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Morphological divergence driven by predation environment within and between species of Brachyrhaphis fishes.

Ingley SJ, Billman EJ, Belk MC, Johnson JB - PLoS ONE (2014)

Bottom Line: Natural selection often results in profound differences in body shape among populations from divergent selective environments.Interestingly, at both levels of divergence we found that early in ontogenetic development, females differed in shape between predation environments; however, as females matured, their body shapes converged on a similar phenotype, likely due to the constraints of pregnancy.Finally, we found that body shape varies with body size in a similar way, regardless of predation environment, in each lineage.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Brigham Young University, Provo, Utah, United States of America.

ABSTRACT
Natural selection often results in profound differences in body shape among populations from divergent selective environments. Predation is a well-studied driver of divergence, with predators having a strong effect on the evolution of prey body shape, especially for traits related to escape behavior. Comparative studies, both at the population level and between species, show that the presence or absence of predators can alter prey morphology. Although this pattern is well documented in various species or population pairs, few studies have tested for similar patterns of body shape evolution at multiple stages of divergence within a taxonomic group. Here, we examine morphological divergence associated with predation environment in the livebearing fish genus Brachyrhaphis. We compare differences in body shape between populations of B. rhabdophora from different predation environments to differences in body shape between B. roseni and B. terrabensis (sister species) from predator and predator free habitats, respectively. We found that in each lineage, shape differed between predation environments, consistent with the hypothesis that locomotor function is optimized for either steady swimming (predator free) or escape behavior (predator). Although differences in body shape were greatest between B. roseni and B. terrabensis, we found that much of the total morphological diversification between these species had already been achieved within B. rhabdophora (29% in females and 47% in males). Interestingly, at both levels of divergence we found that early in ontogenetic development, females differed in shape between predation environments; however, as females matured, their body shapes converged on a similar phenotype, likely due to the constraints of pregnancy. Finally, we found that body shape varies with body size in a similar way, regardless of predation environment, in each lineage. Our findings are important because they provide evidence that the same source of selection can drive similar phenotypic divergence independently at multiple divergence levels.

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Morphological Divergence in Male Brachyrhaphis.Visualization of morphological divergence with centroid size in male Brachyrhaphis roseni (a), B. terrabensis (b), and B. rhabdophora from predator (c) and predator free (d) environments. Thin-plate spline transformations depict the end points of the centroid size axis (i.e. the smallest and largest individuals). Shaded regions are drawn to aid in interpretation. Note the shortening and deepening of the head region and the reduction in the caudle peduncle region in large males. Deformations are scaled to 3X to assist interpretation of the shape differences.
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pone-0090274-g004: Morphological Divergence in Male Brachyrhaphis.Visualization of morphological divergence with centroid size in male Brachyrhaphis roseni (a), B. terrabensis (b), and B. rhabdophora from predator (c) and predator free (d) environments. Thin-plate spline transformations depict the end points of the centroid size axis (i.e. the smallest and largest individuals). Shaded regions are drawn to aid in interpretation. Note the shortening and deepening of the head region and the reduction in the caudle peduncle region in large males. Deformations are scaled to 3X to assist interpretation of the shape differences.

Mentions: To determine how shape varies across size classes (hypothesis 4) in females (due to changes associated with pregnancy) and males (due to potential differences in mating strategies and ontogenetic effects), we generated thin-plate splines in tpsRegr [81] using centroid size and superimposed landmark coordinates to visualize shape variation along the centroid size axis in females (Fig. 3) and males (Fig. 4) of both species. We found that females showed a shift in morphology from small to large that was characterized by an increase in abdomen size and a decrease in caudal peduncle area. Adult males showed a shift in morphology from small to large that was characterized by a shortening and deepening of the head region and a reduction in the caudle peduncle region.


Morphological divergence driven by predation environment within and between species of Brachyrhaphis fishes.

Ingley SJ, Billman EJ, Belk MC, Johnson JB - PLoS ONE (2014)

Morphological Divergence in Male Brachyrhaphis.Visualization of morphological divergence with centroid size in male Brachyrhaphis roseni (a), B. terrabensis (b), and B. rhabdophora from predator (c) and predator free (d) environments. Thin-plate spline transformations depict the end points of the centroid size axis (i.e. the smallest and largest individuals). Shaded regions are drawn to aid in interpretation. Note the shortening and deepening of the head region and the reduction in the caudle peduncle region in large males. Deformations are scaled to 3X to assist interpretation of the shape differences.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3936007&req=5

pone-0090274-g004: Morphological Divergence in Male Brachyrhaphis.Visualization of morphological divergence with centroid size in male Brachyrhaphis roseni (a), B. terrabensis (b), and B. rhabdophora from predator (c) and predator free (d) environments. Thin-plate spline transformations depict the end points of the centroid size axis (i.e. the smallest and largest individuals). Shaded regions are drawn to aid in interpretation. Note the shortening and deepening of the head region and the reduction in the caudle peduncle region in large males. Deformations are scaled to 3X to assist interpretation of the shape differences.
Mentions: To determine how shape varies across size classes (hypothesis 4) in females (due to changes associated with pregnancy) and males (due to potential differences in mating strategies and ontogenetic effects), we generated thin-plate splines in tpsRegr [81] using centroid size and superimposed landmark coordinates to visualize shape variation along the centroid size axis in females (Fig. 3) and males (Fig. 4) of both species. We found that females showed a shift in morphology from small to large that was characterized by an increase in abdomen size and a decrease in caudal peduncle area. Adult males showed a shift in morphology from small to large that was characterized by a shortening and deepening of the head region and a reduction in the caudle peduncle region.

Bottom Line: Natural selection often results in profound differences in body shape among populations from divergent selective environments.Interestingly, at both levels of divergence we found that early in ontogenetic development, females differed in shape between predation environments; however, as females matured, their body shapes converged on a similar phenotype, likely due to the constraints of pregnancy.Finally, we found that body shape varies with body size in a similar way, regardless of predation environment, in each lineage.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Brigham Young University, Provo, Utah, United States of America.

ABSTRACT
Natural selection often results in profound differences in body shape among populations from divergent selective environments. Predation is a well-studied driver of divergence, with predators having a strong effect on the evolution of prey body shape, especially for traits related to escape behavior. Comparative studies, both at the population level and between species, show that the presence or absence of predators can alter prey morphology. Although this pattern is well documented in various species or population pairs, few studies have tested for similar patterns of body shape evolution at multiple stages of divergence within a taxonomic group. Here, we examine morphological divergence associated with predation environment in the livebearing fish genus Brachyrhaphis. We compare differences in body shape between populations of B. rhabdophora from different predation environments to differences in body shape between B. roseni and B. terrabensis (sister species) from predator and predator free habitats, respectively. We found that in each lineage, shape differed between predation environments, consistent with the hypothesis that locomotor function is optimized for either steady swimming (predator free) or escape behavior (predator). Although differences in body shape were greatest between B. roseni and B. terrabensis, we found that much of the total morphological diversification between these species had already been achieved within B. rhabdophora (29% in females and 47% in males). Interestingly, at both levels of divergence we found that early in ontogenetic development, females differed in shape between predation environments; however, as females matured, their body shapes converged on a similar phenotype, likely due to the constraints of pregnancy. Finally, we found that body shape varies with body size in a similar way, regardless of predation environment, in each lineage. Our findings are important because they provide evidence that the same source of selection can drive similar phenotypic divergence independently at multiple divergence levels.

Show MeSH
Related in: MedlinePlus