Rapid adaptive divergence between ecotypes of an aquatic isopod inferred from FST–QST analysis

Eroukhmanoff, Fabrice; Hargeby, Anders; Svensson, Erik I.

doi:10.1111/j.1365-294x.2009.04408.x

Cited by 28 publications

(60 citation statements)

References 55 publications

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“…Recently, it has been argued that comparisons of population divergence between putatively adaptive traits (often referred to as "Q ST ") and neutral population divergence (F ST ), should utilize the whole neutral F ST -distribution to see if the adaptive traits fall within this distribution, before the null hypothesis of genetic drift can be safely rejected [16,44]. We follow these recommendations and visualized the entire neutral F ST -distribution and its relationship to our adaptive trait (color morph divergence).…”

Section: Methodsmentioning

confidence: 99%

“…One possible approach might be to study whether the population distribution of a heritable phenotypic character differs from the neutral expectation or not [7,15,16] . Neutral genetic markers can be used to estimate the effective population sizes (N e ), and from such data, the expected probability of fixation of neutral and selected alleles can be calculated.…”

Section: Introductionmentioning

confidence: 99%

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Island biology and morphological divergence of the Skyros wall lizard Podarcis gaigeae: a combined role for local selection and genetic drift on color morph frequency divergence?

et al. 2010

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BackgroundPatterns of spatial variation in discrete phenotypic traits can be used to draw inferences about the adaptive significance of traits and evolutionary processes, especially when compared to patterns of neutral genetic variation. Population divergence in adaptive traits such as color morphs can be influenced by both local ecology and stochastic factors such as genetic drift or founder events. Here, we use quantitative color measurements of males and females of Skyros wall lizard, Podarcis gaigeae, to demonstrate that this species is polymorphic with respect to throat color, and the morphs form discrete phenotypic clusters with limited overlap between categories. We use divergence in throat color morph frequencies and compare that to neutral genetic variation to infer the evolutionary processes acting on islet- and mainland populations.ResultsGeographically close islet- and mainland populations of the Skyros wall lizard exhibit strong divergence in throat color morph frequencies. Population variation in throat color morph frequencies between islets was higher than that between mainland populations, and the effective population sizes on the islets were small (Ne:s < 100). Population divergence (FST) for throat color morph frequencies fell within the neutral FST-distribution estimated from microsatellite markers, and genetic drift could thus not be rejected as an explanation for the pattern. Moreover, for both comparisons among mainland-mainland population pairs and between mainland-islet population pairs, morph frequency divergence was significantly correlated with neutral divergence, further pointing to some role for genetic drift in divergence also at the phenotypic level of throat color morphs.ConclusionsGenetic drift could not be rejected as an explanation for the pattern of population divergence in morph frequencies. In spite of an expected stabilising selection, throat color frequencies diverged in the islet populations. These results suggest that there is an interaction between selection and genetic drift causing divergence even at a phenotypic level in these small, subdivided populations.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Island biology and morphological divergence of the Skyros wall lizard Podarcis gaigeae: a combined role for local selection and genetic drift on color morph frequency divergence?

et al. 2010

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“…We do not have estimates of heritabilities or among-population genetic variances, which are usually a prerequisite for this type of indirect inference, namely F ST -Q ST comparisons (Merilä and Crnokrak, 2001;Eroukhmanoff et al, 2009;reviewed by Whitlock 2008). However, it is possible, with appropriate caution, to instead use phenotypic variance components corrected for the missing quantitative genetic estimates in such analyses (see for example, Saether et al, 2007).…”

Section: Phenotypic Traits Under Selection and The Role Of Environmenmentioning

confidence: 99%

Local adaptation within a hybrid species

Eroukhmanoff

Bailey

et al. 2013

Heredity

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Ecological divergence among populations may be strongly influenced by their genetic background. For instance, genetic admixture through introgressive hybridization or hybrid speciation is likely to affect the genetic variation and evolvability of phenotypic traits. We studied geographic variation in two beak dimensions and three other phenotypic traits of the Italian sparrow (Passer italiae), a young hybrid species formed through interbreeding between house sparrows (P. domesticus) and Spanish sparrows (P. hispaniolensis). We found that beak morphology was strongly influenced by precipitation regimes and that it appeared to be the target of divergent selection within Italian sparrows. Interestingly, however, the degree of parental genetic contribution in the hybrid species had no effect on phenotypic beak variation. Moreover, beak height divergence may mediate genetic differentiation between populations, consistent with isolation-by-adaptation within this hybrid species. The study illustrates how hybrid species may be relatively unconstrained by their admixed genetic background, allowing them to adapt rapidly to environmental variation.

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“…Indirect inferences of selection, based on comparisons of F st /Q st divergence [cf. 36], on these four ecotype populations have furthermore shown that differentiation between the ecotype populations is far greater than if driven by neutral processes like genetic drift alone [37] The main cause for ecotype divergence is suggested to be habitat-differences in predation regimes, either the number or types of predators, or a combination [31].…”

Section: Introductionmentioning

confidence: 99%

Phenotypic Plasticity in Response to the Social Environment: Effects of Density and Sex Ratio on Mating Behaviour Following Ecotype Divergence

2010

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The ability to express phenotypically plastic responses to environmental cues might be adaptive in changing environments. We studied phenotypic plasticity in mating behaviour as a response to population density and adult sex ratio in a freshwater isopod (Asellus aquaticus). A. aquaticus has recently diverged into two distinct ecotypes, inhabiting different lake habitats (reed Phragmites australis and stonewort Chara tomentosa, respectively). In field surveys, we found that these habitats differ markedly in isopod population densities and adult sex ratios. These spatially and temporally demographic differences are likely to affect mating behaviour. We performed behavioural experiments using animals from both the ancestral ecotype (“reed” isopods) and from the novel ecotype (“stonewort” isopods) population. We found that neither ecotype adjusted their behaviour in response to population density. However, the reed ecotype had a higher intrinsic mating propensity across densities. In contrast to the effects of density, we found ecotype differences in plasticity in response to sex ratio. The stonewort ecotype show pronounced phenotypic plasticity in mating propensity to adult sex ratio, whereas the reed ecotype showed a more canalised behaviour with respect to this demographic factor. We suggest that the lower overall mating propensity and the phenotypic plasticity in response to sex ratio have evolved in the novel stonewort ecotype following invasion of the novel habitat. Plasticity in mating behaviour may in turn have effects on the direction and intensity of sexual selection in the stonewort habitat, which may fuel further ecotype divergence.

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Rapid adaptive divergence between ecotypes of an aquatic isopod inferred from F_ST–Q_ST analysis

Cited by 28 publications

References 55 publications

Island biology and morphological divergence of the Skyros wall lizard Podarcis gaigeae: a combined role for local selection and genetic drift on color morph frequency divergence?

Island biology and morphological divergence of the Skyros wall lizard Podarcis gaigeae: a combined role for local selection and genetic drift on color morph frequency divergence?

Local adaptation within a hybrid species

Phenotypic Plasticity in Response to the Social Environment: Effects of Density and Sex Ratio on Mating Behaviour Following Ecotype Divergence

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