Proceedings of the Royal Society B: Biological Sciences
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Evidence for determinism in species diversification and contingency in phenotypic evolution during adaptive radiation

Frank T. Burbrink

Frank T. Burbrink

Department of Biology, The College of Staten Island, The City University of New York, 2800 Victory Boulevard, Staten Island, NY 10314, USA

Department of Biology, The Graduate School and University Center, The City University of New York, 365 Fifth Avenue, New York, NY 10016, USA

[email protected]

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Xin Chen

Xin Chen

Department of Biology, The College of Staten Island, The City University of New York, 2800 Victory Boulevard, Staten Island, NY 10314, USA

Department of Biology, The Graduate School and University Center, The City University of New York, 365 Fifth Avenue, New York, NY 10016, USA

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Edward A. Myers

Edward A. Myers

Department of Biology, The College of Staten Island, The City University of New York, 2800 Victory Boulevard, Staten Island, NY 10314, USA

Department of Biology, The Graduate School and University Center, The City University of New York, 365 Fifth Avenue, New York, NY 10016, USA

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Matthew C. Brandley

Matthew C. Brandley

School of Biological Sciences, University of Sydney, New South Wales 2006, Australia

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R. Alexander Pyron

R. Alexander Pyron

Department of Biological Sciences, The George Washington University, 2023 G Street NW, Washington DC 20052, USA

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Published:https://doi.org/10.1098/rspb.2012.1669

    Adaptive radiation (AR) theory predicts that groups sharing the same source of ecological opportunity (EO) will experience deterministic species diversification and morphological evolution. Thus, deterministic ecological and morphological evolution should be correlated with deterministic patterns in the tempo and mode of speciation for groups in similar habitats and time periods. We test this hypothesis using well-sampled phylogenies of four squamate groups that colonized the New World (NW) in the Late Oligocene. We use both standard and coalescent models to assess species diversification, as well as likelihood models to examine morphological evolution. All squamate groups show similar early pulses of speciation, as well as diversity-dependent ecological limits on clade size at a continental scale. In contrast, processes of morphological evolution are not easily predictable and do not show similar pulses of early and rapid change. Patterns of morphological and species diversification thus appear uncoupled across these groups. This indicates that the processes that drive diversification and disparification are not mechanistically linked, even among similar groups of taxa experiencing the same sources of EO. It also suggests that processes of phenotypic diversification cannot be predicted solely from the existence of an AR or knowledge of the process of diversification.

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