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A novel resource polymorphism in fish, driven by differential bottom environments: an example from an ancient lake in Japan.

Komiya T, Fujita S, Watanabe K - PLoS ONE (2011)

Bottom Line: Genetic analyses based on mitochondrial and nuclear microsatellite DNA data revealed no clear genetic differentiation among local populations within/between the gudgeon species.Although the morphogenetic factors that contribute to morphological divergence remain unclear, our results suggest that the gudgeon populations in Lake Biwa show a state of resource polymorphism associated with differences in the bottom environment.This is a novel example of resource polymorphism in fish within an Asian ancient lake, emphasizing the importance and generality of feeding adaptation as an evolutionary mechanism that generates morphological diversification.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Science, Kyoto University, Kyoto, Japan. komiya@terra.zool.kyoto-u.ac.jp

ABSTRACT
Divergent natural selection rooted in differential resource use can generate and maintain intraspecific eco-morphological divergence (i.e., resource polymorphism), ultimately leading to population splitting and speciation. Differing bottom environments create lake habitats with different benthos communities, which may cause selection in benthivorous fishes. Here, we document the nature of eco-morphological and genetic divergence among local populations of the Japanese gudgeon Sarcocheilichthys (Cyprinidae), which inhabits contrasting habitats in the littoral zones (rocky vs. pebbly habitats) in Lake Biwa, a representative ancient lake in East Asia. Eco-morphological analyses revealed that Sarcocheilichthys variegatus microoculus from rocky and pebbly zones differed in morphology and diet, and that populations from rocky environments had longer heads and deeper bodies, which are expected to be advantageous for capturing cryptic and/or attached prey in structurally complex, rocky habitats. Sarcocheilichthys biwaensis, a rock-dwelling specialist, exhibited similar morphologies to the sympatric congener, S. v. microoculus, except for body/fin coloration. Genetic analyses based on mitochondrial and nuclear microsatellite DNA data revealed no clear genetic differentiation among local populations within/between the gudgeon species. Although the morphogenetic factors that contribute to morphological divergence remain unclear, our results suggest that the gudgeon populations in Lake Biwa show a state of resource polymorphism associated with differences in the bottom environment. This is a novel example of resource polymorphism in fish within an Asian ancient lake, emphasizing the importance and generality of feeding adaptation as an evolutionary mechanism that generates morphological diversification.

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Landmarks used in morphometric analyses (A, B) and trophic traits (A).Trophic traits are eye diameter (ED), mouth length (ML), jaw length (JL), mouth width (MW), and head width (HW).
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pone-0017430-g002: Landmarks used in morphometric analyses (A, B) and trophic traits (A).Trophic traits are eye diameter (ED), mouth length (ML), jaw length (JL), mouth width (MW), and head width (HW).

Mentions: We hypothesized that natural selection might favor morphological divergence of multiple features (body units). We therefore focused on the relationships between locomotion behavior and body units that are often highlighted for successful feeding (e.g., the relationship between searching ability and body shape), as well as the relationship between prey-capture ability and head shape. To quantify shape variation among individuals, we conducted landmark-based geometric morphometric analyses (GM; [33], [34]). GM is a critical tool for analyzing morphometric shape variation. In contrast to the traditional linear measuring approach, GM retains the geometry among landmarks throughout the analysis, which makes it possible to generate graphical representations of shape variation. We first digitized the biologically homologous landmarks of each individual (Figure 2) on images using software TPSDIG2 version 2.12 [35]. For the alignment of the individuals, we used TPSREGR version 1.37 [36] to perform generalized procrustes superimposition [33], [37], which scales, translates, and rotates the landmarks to line them up as closely as possible. These superimposed landmarks were used to compute affine and non-affine shape components (i.e., uniform components and partial warps) using TPSREGR. We used these components as shape variables, drawing the morphology of each individual in the subsequent statistical analyses. The resulting shape axes were visualized as thin-plate spline transformation grids (constructed using TPSREGR), which exhibit lucid graphic display based on deformation grids [33].


