Theory predicts a rapid transition from niche-structured to neutral biodiversity patterns across a speciation-rate gradient

Ryan A. Chisholm, Stephen Wilson Pacala

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


A central challenge in community ecology is to predict patterns of biodiversity with mechanistic models. The neutral model of biodiversity is a simple model that appears to provide parsimonious and accurate predictions of biodiversity patterns in some ecosystems, even though it ignores processes such as species interactions and niche structure. In a recent paper, we used analytical techniques to reveal why the mean predictions of the neutral model are robust to niche structure in high diversity but not low-diversity ecosystems. In the present paper, we explore this phenomenon further by generating stochastic simulated data from a spatially implicit hybrid niche-neutral model across different speciation rates. We compare the resulting patterns of species richness and abundance with the patterns expected from a pure neutral and a pure niche model. As the speciation rate in the hybrid model increases, we observe a surprisingly rapid transition from an ecosystem in which diversity is almost entirely governed by niche structure to one in which diversity is statistically indistinguishable from that of the neutral model. Because the transition is rapid, one prediction of our abstract model is that high-diversity ecosystems such as tropical forests can be approximated by one simple model-the neutral model-whereas low-diversity ecosystems such as temperate forests can be approximated by another simple model-the niche model. Ecosystems that require the hybrid model are predicted to be rare, occurring only over a narrow range of speciation rates.

Original languageEnglish (US)
Pages (from-to)195-200
Number of pages6
JournalTheoretical Ecology
Issue number2
StatePublished - May 2011

All Science Journal Classification (ASJC) codes

  • Ecology
  • Ecological Modeling


  • Biodiversity
  • Community ecology
  • Emergent pattern
  • Neutral theory
  • Niche model
  • Speciation rate


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