| 1. |
- Johansson, Jacob
(författare)
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Evolutionary responses to environmental changes: How does competition affect adaptation?
- 2008
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Ingår i: Evolution. - : Wiley. - 1558-5646 .- 0014-3820. ; 62:2, s. 421-435
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Tidskriftsartikel (refereegranskat)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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| 2. |
- Kuchta, Shawn, et al.
(författare)
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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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Ingår i: Evolution. - : Wiley. - 1558-5646 .- 0014-3820. ; 62:4, s. 984-990
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Tidskriftsartikel (refereegranskat)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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| 3. |
- Svensson, Erik, et al.
(författare)
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Intralocus Sexual Conflict over Immune Defense, Gender Load and Sex-Specific Signaling in a Natural Lizard Population.
- 2009
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Ingår i: Evolution. - : Wiley. - 1558-5646 .- 0014-3820. ; 63:12, s. 3124-3135
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Tidskriftsartikel (refereegranskat)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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| 4. |
- Bergek, Sara, 1979-, et al.
(författare)
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Cryptic barriers to dispersal within a lake allow genetic differentiation of Eurasian perch
- 2007
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Ingår i: Evolution. - Oxford : Wiley-Blackwell. - 0014-3820 .- 1558-5646. ; 61:8, s. 2035-2041
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Tidskriftsartikel (refereegranskat)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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| 5. |
- Gonzalez-Voyer, Alejandro, et al.
(författare)
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Distinct Evolutionary Patterns of Brain and Body Size During Adaptive Radiation
- 2009
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Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 63:9, s. 2266-2274
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Tidskriftsartikel (refereegranskat)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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| 6. |
- Forsman, Anders, et al.
(författare)
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Calling is an honest indicator of paternal genetic quality in male poison frogs
- 2006
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Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 60:10, s. 2148-2157
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Tidskriftsartikel (refereegranskat)abstract
- Several competing hypotheses have been put forward to explain why females of many species mate preferentially with males possessing the most conspicuous signals (e.g., ornaments, displays, or songs). We performed a laboratory experiment using two species of poison frogs, Dendrobates leucomelas and Epipedobates tricolor, to test the hypothesis that male calling performance is an honest indicator of parental quality. Our analyses are based on data from behavioral observations of mating activities of captive-reared individuals (and their offspring) that were housed in terraria for four consecutive breeding seasons. Male mating success increased with male calling rate and chirp duration in both species, suggesting that females preferred males with more elaborate calls. Because calling performance improved with age in D. leucomelas, female poison frogs that prefer males with more elaborate calls in the wild may end up mating with older males that have already proven their ability to survive. Females that mated with good callers obtained higher quality offspring. Eggs fertilized by males with high calling rates and long chirp durations had higher hatching success and produced tadpoles that were more likely to metamorphose into surviving frogs. As a consequence, females that mated with males with high calling performance obtained more surviving offspring per egg, compared to females that mated with poor callers. Collectively, our findings comply with the notion that female poison frogs prefer to mate with good callers because calling performance is a reliable predictor of offspring quality. The possible influence of maternal allocation and reasons for the strong effect size compared to previous studies are discussed.
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| 7. |
- Friberg, Urban, et al.
(författare)
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Assessing the potential for an ongoing arms race within and between the sexes : selection and heritable variation
- 2005
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Ingår i: Evolution. - Lawrence, Kans. : John Wiley & Sons. - 0014-3820 .- 1558-5646. ; 59:7, s. 1540-1551
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Tidskriftsartikel (refereegranskat)abstract
- In promiscuous species, sexual selection generates two opposing male traits: offense (acquiring new mates and supplanting stored sperm) and defense (enforcing fidelity on one's mates and preventing sperm displacement when this fails). Coevolution between these traits requires both additive genetic variation and associated natural selection. Previous work with Drosophila melanogaster found autosomal genetic variation for these traits among inbred lines from a mixture of populations, but only nonheritable genetic variation was found within a single outbred population. These results do not support ongoing antagonistic coevolution between offense and defense, nor between either of these male traits and female reproductive characters. Here we use a new method (hemiclonal analysis) to study genomewide genetic variation in a large outbred laboratory population of D. melanogaster. Hemiclonal analysis estimates the additive genetic variation among random, genomewide haplotypes taken from a large, outbred, locally adapted laboratory population and determines the direction of the selection gradient on this variation. In contrast to earlier studies, we found low but biologically significant heritable variation for defensive and offensive offspring production as well as all their components (P1, fidelity, P2, and remating). Genetic correlations between these traits were substantially different from those reported for inbred lines. A positive genetic correlation was found between defense and offense, demonstrating that some shared genes influence both traits. In addition to this common variation, evidence for unique genetic variation for each trait was also found, supporting an ongoing coevolutionary arms race between defense and offense. Reproductive conflict between males can strongly influence female fitness. Correspondingly, we found genetic variation in both defense and offense that affected female fitness. No evidence was found for intersexual conflict in the context of male defense, but we found substantial intersexual conflict in the context of male offensive sperm competitive ability. These results indicate that conflict between competing males also promotes an associated arms race between the sexes.
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| 8. |
- Bokma, Folmer
(författare)
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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
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Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 62:11, s. 2718-26
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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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| 9. |
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| 10. |
- Engen, Steinar, et al.
(författare)
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Effective size of fluctuating populations with two sexes and overlapping generations
- 2007
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Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 61:8, s. 1873-1885
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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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| 11. |
- Forest, F., et al.
(författare)
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The role of biotic and abiotic factors in evolution of ant dispersal in the milkwort family (Polygalaceae)
- 2007
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Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 61:7, s. 1675-1694
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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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| 12. |
- Fricke, Claudia, et al.
