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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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Correlation of variations between head shape and trophic traits revealed by PLS analysis.Individuals were pooled for local populations, with bars showing standard deviations. The coefficients of each trophic trait for “trophic traits” axis were the following: ED, 0.498; ML, 0.339; JL, 0.373; MW, 0.129; HW, –0.694. Thin-plate spline grids represent the shape of individuals of plus and minus extremes (all magnified two times). Sample codes correspond to those in Figure 1A and Table 1.
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pone-0017430-g004: Correlation of variations between head shape and trophic traits revealed by PLS analysis.Individuals were pooled for local populations, with bars showing standard deviations. The coefficients of each trophic trait for “trophic traits” axis were the following: ED, 0.498; ML, 0.339; JL, 0.373; MW, 0.129; HW, –0.694. Thin-plate spline grids represent the shape of individuals of plus and minus extremes (all magnified two times). Sample codes correspond to those in Figure 1A and Table 1.

Mentions: PLS yielded five dimensions of covariation between the two blocks of variable sets (i.e., head shape variables and trophic traits), of which only the first dimension was significantly greater than expected by chance (p<0.05). The first dimension accounted for 79.8% of the covariance. The correlation between the blocks was 0.52, which was also significant (p<0.01; Figure 4). On both the “head shape” and “trophic traits” axes, local populations were distributed so that the difference in habitat type served as a threshold. Based on thin-plate spline grids, the shape divergence axis represented a shape change for a short-headed (minus extreme) to a long-headed individual (plus extreme). We also estimated the coefficient of each trophic trait against the “trophic traits” axis: ED, 0.498; ML, 0.339; JL, 0.373; JW, 0.129; HW, –0.694. These results suggested that long-headed individuals, which were found at high frequencies in the rocky zone, have larger eyes, a longer mouth with a larger jaw, and a horizontally compressed head.


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)

Correlation of variations between head shape and trophic traits revealed by PLS analysis.Individuals were pooled for local populations, with bars showing standard deviations. The coefficients of each trophic trait for “trophic traits” axis were the following: ED, 0.498; ML, 0.339; JL, 0.373; MW, 0.129; HW, –0.694. Thin-plate spline grids represent the shape of individuals of plus and minus extremes (all magnified two times). Sample codes correspond to those in Figure 1A and Table 1.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0017430-g004: Correlation of variations between head shape and trophic traits revealed by PLS analysis.Individuals were pooled for local populations, with bars showing standard deviations. The coefficients of each trophic trait for “trophic traits” axis were the following: ED, 0.498; ML, 0.339; JL, 0.373; MW, 0.129; HW, –0.694. Thin-plate spline grids represent the shape of individuals of plus and minus extremes (all magnified two times). Sample codes correspond to those in Figure 1A and Table 1.
Mentions: PLS yielded five dimensions of covariation between the two blocks of variable sets (i.e., head shape variables and trophic traits), of which only the first dimension was significantly greater than expected by chance (p<0.05). The first dimension accounted for 79.8% of the covariance. The correlation between the blocks was 0.52, which was also significant (p<0.01; Figure 4). On both the “head shape” and “trophic traits” axes, local populations were distributed so that the difference in habitat type served as a threshold. Based on thin-plate spline grids, the shape divergence axis represented a shape change for a short-headed (minus extreme) to a long-headed individual (plus extreme). We also estimated the coefficient of each trophic trait against the “trophic traits” axis: ED, 0.498; ML, 0.339; JL, 0.373; JW, 0.129; HW, –0.694. These results suggested that long-headed individuals, which were found at high frequencies in the rocky zone, have larger eyes, a longer mouth with a larger jaw, and a horizontally compressed head.

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
Related in: MedlinePlus