A novel resource polymorphism in fish, driven by differential bottom environments: an example from an ancient lake in Japan.

Komiya T, Fujita S, Watanabe K - PLoS ONE (2011)

Landmarks used in morphometric analyses (A, B) and trophic traits (A).Trophic traits are eye diameter (ED), mouth length (ML), jaw length (JL), mouth width (MW), and head width (HW).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3046152&req=5

pone-0017430-g002: Landmarks used in morphometric analyses (A, B) and trophic traits (A).Trophic traits are eye diameter (ED), mouth length (ML), jaw length (JL), mouth width (MW), and head width (HW).
Mentions: We hypothesized that natural selection might favor morphological divergence of multiple features (body units). We therefore focused on the relationships between locomotion behavior and body units that are often highlighted for successful feeding (e.g., the relationship between searching ability and body shape), as well as the relationship between prey-capture ability and head shape. To quantify shape variation among individuals, we conducted landmark-based geometric morphometric analyses (GM; [33], [34]). GM is a critical tool for analyzing morphometric shape variation. In contrast to the traditional linear measuring approach, GM retains the geometry among landmarks throughout the analysis, which makes it possible to generate graphical representations of shape variation. We first digitized the biologically homologous landmarks of each individual (Figure 2) on images using software TPSDIG2 version 2.12 [35]. For the alignment of the individuals, we used TPSREGR version 1.37 [36] to perform generalized procrustes superimposition [33], [37], which scales, translates, and rotates the landmarks to line them up as closely as possible. These superimposed landmarks were used to compute affine and non-affine shape components (i.e., uniform components and partial warps) using TPSREGR. We used these components as shape variables, drawing the morphology of each individual in the subsequent statistical analyses. The resulting shape axes were visualized as thin-plate spline transformation grids (constructed using TPSREGR), which exhibit lucid graphic display based on deformation grids [33].

Bottom Line: Genetic analyses based on mitochondrial and nuclear microsatellite DNA data revealed no clear genetic differentiation among local populations within/between the gudgeon species.Although the morphogenetic factors that contribute to morphological divergence remain unclear, our results suggest that the gudgeon populations in Lake Biwa show a state of resource polymorphism associated with differences in the bottom environment.This is a novel example of resource polymorphism in fish within an Asian ancient lake, emphasizing the importance and generality of feeding adaptation as an evolutionary mechanism that generates morphological diversification.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Science, Kyoto University, Kyoto, Japan. komiya@terra.zool.kyoto-u.ac.jp

ABSTRACT
Divergent natural selection rooted in differential resource use can generate and maintain intraspecific eco-morphological divergence (i.e., resource polymorphism), ultimately leading to population splitting and speciation. Differing bottom environments create lake habitats with different benthos communities, which may cause selection in benthivorous fishes. Here, we document the nature of eco-morphological and genetic divergence among local populations of the Japanese gudgeon Sarcocheilichthys (Cyprinidae), which inhabits contrasting habitats in the littoral zones (rocky vs. pebbly habitats) in Lake Biwa, a representative ancient lake in East Asia. Eco-morphological analyses revealed that Sarcocheilichthys variegatus microoculus from rocky and pebbly zones differed in morphology and diet, and that populations from rocky environments had longer heads and deeper bodies, which are expected to be advantageous for capturing cryptic and/or attached prey in structurally complex, rocky habitats. Sarcocheilichthys biwaensis, a rock-dwelling specialist, exhibited similar morphologies to the sympatric congener, S. v. microoculus, except for body/fin coloration. Genetic analyses based on mitochondrial and nuclear microsatellite DNA data revealed no clear genetic differentiation among local populations within/between the gudgeon species. Although the morphogenetic factors that contribute to morphological divergence remain unclear, our results suggest that the gudgeon populations in Lake Biwa show a state of resource polymorphism associated with differences in the bottom environment. This is a novel example of resource polymorphism in fish within an Asian ancient lake, emphasizing the importance and generality of feeding adaptation as an evolutionary mechanism that generates morphological diversification.

Show MeSH