(författare)
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Rapid adaptation to a novel host in a seed beetle (Callosobruchus maculatus) : the role of sexual selection
- 2007
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Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 61:2, s. 440-454
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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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| 13. |
- Hall, David, 1974-, et al.
(författare)
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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
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Ingår i: Evolution. - : Wiley InterScience. - 0014-3820 .- 1558-5646. ; 61, s. 2849-2860
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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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| 14. |
- Hollander, Johan, 1969, et al.
(författare)
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Evolution of adaptation through allometric shifts in a marine snail
- 2006
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Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 60:12, s. 2490-2497
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Tidskriftsartikel (refereegranskat)abstract
- Variation in ontogenetic development among individuals may be a major contributor to morphological variation within species. Evolution of different growth trajectories might, for example, evolve as a response to varying ecological contexts of individuals living in different environments, or by life-stage or gender differences. The intertidal periwinkle Littorina saxatilis is strongly polymorphic in shell shape. We compared ontogenetic trajectories between life stages, local populations, and sexes to understand how different morphological end points are reached during ontogeny and what might cause these differences. Applying landmark-based geometric morphometrics, we captured shell shape variation for four Swedish populations of this species. We also derived a method to visualize ontogenetic trajectories described by the relationship of size to the multivariate shape space. We found that growth trajectories differed between individuals living in different habitats, as well as between sexes and maturity stages. Males living on rocky cliffs grew isometrically throughout life, whereas females from the same habitat switched from isometric growth as juveniles to allometric growth as adults. In contrast, males and females living on boulders grew allometrically as juveniles but changed to isometric growth at sexual maturity. Thus, in this species, ontogenetic growth seems influenced by habitat-associated selection as well as by gender and age-specific selection. These differing selection regimes result in ontogenetic shifts in allometry in three of the four groups examined.
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| 15. |
- 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
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Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 62:9, s. 2279-2296
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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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| 16. |
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| 17. |
- 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
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Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 61:2, s. 324-333
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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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| 18. |
- 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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| 19. |
- Morran, Levi T, et al.
(författare)
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Sexual partners for the stressed : facultative outcrossing in the self-fertilizing nematode Caenorhabditis elegans.
- 2009
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Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 63:6
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Tidskriftsartikel (refereegranskat)abstract
- Sexual reproduction shuffles genetic variation, potentially enhancing the evolutionary response to environmental change. Many asexual organisms respond to stress by generating facultative sexual reproduction, presumably as a means of escaping the trap of low genetic diversity. Self-fertilizing organisms are subject to similar genetic limitations: the consistent loss of genetic diversity within lineages restricts the production of variation through recombination. Selfing organisms may therefore benefit from a similar shift in mating strategy during periods of stress. We determined the effects of environmental stress via starvation and passage through the stress-resistant dauer stage on mating system dynamics of Caenorhabditis elegans, which reproduces predominantly through self-fertilization but is capable of outcrossing in the presence of males. Starvation elevated male frequencies in a strain-specific manner through differential male survival during dauer exposure and increased outcrossing rates after dauer exposure. In the most responsive strain, the mating system changed from predominantly selfing to almost exclusively outcrossing. Like facultative sex in asexual organisms, facultative outcrossing in C. elegans may periodically facilitate adaptation under stress. Such a shift in reproductive strategy should have a major impact on evolutionary change within these populations and may be a previously unrecognized feature of other highly selfing organisms.
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| 20. |
- Rankin, Daniel J., et al.
(författare)
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Sexual dimorphism is associated with population fitness in the seed beetle Callosobruchus maculatus
- 2008
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Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 62:3, s. 622-630
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Tidskriftsartikel (refereegranskat)abstract
- The population consequences of sexual selection remain empirically unexplored. Comparative studies, involving extinction risk, have yielded different results as to the effect of sexual selection on population densities make contrasting predictions. Here, we investigate the relationship between sexual dimorphism (SD) and population productivity in the seed beetle Callosobruchus maculatus, using 13 populations that have evolved in isolation. Geometric morphometric methods and image analysis are employed to form integrative measures of sexual dimorphism, composed of variation in weight, size, body shape, and pigmentation. We found a positive relationship between SD and adult fitness (net adult offspring production) across our study populations, but failed to find any association between SD and juvenile fitness (egg-to-adult survival). Several mechanisms may have contributed to the pattern found, and variance in sexual selection regimes across populations, either in female choice for "good genes" or in the magnitude of direct benefits provided by their mates, would tend to produce the pattern seen. However, our results suggest that evolutionary constraints in the form of intralocus sexual conflict may have been the major generator of the relationship seen between SD and population fitness.
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| 21. |
- Ruxton, Graeme D., et al.
(författare)
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Evolutionary implications of the form of predator generalisation for aposematic signals and mimicry in prey
- 2008
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Ingår i: Evolution: International Journal of Organic Evolution. - : Wiley. - 1558-5646. ; 62:11, s. 2913-2921
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Tidskriftsartikel (refereegranskat)abstract
- Generalization is at the heart of many aspects of behavioral ecology; for foragers it can be seen as an essential feature of learning about potential prey, because natural populations of prey are unlikely to be perfectly homogenous. Aposematic signals are considered to aid predators in learning to avoid a class of defended prey. Predators do this by generalizing between the appearance of prey they have previously sampled and the appearance of prey they subsequently encounter. Mimicry arises when such generalization occurs between individuals of different species. Our aim here is to explore whether the specific shape of the generalization curve can be expected to be important for theoretical predictions relating to the evolution of aposematism and mimicry. We do this by a reanalysis and development of the models provided in two recent papers. We argue that the shape of the generalization curve, in combination with the nature of genetic and phenotypic variation in prey traits, can have evolutionary significance under certain delineated circumstances. We also demonstrate that the process of gradual evolution of Müllerian mimicry proposed by Fisher is particularly efficient in populations with a rich supply of standing genetic variation in mimetic traits.
