Assessing latitudinal gradients in speciation rates and biodiversity at the global scale

Andrew P. Allen*, James F. Gillooly

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

149 Citations (Scopus)


The mechanisms responsible for latitudinal biodiversity gradients have fascinated and perplexed biologists since the time of Darwin. Ecological theory has yielded two general classes of mechanisms to account for variation in biodiversity: dispersal-assembly mechanisms that invoke differences in stochastic rates of speciation, extinction and dispersal; and niche-assembly mechanisms that invoke species differences, species interactions and environmental heterogeneity. Distinguishing between these two classes of mechanisms requires explicit consideration of macroevolutionary dynamics. Here, we assess the importance of dispersal-assembly mechanisms in the origin and maintenance of biodiversity using fossil data that encompass 30 million years of macroevolution for three distinct groups of ocean plankton: foraminifera, nannoplankton and radiolaria. Applying new methods of analysis to these fossil data, we show here for the first time that latitudinal biodiversity gradients exhibit strong positive correlations with speciation rates even after explicitly controlling for variation in sampling effort and for increases in habitat area towards the equator. These findings provide compelling evidence that geographical variation in macroevolutionary dynamics is a primary determinant of contemporary biodiversity gradients, as predicted by dispersal-assembly theory.

Original languageEnglish
Pages (from-to)947-954
Number of pages8
JournalEcology Letters
Issue number8
Publication statusPublished - Aug 2006
Externally publishedYes


  • Latitudinal gradient
  • Metabolic theory of ecology
  • Neutral theory of biodiversity
  • Niche conservatism
  • Speciation rate
  • Species-area relationship


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