Evolutionary and ecological causes of the latitudinal diversity gradient in hylid frogs: Treefrog trees unearth the roots of high tropical diversity

John J. Wiens, Catherine H. Graham, Daniel S. Moen, Sarah A. Smith, Tod W. Reeder

Research output: Contribution to journalReview article

308 Scopus citations

Abstract

Why are there more species in the tropics than in temperate regions? In recent years, this long-standing question has been addressed primarily by seeking environmental correlates of diversity. But to understand the ultimate causes of diversity patterns, we must also examine the evolutionary and biogeographic processes that directly change species numbers (i.e., speciation, extinction, and dispersal). With this perspective, we dissect the latitudinal diversity gradient in hylid frogs. We reconstruct a phylogeny for 124 hylid species, estimate divergence times and diversification rates for major clades, reconstruct biogeographic changes, and use ecological niche modeling to identify climatic variables that potentially limit dispersal. We find that hylids originated in tropical South America and spread to temperate regions only recently (leaving limited time for speciation). There is a strong relationship between the species richness of each region and when that region was colonized but not between the latitudinal positions of clades and their rates of diversification. Temperature seasonality seemingly limits dispersal of many tropical clades into temperate regions and shows significant phylogenetic conservatism. Overall, our study illustrates how two general principles (niche conservatism and the time-for-speciation effect) may help explain the latitudinal diversity gradient as well as many other diversity patterns across taxa and regions.

Original languageEnglish (US)
Pages (from-to)579-596
Number of pages18
JournalAmerican Naturalist
Volume168
Issue number5
DOIs
StatePublished - Nov 1 2006
Externally publishedYes

Keywords

  • Amphibians
  • Biogeography
  • Latitudinal gradient
  • Niche conservatism
  • Phylogeny
  • Species richness

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics

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