The tempo and mode of evolution: Body sizes of island mammals

Pasquale Raia*, Shai Meiri

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The tempo and mode of body size evolution on islands are believed to be well known. It is thought that body size evolves relatively quickly on islands toward the mammalian modal value, thus generating extreme cases of size evolution and the island rule. Here, we tested both theories in a phylogenetically explicit context, by using two different species-level mammalian phylogenetic hypotheses limited to sister clades dichotomizing into an exclusively insular and an exclusively mainland daughter nodes. Taken as a whole, mammals were found to show a largely punctuational mode of size evolution. We found that, accounting for this, and regardless of the phylogeny used, size evolution on islands is no faster than on the continents. We compared different selection regimes using a set of Ornstein-Uhlenbeck models to examine the effects of insularity of the mode of evolution. The models strongly supported clade-specific selection regimes. Under this regime, however, an evolutionary model allowing insular species to evolve differently from their mainland relatives performs worse than a model that ignores insularity as a factor. Thus, insular taxa do not experience statistically different selection from their mainland relatives.

Original languageEnglish
Pages (from-to)1927-1934
Number of pages8
JournalEvolution; international journal of organic evolution
Issue number7
StatePublished - Jul 2011


  • Body size
  • Islands
  • Ornstein-Uhlenbeck models
  • Punctuated equilibrium
  • Rates of phenotypic evolution
  • θ statistic
  • κ statistic


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