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| 22. |
- Sandring, Saskia, et al.
(författare)
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Pollinator-mediated selection on floral display and flowering time in the perennial herb Arabidopsis lyrata
- 2009
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Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 63:5, s. 1292-1300
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Tidskriftsartikel (refereegranskat)abstract
- The evolution of floral display and flowering time in animal-pollinated plants is commonly attributed to pollinator-mediated selection. Yet, the causes of selection on flowering phenology and traits contributing to floral display have rarely been tested experimentally in natural populations. We quantified phenotypic selection on morphological and phenological characters in the perennial, outcrossing herb Arabidopsis lyrata in two years using female reproductive success as a proxy of fitness. To determine whether selection on floral display and flowering phenology can be attributed to interactions with pollinators, selection was quantified both for open-pollinated controls and for plants receiving supplemental hand-pollination. We documented directional selection for many flowers, large petals, late start of flowering, and early end of flowering. Seed output was pollen-limited in both years and supplemental hand-pollination reduced the magnitude of selection on number of flowers, and reversed the direction of selection on end of flowering. The results demonstrate that interactions with pollinators may affect the strength of selection on floral display and the direction of selection on phenology of flowering in natural plant populations. They thus support the contention that pollinators can drive the evolution of both floral display and flowering time.
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| 23. |
- Thompson, Stacey Lee, et al.
(författare)
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Three-gene identity coefficients demonstrate that clonal reproduction promotes inbreeding and spatial relatedness in yellow-cedar, Callitropsis nootkatensis
- 2008
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Ingår i: Evolution. - : John Wiley & Sons. - 0014-3820 .- 1558-5646. ; 62:10, s. 2570-2579
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Tidskriftsartikel (refereegranskat)abstract
- Asexual reproduction has the potential to promote population structuring through matings between clones as well as through limited dispersal of related progeny. Here we present an application of three-gene identity coefficients that tests whether clonal reproduction promotes inbreeding and spatial relatedness within populations. With this method, the first two genes are sampled to estimate pairwise relatedness or inbreeding, whereas the third gene is sampled from either a clone or a sexually derived individual. If three-gene coefficients are significantly greater for clones than nonclones, then clonality contributes excessively to genetic structure. First, we describe an estimator of three-gene identity and briefly evaluate its properties. We then use this estimator to test the effect of clonality on the genetic structure within populations of yellow-cedar (Callitropsis nootkatensis) using a molecular marker survey. Five microsatellite loci were genotyped for 485 trees sampled from nine populations. Our three-gene analyses show that clonal ramets promote inbreeding and spatial structure in most populations. Among-population correlations between clonal extent and genetic structure generally support these trends, yet with less statistical significance. Clones appear to contribute to genetic structure through the limited dispersal of offspring from replicated ramets of the same clonal genet, whereas this structure is likely maintained by mating among these relatives.
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| 24. |
- Waldmann, Patrik
(författare)
-
Easy and flexible Bayesian inference of quantitative genetic parameters
- 2009
-
Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 63, s. 1640-1643
-
Tidskriftsartikel (refereegranskat)abstract
- There has been a tremendous advancement of Bayesian methodology in quantitative genetics and evolutionary biology. Still, there are relatively few publications that apply this methodology, probably because the availability of multipurpose and user-friendly software is somewhat limited. It is here described how only a few rows of code of the well-developed and very flexible Bayesian software WinBUGS (Lunn et al. 2000) can be used for inference of the additive polygenic variance and heritabilty in pedigrees of general design. The presented code is illustrated by application to an earlier published dataset of Scots pine.
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| 25. |
- Bokma, F
(författare)
-
Bayesian estimation of speciation and extinction rates from (in)complete phylogenies
- 2008
-
Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 62, s. 2441-2445
-
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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| 26. |
- Dowling, Damian K., et al.
(författare)
-
Temperature-specific outcomes of cytoplasmic-nuclear interactions on egg-to-adult development time in seed beetles
- 2007
-
Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 61:1, s. 194-201
-
Tidskriftsartikel (refereegranskat)abstract
- The integration of the mitochondrial and nuclear genomes coordinates cellular energy production and is fundamental to life among eukaryotes. Therefore, there is potential for strong selection to shape the interactions between the two genomes. Several studies have now demonstrated that epistatic interactions between cytoplasmic and nuclear genes for fitness can occur both at a "within" and "across" population level. Genotype-by-environment interactions are common for traits that are encoded by nuclear genes, but the effects of environmental heterogeneity on traits that are partly encoded by cytoplasmic genes have received little attention despite the fact that there are reasons to believe that phenotypic effects of cytoplasmic genetic variation may often be environment specific. Consequently, the importance of environmental heterogeneity to the outcomes of cyto-nuclear fitness interactions and to the maintenance of mitochondrial polymorphism is unclear. Here, we assess the influence of temperature on cyto-nuclear effects on egg-to-adult development time in seed beetles (Callosobruchus maculatus). We employed an "across-population" design, sourcing beetles from five distinct populations and using backcrossing to create orthogonal combinations of distinct introgression lines, fixed for their cytoplasmic and nuclear lineages. We then assayed development times at two different temperatures and found sizeable cyto-nuclear effects in general, as well as temperature- and block-specific cyto-nuclear effects. These results demonstrate that environmental factors such as temperature do exert selection on cytoplasmic genes by favoring specific cyto-nuclear genetic combinations, and are consistent with the suggestion that complex genotype-by-environment interactions may promote the maintenance of polymorphism in mitochondrial genes.
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| 27. |
- Fritz, Robert S., et al.
