ants and bees. These eusocial species offer an unusual opportunity to assess how selection acts on variance in sperm morphology, as haploid males produce clonal, haploid sperm that does not experience haploid-diploid conflict. We provide solid evidence that males of polyandrous ant and bee species indeed produce less-variable sperm, indicating that sperm competition selected for sperm of superior quality. Our results offer a mechanistic explanation for the evolution of high-quality sperm and provide comprehensive evidence that sperm morphology of social insects is influenced by sexual selection.
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| 36. |
- Fogarty, Laurel, et al.
(författare)
-
THE EVOLUTION OF TEACHING
- 2011
-
Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 65:10, s. 2760-2770
-
Tidskriftsartikel (refereegranskat)abstract
- Teaching, alongside imitation, is widely thought to underlie the success of humanity by allowing high-fidelity transmission of information, skills, and technology between individuals, facilitating both cumulative knowledge gain and normative culture. Yet, it remains a mystery why teaching should be widespread in human societies but extremely rare in other animals. We explore the evolution of teaching using simple genetic models in which a single tutor transmits adaptive information to a related pupil at a cost. Teaching is expected to evolve where its costs are outweighed by the inclusive fitness benefits that result from the tutor's relatives being more likely to acquire the valuable information. We find that teaching is not favored where the pupil can easily acquire the information on its own, or through copying others, or for difficult to learn traits, where teachers typically do not possess the information to pass on to relatives. This leads to a narrow range of traits for which teaching would be efficacious, which helps to explain the rarity of teaching in nature, its unusual distribution, and its highly specific nature. Further models that allow for cumulative cultural knowledge gain suggest that teaching evolved in humans because cumulative culture renders otherwise difficult-to-acquire valuable information available to teach.
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| 37. |
- Forest, F., et al.
(författare)
-
The role of biotic and abiotic factors in evolution of ant dispersal in the milkwort family (Polygalaceae)
- 2007
-
Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 61:7, s. 1675-1694
-
Tidskriftsartikel (refereegranskat)abstract
- A phylogenetic approach was taken to investigate the evolutionary history of seed appendages in the plant family Polygalaceae (Fabales) and determine which factors might be associated with evolution of elaiosomes through comparisons to abiotic (climate) and biotic (ant species number and abundance) timelines. Molecular datasets from three plastid regions representing 160 species were used to reconstruct a phylogenetic tree of the order Fabales, focusing on Polygalaceae. Bayesian dating methods were used to estimate the age of the appearance of ant-dispersed elaiosomes in Polygalaceae, shown by likelihood optimizations to have a single origin in the family. Topology-based tests indicated a diversification rate shift associated with appearance of caruncular elaiosomes. We show that evolution of the caruncular elaiosome type currently associated with ant dispersal occurred 54.0-50.5 million year ago. This is long after an estimated increase in ant lineages in the Late Cretaceous based on molecular studies, but broadly concomitant with increasing global temperatures culminating in the Late Paleocene-Early Eocene thermal maxima. These results suggest that although most major ant clades were present when elaiosomes appeared, the environmental significance of elaiosomes may have been an important factor in success of elaiosome-bearing lineages. Ecological abundance of ants is perhaps more important than lineage numbers in determining significance of ant dispersal. Thus, our observation that elaiosomes predate increased ecological abundance of ants inferred from amber deposits could be indicative of an initial abiotic environmental function.
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| 38. |
- Fricke, Claudia, et al.
