| 1. |
- Ceplitis, Helene
(författare)
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Evolutionary dynamics of mitochondrial plasmids in natural populations of Silene vulgaris
- 2002
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Ingår i: Evolution. - : Wiley. - 1558-5646 .- 0014-3820. ; 56:8, s. 1592-1598
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Tidskriftsartikel (refereegranskat)abstract
- Although plasmid-like mitochondrial DNA molecules have been investigated in a number of cultivated plant species, knowledge about their occurrence and behavior in natural plant populations is scarce. In the bladder campion, Silene vulgaris, a common weed of northern Europe, mt-plasmids of three different sizes were detected in a survey of S. vulgaris populations in southern Sweden. Two of the three plasmids usually occurred together within individual plants and showed large variation in frequency between populations. From F-ST-estimates of plasmids, mitochondrial markers, and nuclear markers it was concluded that the plasmids are predominantly maternally inherited in their natural habitat, as observed in greenhouse experiments. The association between mt-plasmids and mitochondrial haplotype was strong, but not complete, in the natural material. These results indicate that the mt-plasmids of S. vulgaris have evolved toward almost strict maternal inheritance.
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| 2. |
- Ceplitis, Helene, et al.
(författare)
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Transmission rates and phenotypic effects of mitochondrial plasmids and cytotypes in Silene vulgaris
- 2002
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Ingår i: Evolution. - : Wiley. - 1558-5646 .- 0014-3820. ; 56:8, s. 1586-1591
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the transmission properties and the phenotypic effects of two mitochondrial plasmids in a population of the bladder campion, Silene vulgaris. In reciprocal crosses between plasmid-free and plasmid-carrying plants, no cases of paternal transmission or loss during maternal transmission were recorded. Neither was any transmission via pollen observed when plasmid-carrying plants of S, vulgaris were used to pollinate plasmid-free plants of the closely related species Silene uniflora. The phenotypic effects of the plasmids were investigated by comparing germination rate, early growth properties, and the gender of plants grown from seeds with and without plasmids. A significant association between plasmid status, on the one hand, and germination propensity and offspring gender, on the other, was found. However, because all plants carrying plasmids in the experiment shared the same cytoplasmic background, the exact contribution of the plasmid to the phenotypic variation could not be determined. Taken together, our experiments show that in S. vulgaris the mt-plasmids are not currently involved in any strong genetic conflict, but that they evolve in close association with their mitochondrial host.
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| 3. |
- Eroukhmanoff, Fabrice, et al.
(författare)
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THE ROLE OF DIFFERENT REPRODUCTIVE BARRIERS DURING PHENOTYPIC DIVERGENCE OF ISOPOD ECOTYPES
- 2011
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Ingår i: Evolution. - : Wiley-Blackwell. - 0014-3820 .- 1558-5646. ; 65:9, s. 2631-2640
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Tidskriftsartikel (refereegranskat)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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| 4. |
- Hargeby, Anders, et al.
(författare)
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Habitat-specific pigmentation in a freshwater isopod : Adaptive evolution over a small spatiotemporal scale
- 2004
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Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 58:1, s. 81-94
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Tidskriftsartikel (refereegranskat)abstract
- Pigmentation in the freshwater isopod Asellus aquaticus (Crustacea) differed between habitats in two Swedish lakes. In both lakes, isopods had lighter pigmentation in stands of submerged vegetation, consisting of stoneworts (Chara spp.), than in nearby stands of reed (Phragmites australis). Experimental crossings of light and dark isopods in a common environment showed that pigmentation had a genetic basis and that genetic variance was additive. Environmental effects of diet or chromatophore adjustment to the background had minor influence on pigmentation, as shown by laboratory rearing of isopods on stonewort or reed substrates, as well as analyses of stable isotope ratios for isopods collected in the field. In both study lakes, the average phenotype became lighter with time (across generations) in recently established stonewort stands. Taken together, these results indicate that altered phenotype pigmentation result from evolutionary responses to local differences in natural selection. Based on the assumption of two generations per year, the evolutionary rate of change in pigmentationwas 0.08 standard deviations per generation (haldanes) over 20 generations in one lake and 0.22 haldanes over two generations in the other lake. This genetic change occurred during an episode of population growth in a novel habitat, a situation known to promote adaptive evolution. In addition, stonewort stands constitute large and persistent patches, characteristics that tend to preserve local adaptations produced by natural selection. Results from studies on selective forces behind the adaptivedivergence suggest that selective predation from visually oriented predators is a possible selective agent. We found no indications of phenotype-specificmovements between habitats. Mating within stonewort stands was random with respect to pigmentation, but on a whole-lake scale it is likely that mating is assortative, as a result of local differences in phenotype distribution.
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| 5. |
- Holmér, Jennie, et al.
(författare)
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The origin of polymorphic crypsis in a heterogeneous environment
- 2010
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Ingår i: Evolution. - : Wiley. - 1558-5646 .- 0014-3820. ; 64, s. 1386-1394
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Tidskriftsartikel (refereegranskat)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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| 6. |
- Jenkins, Tania, et al.
(författare)
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Migratory behavior of birds affects their coevolutionary relationship with blood parasites
- 2012
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Ingår i: Evolution. - : Wiley. - 1558-5646 .- 0014-3820. ; 66:3, s. 740-751
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Tidskriftsartikel (refereegranskat)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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| 7. |
- 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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| 8. |
- 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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| 9. |
- Lassance, Jean-Marc, et al.
(författare)
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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
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Ingår i: Evolution. - : Wiley. - 1558-5646 .- 0014-3820. ; 65:6, s. 1583-1593
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Tidskriftsartikel (refereegranskat)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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| 10. |
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