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An asymmetry in niche conservatism contributes to the latitudinal species diversity gradient in New World vertebrates

Authors

  • Brian Tilston Smith,

    Corresponding author
    • Museum of Natural Science, Louisiana State University, Baton Rouge, LA, USA
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  • Robert W. Bryson Jr.,

    1. Marjorie Barrick Museum of Natural History, University of Nevada Las Vegas, Las Vegas, NV, USA
    Current affiliation:
    1. Department of Biology and Burke Museum, Box 351800, University of Washington, Seattle, Washington, USA
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  • Derek D. Houston,

    1. Department of Biology, Brigham Young University, Provo, UT, USA
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  • John Klicka

    1. Marjorie Barrick Museum of Natural History, University of Nevada Las Vegas, Las Vegas, NV, USA
    Current affiliation:
    1. Department of Biology and Burke Museum, Box 351800, University of Washington, Seattle, Washington, USA
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Correspondence: E-mail: briantilstonsmith@gmail.com

Abstract

The Tropical Niche Conservatism hypothesis is a leading explanation for why biodiversity increases towards the equator. The model suggests that most lineages have tropical origins, with few dispersing into temperate regions. However, biotas are comprised of lineages with differing geographical origins, thus it is unclear whether lineages that originated on different continents will exhibit similar patterns of niche conservatism. Here, we summarised biogeographical patterns of New World vertebrates and compared species diversity patterns between families that originated in North and South America. Overall, families with southern origins exhibit niche conservatism with many lineages restricted to the Neotropics, whereas many northern-origin families are distributed across the Neotropics and the Nearctic. Consequently, northern lineages have contributed to high tropical biodiversity, but southern lineages have contributed relatively little to temperate biodiversity in North America. The asymmetry in niche conservatism between northern and southern lineages is an important contributor to the biodiversity gradient.

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