(författare)
-
Rapid adaptation to a novel host in a seed beetle (Callosobruchus maculatus) : the role of sexual selection
- 2007
-
Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 61:2, s. 440-454
-
Tidskriftsartikel (refereegranskat)abstract
- Rapid diversification is common among herbivorous insects and is often the result of host shifts, leading to the exploitation of novel food sources. This, in turn, is associated with adaptive evolution of female oviposition behavior and larval feeding biology. Although natural selection is the typical driver of such adaptation, the role of sexual selection is less clear. In theory, sexual selection can either accelerate or impede adaptation. To assess the independent effects of natural and sexual selection on the rate of adaptation, we performed a laboratory natural selection experiment in a herbivorous bruchid beetle (Callosobruchus maculatus). We established replicated selection lines where we varied natural (food type) and sexual (mating system) selection in a 2 × 2 orthogonal design, and propagated our lines for 35 generations. In half of the lines, we induced a host shift whereas the other half was kept on the ancestral host. We experimentally enforced monogamy in half of the lines, whereas the other half remained polygamous. The beetles rapidly adapted to the novel host, which primarily involved increased host acceptance by females and an accelerated rate of larval development. We also found that our mating system treatment affected the rate of adaptation, but that this effect was contingent upon food type. As beetles adapted to the novel host, sexual selection reinforced natural selection whereas populations residing close to their adaptive peak (i.e., those using their ancestral host) exhibited higher fitness in the absence of sexual selection. We discuss our findings in light of current sexual selection theory and suggest that the net evolutionary effect of reproductive competition may critically depend on natural selection. Sexual selection may commonly accelerate adaptation under directional natural selection whereas sexual selection, and the associated load brought by sexual conflict, may tend to depress population fitness under stabilizing natural selection.
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| 39. |
- Grieshop, Karl, et al.
(författare)
-
The Precopulatory Function of Male Genital Spines in Drosophila Ananassae [Doleschall] (Diptera: Drosophilidae) Revealed by Laser Surgery
- 2012
-
Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 66:8, s. 2637-2645
-
Tidskriftsartikel (refereegranskat)abstract
- That male genital morphology evolves via postcopulatory sexual selection is a widely held view. In contrast, the precopulatory sexual selection hypothesis for genital evolution has received less attention. Here, we test the hypothesis that male genital spines of Drosophila ananassae promote competitive male copulation success. Using laser surgery to manipulate trait size, we demonstrate that incremental reductions of spine length progressively reduce male copulation success: males without spines failed entirely to copulate because of an inability to couple the genitalia together, whereas males with halfway ablated and blunted spines suffered reductions in copulation success of 87% and 13%, respectively. The decrease in copulation success resulting from spine length reduction was markedly stronger in sexually competitive environments than in noncompetitive environments, and females expressed resistance behaviors similarly toward competing male treatments, demonstrating directly the role of genital spines in promoting competitive copulation success. Because these spines are widespread within Drosophila, and because genital traits with precopulatory function are being discovered in a growing number of animal taxa, precopulatory sexual selection may have a more pervasive role in genital evolution than previously recognized.
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| 40. |
- Hall, David, 1974-, et al.
(författare)
-
Adaptive population differentiation in phenology across a latitudinal gradient in European aspen (Populus tremula, L.) : a comparison of neutral markers, candidate genes and phenotypic traits
- 2007
-
Ingår i: Evolution. - : Wiley InterScience. - 0014-3820 .- 1558-5646. ; 61, s. 2849-2860
-
Tidskriftsartikel (refereegranskat)abstract
- A correct timing of growth cessation and dormancy induction represents a critical ecological and evolutionary trade-off between survival and growth in most forest trees (Rehfeldt et al. 1999; Horvath et al. 2003; Howe et al. 2003). We have studied the deciduous tree European Aspen (Populus tremula) across a latitudinal gradient and compared genetic differentiation in phenology traits with molecular markers. Trees from 12 different areas covering 10 latitudinal degrees were cloned and planted in two common gardens. Several phenology traits showed strong genetic differentiation and clinal variation across the latitudinal gradient, with QST values generally exceeding 0.5. This is in stark contrast to genetic differentiation at several classes of genetic markers (18 neutral SSRs, 7 SSRs located close to phenology candidate genes and 50 SNPs from five phenology candidate genes) that all showed FST values around 0.015. We thus find strong evidence for adaptive divergence in phenology traits across the latitudinal gradient. However, the strong population structure seen at the quantitative traits is not reflected in underlying candidate genes. This result fit theoretical expectations that suggest that genetic differentiation at candidate loci is better described by FST at neutral loci rather than by QST at the quantitative traits themselves.