(författare)
-
Fitness and genetic architecture of parent and hybrid willows in common gardens
- 2006
-
Ingår i: Evolution. - : Society for the Study of Evolution. - 0014-3820 .- 1558-5646. ; 60:6, s. 1215-1227
-
Tidskriftsartikel (refereegranskat)abstract
- Models of hybrid zone dynamics incorporate different patterns of hybrid fitness relative to parental species fitness. An important but understudied source of variation underlying these fitness differences is the environment. We investigated the performance of two willow species and their F1, F2, and backcross hybrids using a common‐garden experiment with six replicated gardens that differed in soil moisture. Aboveground biomass, catkin production, seed production per catkin, and seed germination rate were significantly different among genetic classes. For aboveground biomass and catkin production, hybrids generally had intermediate or inferior performance compared to parent species. Salix eriocephala had the highest performance for all performance measures, but in two gardens F1 plants had superior or equal performance for aboveground biomass and female catkin production. Salix eriocephala and backcrosses to S. eriocephala had the highest numbers of filled seeds per catkin and the highest estimates of total fitness in all gardens. Measures of filled seeds per catkin and germination rate tend to support the model of endogenous hybrid unfitness, and these two measures had major effects on estimates of total seed production per catkin. We also estimated how the two willow species differ genetically in these fitness measures using line cross analysis. We found a complex genetic architecture underlying the fitness differences between species that involved additive, dominance, and epistatic genetic effects for all fitness measures. The environment was important in the expression of these genetic differences, because the type of epistasis differed among the gardens for aboveground biomass and for female catkin production. These findings suggest that fine‐scale environmental variation can have a significant impact on hybrid fitness in hybrid zones where parents and hybrids are widely interspersed.
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| 28. |
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| 29. |
- Gonzalez-Voyer, Alejandro, et al.
(författare)
-
Sexual selection determines parental care patterns in cichlid fishes
- 2008
-
Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 62:8, s. 2015-2026
-
Tidskriftsartikel (refereegranskat)abstract
- Despite a massive research effort, our understanding of why, in most vertebrates, males compete for mates and females care for offspring remains incomplete. Two alternative hypotheses have been proposed to explain the direction of causality between parental care and sexual selection. Traditionally, sexual selection has been explained as a consequence of relative parental investment, where the sex investing less will compete for the sex investing more. However, a more recent model suggests that parental care patterns result from sexual selection acting on one sex favoring mating competition and lower parental investment. Using species-level comparative analyses on Tanganyikan cichlid fishes we tested these alternative hypotheses employing a proxy of sexual selection based on mating system, sexual dichromatism, and dimorphism data. First, while controlling for female reproductive investment, we found that species with intense sexual selection were associated with female-only care whereas species with moderate sexual selection were associated with biparental care. Second, using contingency analyses, we found that, contrary to the traditional view, evolutionary changes in parental care type are dependent on the intensity of sexual selection. Hence, our results support the hypothesis that sexual selection determines parental care patterns in Tanganyikan cichlid fishes.
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| 30. |
- Maklakov, Alexei A, et al.
(författare)
-
Within-population variation in cytoplasmic genes affects female life span and aging in Drosophila melanogaster
- 2006
-
Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 60:10, s. 2081-2086
-
Tidskriftsartikel (refereegranskat)abstract
- It has been suggested that mitochondrial DNA (mtDNA) may play an important role in aging. Yet, few empirical studies have tested this hypothesis, partly because the degree of sequence polymorphism in mtDNA is assumed to be low. However, low sequence variation may not necessarily translate into low phenotypic variation. Here, we report an experiment that tests whether there is within-population variation in cytoplasmic genes for female longevity and senescence. To achieve this, we randomly selected 25 "mitochondrial founders" from a single, panmictic population of Drosophila melanogaster and used these founders to generate distinct "mt" lines in which we controlled for the nuclear background by successive backcrossing. Potential confounding effects of cytoplasmically transmitted bacteria were eliminated by tetracycline treatment. The mt lines were then assayed for differences in longevity, Gompertz intercept (frailty), and demographic rate of change in mortality with age (rate-of-senescence) in females. We found significant cytoplasmic effects on all three variables. This provides evidence that genetic variation in cytoplasmic genes, presumably mtDNA, contributes to variation in female mortality and aging.
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| 31. |
- Mank, Judith E., et al.
(författare)
-
SEX-LINKAGE OF SEXUALLY ANTAGONISTIC GENES IS PREDICTED BY FEMALE, BUT NOT MALE, EFFECTS IN BIRDS
- 2009
-
Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 63:6, s. 1464-1472
-
Tidskriftsartikel (refereegranskat)abstract
- Evolutionary theory predicts that sexually antagonistic loci will be preferentially sex-linked, and this association can be empirically testes with data on sex-biased gene expression with the assumption that sex-biased gene expression represents the resolution of past sexual antagonism. However, incomplete dosage compensating mechanisms and meiotic sex chromosome inactivation have hampered efforts to connect expression data to theoretical predictions regarding the genomic distribution of sexually antagonistic loci in a variety of animals. Here we use data on the underlying regulatory mechanism that produce expression sex-bias to test the genomic distribution of sexually antagonistic genes in chicken. Using this approach, which is free from problems associated with the lack of dosage compensation in birds, we show that female-detriment genes are significantly overrepresented on the Z chromosome, and female-benefit genes underrepresented. By contrast, male-effect genes show no over-or underrepresentation on the Z chromosome. These data are consistent with a dominant mode of inheritance for sexually antagonistic genes, in which male-benefit coding mutations are more likely to be fixed on the Z due to stronger male-specific selective pressures. After fixation of male-benefit alleles, regulatory changes in females evolve to minimize antagonism by reducing female expression.
