Ecomorphological disparity in an adaptive radiation: opercular bone shape and stable isotopes in Antarctic icefishes |
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Authors: | Laura A B Wilson Marco Colombo Reinhold Hanel Walter Salzburger Marcelo R Sánchez‐Villagra |
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Affiliation: | 1. Pal?ontologisches Institute und Museum, , CH 8006 Zürich, Switzerland;2. School of Biological, Earth and Environmental Sciences, University of New South Wales, , Kensington, NSW, 2052 Australia;3. Zoological Institute, University of Basel, , CH 4051 Basel, Switzerland;4. Institute of Fisheries Ecology, Johann Heinrich von Thünen‐Institute, Federal Research Institute for Rural Areas, Forestry and Fisheries, , 22767 Hamburg, Germany |
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Abstract: | To assess how ecological and morphological disparity is interrelated in the adaptive radiation of Antarctic notothenioid fish we used patterns of opercle bone evolution as a model to quantify shape disparity, phylogenetic patterns of shape evolution, and ecological correlates in the form of stable isotope values. Using a sample of 25 species including representatives from four major notothenioid clades, we show that opercle shape disparity is higher in the modern fauna than would be expected under the neutral evolution Brownian motion model. Phylogenetic comparative methods indicate that opercle shape data best fit a model of directional selection (Ornstein–Uhlenbeck) and are least supported by the “early burst” model of adaptive radiation. The main evolutionary axis of opercle shape change reflects movement from a broad and more symmetrically tapered opercle to one that narrows along the distal margin, but with only slight shape change on the proximal margin. We find a trend in opercle shape change along the benthic–pelagic axis, underlining the importance of this axis for diversification in the notothenioid radiation. A major impetus for the study of adaptive radiations is to uncover generalized patterns among different groups, and the evolutionary patterns in opercle shape among notothenioids are similar to those found among other adaptive radiations (three‐spined sticklebacks) promoting the utility of this approach for assessing ecomorphological interactions on a broad scale. |
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Keywords: | Craniofacial bone ecology geometric morphometrics phylogeny stable isotopes |
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