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| 41. |
- Husby, Arild, et al.
(författare)
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Sex chromosome linked genetic variance and the evolution of sexual dimorphism of quantitative traits
- 2013
-
Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 67:3, s. 609-619
-
Tidskriftsartikel (refereegranskat)abstract
- Theory predicts that sex chromsome linkage should reduce intersexual genetic correlations thereby allowing the evolution of sexual dimorphism. Empirical evidence for sex linkage has come largely from crosses and few studies have examined how sexual dimorphism and sex linkage are related within outbred populations. Here, we use data on an array of different traits measured on over 10,000 individuals from two pedigreed populations of birds (collared flycatcher and zebra finch) to estimate the amount of sex-linked genetic variance (h2z). Of 17 traits examined, eight showed a nonzero h2Z estimate but only four were significantly different from zero (wing patch size and tarsus length in collared flycatchers, wing length and beak color in zebra finches). We further tested how sexual dimorphism and the mode of selection operating on the trait relate to the proportion of sex-linked genetic variance. Sexually selected traits did not show higher h2Z than morphological traits and there was only a weak positive relationship between h2Z and sexual dimorphism. However, given the relative scarcity of empirical studies, it is premature to make conclusions about the role of sex chromosome linkage in the evolution of sexual dimorphism.
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| 42. |
- Ingram, Travis, et al.
(författare)
-
Intraguild predation drives evolutionary niche shift in threespine stickleback
- 2012
-
Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 66:6, s. 1819-1832
-
Tidskriftsartikel (refereegranskat)abstract
- Intraguild predation—competition and predation by the same antagonist—is widespread, but its evolutionary consequences are unknown. Intraguild prey may evolve antipredator defenses, superior competitive ability on shared resources, or the ability to use an alternative resource, any of which may alter the structure of the food web. We tested for evolutionary responses by threespine stickleback to a benthic intraguild predator, prickly sculpin. We used a comparative morphometric analysis to show that stickleback sympatric with sculpin are more armored and have more limnetic-like body shapes than allopatric stickleback. To test the ecological implications of this shift, we conducted a mesocosm experiment that varied sculpin presence and stickleback population of origin (from one sympatric and one allopatric lake). Predation by sculpin greatly increased the mortality of allopatric stickleback. In contrast, sculpin presence did not affect the mortality of sympatric stickleback, although they did have lower growth rates suggesting increased nonpredatory effects of sculpin. Consistent with their morphology, sympatric stickleback included more pelagic prey in their diets, leading to depletion of zooplankton in the mesocosms. These findings suggest that intraguild prey evolution has altered food web structure by reducing both predation by the intraguild predator and diet overlap between species
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| 43. |
- James, Timothy Y., et al.
(författare)
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Evolutionary significance of imbalanced nuclear ratios within heterokaryons of the basidiomycete fungus Heterobasidion parviporum
- 2008
-
Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 62:9, s. 2279-2296
-
Tidskriftsartikel (refereegranskat)abstract
- Many fungi have heterokaryotic life stages in which genetically different nuclei inhabit the same cell. In basidiomycetes, the heterokaryon is the product of mating and represents a genomic union very similar to a diploid thallus, yet the maintenance of unfused nuclei suggests a more complex association of the two genomes relative to diploidy. In species with variable numbers of nuclei per heterokaryotic cell, nuclear ratios within a mycelium may possibly become imbalanced (differ from 1:1) due to nuclear competition. In this study, heterokaryons of the basidiomycete Heterobasidion parviporum were examined to determine the effects of genotype and environment on nuclear ratios within vegetative mycelia. The data reveal that nuclear ratios are frequently imbalanced, generally stable over time, and genetically determined. The nuclear ratios were affected by environment, but the observed nuclear ratios did not follow the expectations of strong selection acting on a population of nuclei. Instead, these ratios were largely driven by genetic effects and epigenetic effects. Finally, the data suggest that nuclear ratio imbalance also affects both gene transcription and growth rate, implying that heterokaryotic basidiomycetes are not functionally equivalent to diploid individuals and have a higher potential for genotypic and phenotypic variation.
