The Shape and Temporal Dynamics of Phylogenetic Trees Arising from Geographic Speciation

Alex L. Pigot, Albert B. Phillimore, Ian P. F. Owens, C. David L. Orme

Research output: Contribution to journalArticlepeer-review

Abstract

Phylogenetic trees often depart from the expectations of stochastic models, exhibiting imbalance in diversification among lineages and slowdowns in the rate of lineage accumulation through time. Such departures have led to a widespread perception that ecological differences among species or adaptation and subsequent niche filling are required to explain patterns of diversification. However, a key element missing from models of diversification is the geographical context of speciation and extinction. In this study, we develop a spatially explicit model of geographic range evolution and cladogenesis, where speciation arises via vicariance or peripatry, and explore the effects of these processes on patterns of diversification. We compare the results with those observed in 41 reconstructed avian trees. Our model shows that nonconstant rates of speciation and extinction are emergent properties of the apportioning of geographic ranges that accompanies speciation. The dynamics of diversification exhibit wide variation, depending on the mode of speciation, tendency for range expansion, and rate of range evolution. By varying these parameters, the model is able to capture many, but not all, of the features exhibited by birth-death trees and extant bird clades. Under scenarios with relatively stable geographic ranges, strong slowdowns in diversification rates are produced, with faster rates of range dynamics leading to constant or accelerating rates of apparent diversification. A peripatric model of speciation with stable ranges also generates highly unbalanced trees typical of bird phylogenies but fails to produce realistic range size distributions among the extant species. Results most similar to those of a birth-death process are reached under a peripatric speciation scenario with highly volatile range dynamics. Taken together, our results demonstrate that considering the geographical context of speciation and extinction provides a more conservative null model of diversification and offers a very different perspective on the phylogenetic patterns expected in the absence of ecology.

Original languageEnglish
Pages (from-to)660-673
Number of pages14
JournalSystematic biology
Volume59
Issue number6
Early online date15 Oct 2010
DOIs
Publication statusPublished - 31 Dec 2010

Keywords

  • Geographic speciation
  • null models
  • phylogenetic trees
  • range evolution
  • range size
  • slowdowns
  • species diversification
  • tree imbalance
  • SPECIES RICHNESS
  • EVOLUTIONARY PROCESS
  • CLADE DIVERSIFICATION
  • MOLECULAR PHYLOGENIES
  • EXTINCTION RATES
  • PASSERINE BIRDS
  • RANGE
  • MODELS
  • PATTERNS
  • DISTRIBUTIONS

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