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Gradient evolution of body colouration in surface- and cave-dwelling Poecilia mexicana and the role of phenotype-assortative female mate choice.

Bierbach D, Penshorn M, Hamfler S, Herbert DB, Appel J, Meyer P, Slattery P, Charaf S, Wolf R, Völker J, Berger EA, Dröge J, Wolf K, Riesch R, Arias-Rodriguez L, Indy JR, Plath M - Biomed Res Int (2013)

Bottom Line: Ecological speciation assumes reproductive isolation to be the product of ecologically based divergent selection.Beside natural selection, sexual selection via phenotype-assortative mating is thought to promote reproductive isolation.Hence, divergent selection on body colouration indeed translates into phenotype-assortative mating in the surface ecotype, by selecting against potential migrant males.

View Article: PubMed Central - PubMed

Affiliation: Evolutionary Ecology Group, Johann-Wolfgang-Goethe University of Frankfurt, Max-von-Laue-Street 13, 60438 Frankfurt am Main, Germany ; Department of Biology and Ecology of Fishes, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 310, 12587 Berlin, Germany.

ABSTRACT
Ecological speciation assumes reproductive isolation to be the product of ecologically based divergent selection. Beside natural selection, sexual selection via phenotype-assortative mating is thought to promote reproductive isolation. Using the neotropical fish Poecilia mexicana from a system that has been described to undergo incipient ecological speciation in adjacent, but ecologically divergent habitats characterized by the presence or absence of toxic H2S and darkness in cave habitats, we demonstrate a gradual change in male body colouration along the gradient of light/darkness, including a reduction of ornaments that are under both inter- and intrasexual selection in surface populations. In dichotomous choice tests using video-animated stimuli, we found surface females to prefer males from their own population over the cave phenotype. However, female cave fish, observed on site via infrared techniques, preferred to associate with surface males rather than size-matched cave males, likely reflecting the female preference for better-nourished (in this case: surface) males. Hence, divergent selection on body colouration indeed translates into phenotype-assortative mating in the surface ecotype, by selecting against potential migrant males. Female cave fish, by contrast, do not have a preference for the resident male phenotype, identifying natural selection against migrants imposed by the cave environment as the major driver of the observed reproductive isolation.

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Related in: MedlinePlus

Principal components analysis (PCA). Shown are mean (±SE) principal component scores extracted from PCA on L*a*b* values of all 10 regions on the male body surface for each population. The strongest axis loadings (see main text) are further indicated. Arroyo Bonita (AB, green square), El Azufre (EA, red square), Cueva del Azufre chamber II (CA-II, white square), chamber V (CA-V, grey square), and chamber X (CA-X, black square).
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fig4: Principal components analysis (PCA). Shown are mean (±SE) principal component scores extracted from PCA on L*a*b* values of all 10 regions on the male body surface for each population. The strongest axis loadings (see main text) are further indicated. Arroyo Bonita (AB, green square), El Azufre (EA, red square), Cueva del Azufre chamber II (CA-II, white square), chamber V (CA-V, grey square), and chamber X (CA-X, black square).

Mentions: As a qualitative overview, we present mean values (±SE) for L*, a*, and b* of the different spots for all populations examined (Figure 3). However, our central question was whether the examined populations differ overall in body colouration and which colour values of the particular spots contributed most to possible differences. We thus conducted PCA (principle component analysis) to condense our data. L*a*b*-values from all 10 spots were included, and PC axes with eigenvalues above 1 were extracted. Resulting axis loadings were Varimax-rotated for better interpretation. For presentation purpose, mean (±SE) PC scores with strongest axis loadings (values that were within a range of 0.10 starting at the highest value) are shown at the respective axes (Figure 4). PC scores were then used as dependent variables in MANCOVA with “population” as fixed factor and body length of the photographed fish (“SL”) as covariate, including the interaction term “population × SL”. Post hoc ANCOVAs for each extracted PC axis separately (but otherwise identical model structure) were applied to disentangle which PC axes contributed to a possible population effect in the MANCOVA. Interaction terms were removed if nonsignificant. Significant effects of “SL” were post hoc analysed using Pearson correlations while in case of significant interaction terms standardized residuals were analysed instead. All analyses were conducted using SPSS 13 and all data are presented as mean ± S.E. Prior to all analyses, data were checked to meet requirements of normal distribution and homoscedasticity.