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| 44. |
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| 45. |
- Johansson, Ulf S, et al.
(författare)
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Build-up of the Himalayan avifauna through immigration : A biogeographical analysis of the Phylloscopus and Seicercus warblers
- 2007
-
Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 61:2, s. 324-333
-
Tidskriftsartikel (refereegranskat)abstract
- The Himalayan mountain range is one of the most species-rich areas in the world, harboring about 8% of the world's bird species. In this study, we compare the relative importance of immigration versus in situ speciation to the build-up of the Himalayan avifauna, by evaluating the biogeographic history of the Phylloscopus/Seicercus warblers, a speciose clade that is well represented in Himalayan forests. We use a comprehensive, multigene phylogeny in conjunction with dispersal-vicariance analysis to discern patterns of speciation and dispersal within this clade. The results indicate that virtually no speciation has occurred within the Himalayas. Instead, several speciation events are attributed to dispersal into the Himalayas followed by vicariance between the Himalayas and China/Southeast Asia. Most, perhaps all, of these events appear to be pre-Pleistocene. The apparent lack of speciation within the Himalayas stands in contrast to the mountain-driven Pleistocene speciation suggested for the Andes and the East African mountains.
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| 46. |
- Korall, Petra, et al.
(författare)
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ABRUPT DECELERATION OF MOLECULAR EVOLUTION LINKED TO THE ORIGIN OF ARBORESCENCE IN FERNS
- 2010
-
Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 64:9, s. 2786-2792
-
Tidskriftsartikel (refereegranskat)abstract
- Molecular rate heterogeneity, whereby rates of molecular evolution vary among groups of organisms, is a well-documented phenomenon. Nonetheless, its causes are poorly understood. For animals, generation time is frequently cited because longer-lived species tend to have slower rates of molecular evolution than their shorter-lived counterparts. Although a similar pattern has been uncovered in flowering plants, using proxies such as growth form, the underlying process has remained elusive. Here, we find a deceleration of molecular evolutionary rate to be coupled with the origin of arborescence in ferns. Phylogenetic branch lengths within the ""tree fern"" clade are considerably shorter than those of closely related lineages, and our analyses demonstrate that this is due to a significant difference in molecular evolutionary rate. Reconstructions reveal that an abrupt rate deceleration coincided with the evolution of the long-lived tree-like habit at the base of the tree fern clade. This suggests that a generation time effect may well be ubiquitous across the green tree of life, and that the search for a responsible mechanism must focus on characteristics shared by all vascular plants. Discriminating among the possibilities will require contributions from various biological disciplines, but will be necessary for a full appreciation of molecular evolution.
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| 47. |
- Lind, Martin, 1980-, et al.
(författare)
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Costs and limits of phenotypic plasticity in island populations of the common frog Rana temporaria under divergent selection pressures
- 2009
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Ingår i: Evolution. - : John Wiley & Sons, Inc.. - 0014-3820 .- 1558-5646. ; 63:6, s. 1508-1518
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Tidskriftsartikel (refereegranskat)abstract
- Costs and limits are assumed to be the major constraints on the evolution of phenotypic plasticity. However, despite their expected importance, they have been surprisingly hard to find in natural populations. It has therefore been argued that natural selection might have removed high-cost genotypes in all populations. However, if costs of plasticity are linked to the degree of plasticity expressed, then high costs of plasticity would only be present in populations where increased plasticity is under selection. We tested this hypothesis by investigating costs and limits of adaptive phenotypic plasticity in development time in a common garden study of island populations of the common frog Rana temporaria, which have varying levels of development time and phenotypic plasticity. Costs of plasticity were only found in populations with high-plastic genotypes, whereas the populations with the most canalized genotypes instead had a cost of canalization. Moreover, individuals displaying the most extreme phenotypes also were the most plastic ones, which mean we found no limits of plasticity. This suggests that costs of plasticity increase with increased level of plasticity in the populations, and therefore costs of plasticity might be more commonly found in high-plastic populations.