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| 32. |
- Wiley, Chris, et al.
(författare)
-
POSTZYGOTIC ISOLATION OVER MULTIPLE GENERATIONS OF HYBRID DESCENDENTS IN A NATURAL HYBRID ZONE : HOW WELL DO SINGLE-GENERATION ESTIMATES REFLECT REPRODUCTIVE ISOLATION?
- 2009
-
Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 63:7, s. 1731-1739
-
Tidskriftsartikel (refereegranskat)abstract
- Understanding speciation depends on an accurate assessment of the reproductive barriers separating newly diverged populations. In several taxonomic groups, prezygotic barriers, especially preferences for conspecific mates, are thought to play the dominant role in speciation. However, the importance of postzygotic barriers (i.e., low fitness of hybrid offspring) may be widely underestimated. In this study, we examined how well the widely used proxy of postzygotic isolation (reproductive output of F1 hybrids) reflects the long-term fitness consequences of hybridization between two closely related species of birds. Using 40 species-specific single nucleotide polymorphism (SNP) markers, we genotyped a mixed population of collared and pied flycatchers (Ficedula albicollis and F. hypoleuca) to identify grand- and great grand-offspring from interspecific crosses to derive an accurate, multigeneration estimate of postzygotic isolation. Two independent estimates of fitness show that hybridization results in 2.4% and 2.7% of the number of descendents typical of conspecific pairing. This postzygotic isolation was considerably stronger than estimates based on F1 hybrids. Our results demonstrate that, in nature, combined selection against hybrids and backcrossed individuals may result in almost complete postzygotic isolation between two comparatively young species. If these findings are general, postzygotic barriers separating hybridizing populations may be much stronger than previously thought.
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| 33. |
- Wright, Dominic, et al.
(författare)
-
The genetic architecture of a female sexual ornament
- 2008
-
Ingår i: Evolution. - Oxford, United Kingdom : Wiley. - 0014-3820 .- 1558-5646. ; 62:1, s. 86-98
-
Tidskriftsartikel (refereegranskat)abstract
- Understanding the evolution of sexual ornaments, and particularly that of female sexual ornaments, is an enduring challenge in evolutionary biology. Key to this challenge are establishing the relationship between ornament expression and female reproductive investment, and determining the genetic basis underpinning such relationship. Advances in genomics provide unprecedented opportunities to study the genetic architecture of sexual ornaments in model species. Here, we present a quantitative trait locus (QTL) analysis of a female sexual ornament, the comb of the fowl, Gallus gallus, using a large-scale intercross between red junglefowl and a domestic line, selected for egg production. First, we demonstrate that female somatic investment in comb reflects female reproductive investment. Despite a trade-off between reproductive and skeletal investment mediated by the mobilization of skeletal minerals for egg production, females with proportionally large combs also had relatively high skeletal investment. Second, we identify a major QTL for bisexual expression of comb mass and several QTL specific to female comb mass. Importantly, QTL for comb mass were nonrandomly clustered with QTL for female reproductive and skeletal investment on chromosomes one and three. Together, these results shed light onto the physiological and genetic architecture of a female ornament.
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| 34. |
- Edelaar, Pim, et al.
(författare)
-
Matching habitat choice causes directed gene flow : A neglected dimension in evolution and ecology
- 2008
-
Ingår i: Evolution. - 0014-3820 .- 1558-5646. ; 62, s. 2462-2472
-
Tidskriftsartikel (refereegranskat)abstract
- Gene flow among populations is typically thought to be antagonistic to population differentiation and local adaptation. However,this assumes that dispersing individuals disperse randomly with respect to their ability to use the environment. Yet dispersingindividuals often sample and compare environments and settle in those environments that best match their phenotype, causingdirected gene flow, which can in fact promote population differentiation and adaptation. We refer to this process as “matchinghabitat choice.” Although this process has been acknowledged by several researchers, no synthesis or perspective on its potentiallywidespread importance exists. Here we synthesize empirical and theoretical studies, and offer a new perspective that matchinghabitat choice can have significant effects on important and controversial topics. We discuss the potential implications of matchinghabitat choice for the degree and rate of local adaptation, the evolution of niche width, adaptive peak shifts, speciation in thepresence of gene flow, and on our view and interpretation of measures of natural selection. Because of its potential importance forsuch a wide range of topics, we call for heightened empirical and theoretical attention for this neglected dimension in evolutionaryand ecological studies.
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| 35. |
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| 36. |
- Heckel, G, et al.
(författare)
-
Genetic structure and colonization processes in European populations of the common vole, Microtus arvalis
- 2005
-
Ingår i: Evolution. - 0014-3820 .- 1558-5646. ; 59:10, s. 2231-2242
-
Tidskriftsartikel (refereegranskat)abstract
- The level of genetic differentiation within and between evolutionary lineages of the common vole (Microtusarvalis) in Europe was examined by analyzing mitochondrial sequences from the control region (mtDNA) and 12nuclear microsatellite loci (nucDNA) for 338 voles from 18 populations. The distribution of evolutionary lineagesand the affinity of populations to lineages were determined with additional sequence data from the mitochondrialcytochrome b gene. Our analyses demonstrated very high levels of differentiation between populations (overall FST:mtDNA 70%; nucDNA 17%). The affinity of populations to evolutionary lineages was strongly reflected in mtDNAbut not in nucDNA variation. Patterns of genetic structure for both markers visualized in synthetic genetic mapssuggest a postglacial range expansion of the species into the Alps, as well as a potentially more ancient colonizationfrom the northeast to the southwest of Europe. This expansion is supported by estimates for the divergence timesbetween evolutionary lineages and within the western European lineage, which predate the last glacial maximum(LGM). Furthermore, all measures of genetic diversity within populations increased significantly with longitude andshowed a trend toward increase with latitude. We conclude that the detected patterns are difficult to explain only byrange expansions from separate LGM refugia close to the Mediterranean. This suggests that someM. arvalis populationspersisted during the LGM in suitable habitat further north and that the gradients in genetic diversity may representtraces of a more ancient colonization of Europe by the species.