Gradient evolution of body colouration in surface- and cave-dwelling Poecilia mexicana and the role of phenotype-assortative female mate choice.

Bierbach D, Penshorn M, Hamfler S, Herbert DB, Appel J, Meyer P, Slattery P, Charaf S, Wolf R, Völker J, Berger EA, Dröge J, Wolf K, Riesch R, Arias-Rodriguez L, Indy JR, Plath M - Biomed Res Int (2013)

Principal components analysis (PCA). Shown are mean (±SE) principal component scores extracted from PCA on L*a*b* values of all 10 regions on the male body surface for each population. The strongest axis loadings (see main text) are further indicated. Arroyo Bonita (AB, green square), El Azufre (EA, red square), Cueva del Azufre chamber II (CA-II, white square), chamber V (CA-V, grey square), and chamber X (CA-X, black square).
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3794506&req=5

fig4: Principal components analysis (PCA). Shown are mean (±SE) principal component scores extracted from PCA on L*a*b* values of all 10 regions on the male body surface for each population. The strongest axis loadings (see main text) are further indicated. Arroyo Bonita (AB, green square), El Azufre (EA, red square), Cueva del Azufre chamber II (CA-II, white square), chamber V (CA-V, grey square), and chamber X (CA-X, black square).
Mentions: As a qualitative overview, we present mean values (±SE) for L*, a*, and b* of the different spots for all populations examined (Figure 3). However, our central question was whether the examined populations differ overall in body colouration and which colour values of the particular spots contributed most to possible differences. We thus conducted PCA (principle component analysis) to condense our data. L*a*b*-values from all 10 spots were included, and PC axes with eigenvalues above 1 were extracted. Resulting axis loadings were Varimax-rotated for better interpretation. For presentation purpose, mean (±SE) PC scores with strongest axis loadings (values that were within a range of 0.10 starting at the highest value) are shown at the respective axes (Figure 4). PC scores were then used as dependent variables in MANCOVA with “population” as fixed factor and body length of the photographed fish (“SL”) as covariate, including the interaction term “population × SL”. Post hoc ANCOVAs for each extracted PC axis separately (but otherwise identical model structure) were applied to disentangle which PC axes contributed to a possible population effect in the MANCOVA. Interaction terms were removed if nonsignificant. Significant effects of “SL” were post hoc analysed using Pearson correlations while in case of significant interaction terms standardized residuals were analysed instead. All analyses were conducted using SPSS 13 and all data are presented as mean ± S.E. Prior to all analyses, data were checked to meet requirements of normal distribution and homoscedasticity.

Bottom Line: Ecological speciation assumes reproductive isolation to be the product of ecologically based divergent selection.Beside natural selection, sexual selection via phenotype-assortative mating is thought to promote reproductive isolation.Hence, divergent selection on body colouration indeed translates into phenotype-assortative mating in the surface ecotype, by selecting against potential migrant males.

View Article: PubMed Central - PubMed

Affiliation: Evolutionary Ecology Group, Johann-Wolfgang-Goethe University of Frankfurt, Max-von-Laue-Street 13, 60438 Frankfurt am Main, Germany ; Department of Biology and Ecology of Fishes, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 310, 12587 Berlin, Germany.

ABSTRACT
Ecological speciation assumes reproductive isolation to be the product of ecologically based divergent selection. Beside natural selection, sexual selection via phenotype-assortative mating is thought to promote reproductive isolation. Using the neotropical fish Poecilia mexicana from a system that has been described to undergo incipient ecological speciation in adjacent, but ecologically divergent habitats characterized by the presence or absence of toxic H2S and darkness in cave habitats, we demonstrate a gradual change in male body colouration along the gradient of light/darkness, including a reduction of ornaments that are under both inter- and intrasexual selection in surface populations. In dichotomous choice tests using video-animated stimuli, we found surface females to prefer males from their own population over the cave phenotype. However, female cave fish, observed on site via infrared techniques, preferred to associate with surface males rather than size-matched cave males, likely reflecting the female preference for better-nourished (in this case: surface) males. Hence, divergent selection on body colouration indeed translates into phenotype-assortative mating in the surface ecotype, by selecting against potential migrant males. Female cave fish, by contrast, do not have a preference for the resident male phenotype, identifying natural selection against migrants imposed by the cave environment as the major driver of the observed reproductive isolation.

Show MeSH
Related in: MedlinePlus