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| 48. |
- Lind, Martin I., Dr, et al.
(författare)
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Gene flow and selection on phenotypic plasticity in an island system of rana temporaria
- 2011
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Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 65:3, s. 684-697
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Tidskriftsartikel (refereegranskat)abstract
- Gene flow is often considered to be one of the main factors that constrains local adaptation in a heterogeneous environment. However, gene flow may also lead to the evolution of phenotypic plasticity. We investigated the effect of gene flow on local adaptation and phenotypic plasticity in development time in island populations of the common frog Rana temporaria which breed in pools that differ in drying regimes. This was done by investigating associations between traits (measured in a common garden experiment) and selective factors (pool drying regimes and gene flow from other populations inhabiting different environments) by regression analyses and by comparing pairwise F(ST) values (obtained from microsatellite analyses) with pairwise Q(ST) values. We found that the degree of phenotypic plasticity was positively correlated with gene flow from other populations inhabiting different environments (among-island environmental heterogeneity), as well as with local environmental heterogeneity within each population. Furthermore, local adaptation, manifested in the correlation between development time and the degree of pool drying on the islands, appears to have been caused by divergent selection pressures. The local adaptation in development time and phenotypic plasticity is quite remarkable, because the populations are young (less than 300 generations) and substantial gene flow is present among islands.
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| 49. |
- Luquet, Emilien, et al.
(författare)
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Genetic Erosion In Wild Populations Makes Resistance To A Pathogen More Costly : Genetic Erosion Makes Resistance More Costly
- 2012
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Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 66:6, s. 1942-1952
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Tidskriftsartikel (refereegranskat)abstract
- Populations that have suffered from genetic erosion are expected to exhibit reduced average trait values or decreased variation in adaptive traits when experiencing periodic or emergent stressors such as infectious disease. Genetic erosion may consequentially modify the ability of a potential host population to cope with infectious disease emergence. We experimentally investigate this relationship between genetic variability and host response to exposure to an infectious agent both in terms of susceptibility to infection and indirect parasite-mediated responses that also impact fitness. We hypothesized that the deleterious consequences of exposure to the pathogen (Batrachochytrium dendrobatidis) would be more severe for tadpoles descended from European treefrog (Hyla arborea)populations lacking genetic variability. Although all exposed tadpoles lacked detectable infection, we detected this relationship for some indirect host responses, predominantly in genetically depleted animals, as well as an interaction between genetic variability and pathogen dose on life span during the postmetamorphic period. Lack of infection and a decreased mass and postmetamorphic life span in lowgenetic diversity tadpoles lead us to conclude that genetic erosion, while not affecting the ability tomount effective resistance strategies, also erodes the capacity to invest in resistance, increased tadpole growth rate, and metamorphosis relatively simultaneously.
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| 50. |
- Martínez-Abadías, Neus, et al.
(författare)
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PERVASIVE GENETIC INTEGRATION DIRECTS THE EVOLUTION OF HUMAN SKULL SHAPE
- 2012
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Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 66:4, s. 1010-1023
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Tidskriftsartikel (refereegranskat)abstract
- It has long been unclear whether the different derived cranial traits of modern humans evolved independently in response to separate selection pressures or whether they resulted from the inherent morphological integration throughout the skull. In a novel approach to this issue, we combine evolutionary quantitative genetics and geometric morphometrics to analyze genetic and phenotypic integration in human skull shape. We measured human skulls in the ossuary of Hallstatt (Austria), which offer a unique opportunity because they are associated with genealogical data. Our results indicate pronounced covariation of traits throughout the skull. Separate simulations of selection for localized shape changes corresponding to some of the principal derived characters of modern human skulls produced outcomes that were similar to each other and involved a joint response in all of these traits. The data for both genetic and phenotypic shape variation were not consistent with the hypothesis that the face, cranial base, and cranial vault are completely independent modules but relatively strongly integrated structures. These results indicate pervasive integration in the human skull and suggest a reinterpretation of the selective scenario for human evolution where the origin of any one of the derived characters may have facilitated the evolution of the others.
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