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| 37. |
- Hollander, Johan, et al.
(författare)
-
Evolution of adaptation through allometric shifts in a marine snail
- 2006
-
Ingår i: Evolution. - : Wiley. - 1558-5646 .- 0014-3820. ; 60:12, s. 2490-2497
-
Tidskriftsartikel (refereegranskat)abstract
- Variation in ontogenetic development among individuals may be a major contributor to morphological variation within species. Evolution of different growth trajectories might, for example, evolve as a response to varying ecological contexts of individuals living in different environments, or by life-stage or gender differences. The intertidal periwinkle Littorina saxatilis is strongly polymorphic in shell shape. We compared ontogenetic trajectories between life stages, local populations, and sexes to understand how different morphological end points are reached during ontogeny and what might cause these differences. Applying landmark-based geometric morphometrics, we captured shell shape variation for four Swedish populations of this species. We also derived a method to visualize ontogenetic trajectories described by the relationship of size to the multivariate shape space. We found that growth trajectories differed between individuals living in different habitats, as well as between sexes and maturity stages. Males living on rocky cliffs grew isometrically throughout life, whereas females from the same habitat switched from isometric growth as juveniles to allometric growth as adults. In contrast, males and females living on boulders grew allometrically as juveniles but changed to isometric growth at sexual maturity. Thus, in this species, ontogenetic growth seems influenced by habitat-associated selection as well as by gender and age-specific selection. These differing selection regimes result in ontogenetic shifts in allometry in three of the four groups examined.
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| 38. |
- Kaiser, Vera B., et al.
(författare)
-
Nonrandom distribution of genes with sex-biased expression in the chicken genome
- 2006
-
Ingår i: Evolution. - : The Society for the Study of Evolution. - 0014-3820 .- 1558-5646. ; 60:9, s. 1945-1951
-
Tidskriftsartikel (refereegranskat)abstract
- Evolutionary theory predicts that sexually antagonistic genes should show a nonrandom genomic distribution with sex chromosomes usually being enriched for such genes. However, empirical observations from model organisms (Drosophila melanogaster, Caenorhabditis elegans, mammals) on the genomic location of genes with sex-biased expression have provided conflicting data and are not easily explained by a unified framework based on standard models of the evolution of sexually antagonistic genes. Previous studies have been confined to organisms with male heterogamety, meaning that effects related to homo- or heterozygosity of sex chromosomes cannot be separated from effects related to sex-specific characteristics. We therefore studied the genomic distribution of genes with sex-biased expression in the chicken, that is, in an organism with female heterogamety (males ZZ, females ZW). From the abundance of transcripts in expressed sequence tag libraries, we found an underrepresentation of female-specific genes (germ line and somatic tissue) and an overrepresentation of male-specific genes (somatic) on the Z chromosome. This is consistent with theoretical predictions only if mutations beneficial to one sex generally tend to be at least partly dominant (h > 0.5). We also note that sexual selection for a male-biased trait is facilitated by Z-linkage, because sons in organisms with female heterogamety will always inherit a Z chromosome from their fathers.
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| 39. |
- Lankinen, Åsa, et al.
(författare)
-
Sexual conflict over floral receptivity
- 2006
-
Ingår i: Evolution. - : Wiley. - 1558-5646 .- 0014-3820. ; 60:12, s. 2454-2465
-
Tidskriftsartikel (refereegranskat)abstract
- In flowering plants, the onset and duration of female receptivity vary among species. In several species the receptive structures wilt upon pollination. Here we explore the hypothesis that postpollination wilting may be influenced by pollen and serve as a general means to secure paternity of the pollen donor at the expense of female fitness. Taking a game-theoretical approach, we examine the potential for the evolution of a pollen-borne wilting substance, and for the coevolution of a defense strategy by the recipient plant. The model without defense predicts an evolutionarily stable strategy (ESS) for the production of wilting substance. The ESS value is highest when pollinator visiting rates are intermediate and when the probability that pollen from several donors arrives at the same time is low. This finding has general implications in that it shows that male traits to secure paternity also can evolve in species, such as plants, where mating is not strictly sequential. We further model coevolution of the wilting substance with the timing of stigma receptivity. We assume that pollen-receiving plants can reduce the costs induced by toxic pollen by delaying the onset of stigmatic receptivity. The model predicts a joint ESS, but no female counter-adaptation when the wilting substance is highly toxic. This indicates that toxicity affects the probability that a male manipulative trait stays beneficial (i.e., not countered by female defense) over evolutionary time. We discuss parallels to male induced changes in female receptivity known to occur in animals and the role of harm for the evolution of male manipulative adaptations.
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| 40. |
- Maklakov, Alexei A., et al.
