Abstract
ABSTRACTA myriad of factors have been shown to influence the morphology of freshwater fish. However, studies that parse out where variation is coming from (e.g. body size, sex, and habitat) as well as what potential these changes have to influence function (e.g. swimming performance) are understudied. Therefore, the objectives of this study were to describe morphological variation of Bluegill Lepomis macrochirus across the Grand Lake St Mary's watershed area (northwest OH, USA) and test for covariation of morphology with size, sex, and habitat as well as to assess swimming performance to discern whether any differences in habitat (and morphology) correspond with functional aspects related to critical swimming velocity. Geometric morphometric methods were used to assess shape variation among individuals and general linear models were used to test for covariation of morphology with size, sex, and habitat. Analyses indicated that body size was the strongest driver of morphological variation followed by sex, habitat, and interactions – indicating the presence of allometry, sexual dimorphism, and the potential for habitat induced plasticity. In general, more robust morphologies tended to correspond with larger individuals, males, and/or individuals from lentic habitats. Swimming performance trials supported functional differences as individuals from lotic habitats demonstrated significantly higher Ucrit swimming performance values (∼+20%) than lentic individuals. Broader applications of these findings can link to evolutionary ecology, management, and conservation.
Highlights
The relationship between organismal morphology and environment is a long standing topic of interest among ecologists and has been steadily gaining interest since the first ecomorphology studies began to relate form, function, and environment (Delacour & Mayr 1945; Verheyen 1953; Delacour 1959)
The primary objectives of this study were to (1) describe variation in Bluegill body morphology across the Grand Lake St Mary’s (GLSM’s) watershed area by testing for morphological covariation with body size, sex, and local habitat using novel morphometric methodologies as well as (2) to review and establish potential functional mechanisms related to morphological variation that could be tied to diet, fecundity, and/or swimming performance using a combination of literature reviews and laboratory testing
relative warp analysis (RWA) retained 12 axes which explained a total of 95% of the morphological variability, weighed most heavily along the first 3 which explained 65% of morphological variation of Bluegill in the GLSM watershed area
Summary
The relationship between organismal morphology and environment is a long standing topic of interest among ecologists and has been steadily gaining interest since the first ecomorphology studies began to relate form, function, and environment (Delacour & Mayr 1945; Verheyen 1953; Delacour 1959). Ecomorphology has helped facilitate understanding of what can potentially drive body shape and niche and has established templates for the study of morphological relationships with resource use, life history, and evolution. The application of ecomorphology can provide valuable insight into ontogeny, phylogeny, and evolution. Despite the obvious utility of ecomorphology and its growing literature base – there is still much room for improving our understanding of the various taxonomic groups and clades of North American fishes.
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