(författare)
-
Within-population variation in cytoplasmic genes affects female life span and aging in Drosophila melanogaster
- 2006
-
Ingår i: Evolution. - : The Society for the Study of Evolution. - 0014-3820 .- 1558-5646. ; 60:10, s. 2081-2086
-
Tidskriftsartikel (refereegranskat)abstract
- It has been suggested that mitochondrial DNA (mtDNA) may play an important role in aging. Yet, few empirical studies have tested this hypothesis, partly because the degree of sequence polymorphism in mtDNA is assumed to be low. However, low sequence variation may not necessarily translate into low phenotypic variation. Here, we report an experiment that tests whether there is within-population variation in cytoplasmic genes for female longevity and senescence. To achieve this, we randomly selected 25 "mitochondrial founders" from a single, panmictic population of Drosophila melanogaster and used these founders to generate distinct "mt" lines in which we controlled for the nuclear background by successive backcrossing. Potential confounding effects of cytoplasmically transmitted bacteria were eliminated by tetracycline treatment. The mt lines were then assayed for differences in longevity, Gompertz intercept (frailty), and demographic rate of change in mortality with age (rate-of-senescence) in females. We found significant cytoplasmic effects on all three variables. This provides evidence that genetic variation in cytoplasmic genes, presumably mtDNA, contributes to variation in female mortality and aging.
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| 41. |
- Svensson, Erik, et al.
(författare)
-
Effects of natural and sexual selection on adaptive population divergence and premating isolation in a damselfly.
- 2006
-
Ingår i: Evolution. - : The Society for the Study of Evolution. - 0014-3820 .- 1558-5646. ; 60:6, s. 1242-53
-
Tidskriftsartikel (refereegranskat)abstract
- The relative strength of different types of directional selection has seldom been compared directly in natural populations. A recent meta-analysis of phenotypic selection studies in natural populations suggested that directional sexual selection may be stronger in magnitude than directional natural selection, although this pattern may have partly been confounded by the different time scales over which selection was estimated. Knowledge about the strength of different types of selection is of general interest for understanding how selective forces affect adaptive population divergence and how they may influence speciation. We studied divergent selection on morphology in parapatric, natural damselfly (Calopteryx splendens) populations. Sexual selection was stronger than natural selection measured on the same traits, irrespective of the time scale over which sexual selection was measured. Visualization of the fitness surfaces indicated that population divergence in overall morphology is more strongly influenced by divergent sexual selection rather than natural selection. Courtship success of experimental immigrant males was lower than that of resident males, indicating incipient sexual isolation between these populations. We conclude that current and strong sexual selection promotes adaptive population divergence in this species and that premating sexual isolation may have arisen as a correlated response to divergent sexual selection. Our results highlight the importance of sexual selection, rather than natural selection in the adaptive radiation of odonates, and supports previous suggestions that divergent sexual selection promotes speciation in this group.
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| 42. |
- Vallejo-Marin, M., et al.
(författare)
-
The role of male flowers in andromonoecious species : Energetic costs and siring success in Solanum carolinense L
- 2007
-
Ingår i: Evolution. - 0014-3820 .- 1558-5646. ; 61:2, s. 404-412
-
Tidskriftsartikel (refereegranskat)abstract
- Two non-mutually exclusive hypotheses regarding the benefits of andromonoecy (producing perfect and female-sterile flowers on the same plant) are tested using Solanum carolinense. Results indicate that (1) staminate flowers are cheaper to produce than perfect flowers, even after correcting for their relative position in the inflorescence; (2) the resources saved by producing staminate flowers are not re-allocated to other fitness enhancing functions; and (3)the main morphological characteristic of staminate flowers, pistil reduction, does not increase either pollinator visitation or siring success of open-pollinated plants. These results indicate that neither the resource savings hypothesis nor the increased pollen donation hypothesis explains the evolution and maintenance of andromonoecy in S. carolinense.
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| 43. |
- Gosden, Thomas, et al.
(författare)
-
SPATIAL AND TEMPORAL DYNAMICS IN A SEXUAL SELECTION MOSAIC.
- 2008
-
Ingår i: Evolution. - 1558-5646. ; 62, s. 845-856
-
Tidskriftsartikel (refereegranskat)abstract
- Selective regimes and phenotypic optima could either change smoothly and in a clinal fashion or be spatially organized in a more unpredictable mosaic pattern over the geographic landscape. When natural or sexual selection is driven by intra- or interspecific biotic interactions, fine-grained spatial variation in selective regimes could result in selection mosaics rather than clinal variation in selection. We investigated temporal variation and spatial organization in sexual selection on male body size along an ecological coastal-inland gradient of a polymorphic damselfly Ischnura elegans. Body size increased in a clinal fashion along this gradient: animals were smaller in size at the coast, but became larger in the inland areas. In contrast, the sexual selection regimes on male body size showed evidence of more fine-grained spatial organization with no evidence for a clinal pattern and low spatial autocorrelations between populations. These spatially fine-grained sexual selection regimes varied in sign and magnitude and were driven by a combination of the densities of heritable female color morphs and local female body sizes. We suggest that the spatial organization of the selective regimes can be interpreted as a sexual selection mosaic that is influenced by highly localized density- and frequency-dependent social interactions.
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| 44. |
- Bekkevold, D., et al.
(författare)
-
Environmental correlates of population differentiation in Atlantic herring
- 2005
-
Ingår i: Evolution. - 0014-3820. ; 59:12, s. 2656-2668
-
Tidskriftsartikel (refereegranskat)abstract
- The marine environment is characterized by few physical barriers, and pelagic fishes commonly show high migratory potential and low, albeit in some cases statistically significant, levels of genetic divergence in neutral genetic marker analyses. However, it is not clear whether low levels of differentiation reflect spatially separated populations experiencing gene flow or shallow population histories coupled with limited random genetic drift in large, demographically isolated populations undergoing independent evolutionary processes. Using information for nine microsatellite loci in a total of 1951 fish, we analyzed genetic differentiation among Atlantic herring from eleven spawning locations distributed along a longitudinal gradient from the North Sea to the Western Baltic. Overall genetic differentiation was low (theta = 0.008) but statistically significant. The area is characterized by a dramatic shift in hydrography from the highly saline and temperature stable North Sea to the brackish Baltic Sea, where temperatures show high annual variation. We used two different methods, a novel computational geometric approach and partial Mantel correlation analysis coupled with detailed environmental information from spawning locations to show that patterns of reproductive isolation covaried with salinity differences among spawning locations, independent of their geographical distance. We show that reproductive isolation can be maintained in marine fish populations exhibiting substantial mixing during larval and adult life stages. Analyses incorporating genetic, spatial, and environmental parameters indicated that isolating mechanisms are associated with the specific salinity conditions on spawning locations.
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| 45. |
- Bonneaud, C, et al.
(författare)
-
Major histocompatibility alleles associated with local resistance to malaria in a passerine
- 2006
-
Ingår i: Evolution. - 1558-5646. ; 60:2, s. 383-389
-
Tidskriftsartikel (refereegranskat)abstract
- Malaria parasites are a major cause of human mortality in tropical countries and a potential threat for wildlife, as witnessed by the malaria-induced extinction of naive Hawaiian avifauna. Identifying resistance mechanisms is therefore crucial both for human health and wildlife conservation. Patterns of malaria resistance are known to be highly polygenic in both humans and mice, with marked contributions attributed to major histocompatibility (Mhc) genes. Here we show that specific Mhc variants are linked to both increased resistance and susceptibility to malaria infection in a wild passerine species, the house sparrow (Passer domesticus). In addition, links between host immunogenctics and resistance to malaria involved population-specific alleles, suggesting local adaptation in this host-parasite interaction. This is the first evidence for a population-specific genetic control of resistance to malaria in a wild species.
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| 46. |
- Broggi, J, et al.
(författare)
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Local adaptation to winter conditions in a passerine spreading north: A common-garden approach
- 2005
-
Ingår i: Evolution. - 1558-5646. ; 59:7, s. 1600-1603
-
Tidskriftsartikel (refereegranskat)abstract
- Sedentary passerine birds living in temperate and boreal regions need a high metabolic capacity for thermogenesis to survive winter conditions. As a consequence of the increased thermogenic capacity, basal energetic demands rise at a time when resources and time to acquire them decrease. In a previous study, great tits (Parus major) from two localities in Fennoscandia with contrasting winter conditions differed in their metabolic response to ambient temperature. To investigate the physiological basis underlying interpopulation differences we performed a common-garden experiment to test whether these differences were genetically based. We found basal metabolic rate to be higher in birds originating from transferred eggs from the southern population compared to the ones from the northern population, contrary to the relationship among birds living in their region of origin. Despite previous evidence suggesting that gene flow prevents local adaptation at the northern range limits of a species expanding northward, we found that great tits differ in their reaction norm to winter conditions according to the population of origin.
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| 47. |
- Jörgensen, Tove, et al.
(författare)
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Comparative analyses of population structure in two subspecies of Nigella degenii: Evidence for diversifying selection on pollen-color dimorphisms
- 2006
-
Ingår i: Evolution. - 1558-5646. ; 60:3, s. 518-528
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Tidskriftsartikel (refereegranskat)abstract
- Flower color can be a major determinant of plant fitness, not only because of preferential visitation by pollinators but also because of pleiotropic relationships between the expression of floral pigments and biochemically related compounds that influence vegetative performance variables. Different environments may therefore favor different pigmentation phenotypes. We examined whether spatially varying selection has played a major role in shaping large-scale patterns of differentiation in two subspecies of Nigella degenii (Ranunculaceae), with particular emphasis on pollen color. The two subspecies appear to have been genetically isolated for substantial periods of time and, therefore, provide a "replicated test" for the effect of natural selection. Estimates of population structure based on a suite of floral and vegetative characters were compared with the corresponding data for amplified fragment length polymorphism (AFLP) markers, which were assumed to be selectively neutral. We found low levels of genetic structure within the subspecies using both the AFLP markers (F-ST <= 0.05) and quantitative characters (Q(ST) <= 0.15), with no statistically significant differences between the two measures. There is, therefore, no evidence of diversifying selection being important in structuring variation in quantitative characters within each of the two subspecies. In contrast, estimates of differentiation in pollen color (F-ST <= 0.10) significantly exceeded the neutral expectations (estimated from AFLP data), Suggesting that local adaptation has played a key role in the evolution of this monogenic character.
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| 48. |
- Leimar, Olof, et al.
(författare)
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Evolution of phenotypic clusters through competition and local adaptation along an environmental gradient.
- 2008
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Ingår i: Evolution. - : Wiley. - 0014-3820. ; 62:4, s. 807-22
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Tidskriftsartikel (refereegranskat)abstract
- We have analyzed the evolution of a quantitative trait in populations that are spatially extended along an environmental gradient, with gene flow between nearby locations. In the absence of competition, there is stabilizing selection toward a locally best-adapted trait that changes gradually along the gradient. According to traditional ideas, gradual spatial variation in environmental conditions is expected to lead to gradual variation in the evolved trait. A contrasting possibility is that the trait distribution instead breaks up into discrete clusters. Doebeli and Dieckmann (2003) argued that competition acting locally in trait space and geographical space can promote such clustering. We have investigated this possibility using deterministic population dynamics for asexual populations, analyzing our model numerically and through an analytical approximation. We examined how the evolution of clusters is affected by the shape of competition kernels, by the presence of Allee effects, and by the strength of gene flow along the gradient. For certain parameter ranges clustering was a robust outcome, and for other ranges there was no clustering. Our analysis shows that the shape of competition kernels is important for clustering: the sign structure of the Fourier transform of a competition kernel determines whether the kernel promotes clustering. Also, we found that Allee effects promote clustering, whereas gene flow can have a counteracting influence. In line with earlier findings, we could demonstrate that phenotypic clustering was favored by gradients of intermediate slope.
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| 49. |
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| 50. |
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