Department of Animal and Plant Sciences, The University of Sheffield, Sheffield, South Yorkshire S10 2TN, UNITED KINGDOM.
Models for the evolution of species' traits and speciation rates usually ignore ecology: most comparative analyses of evolution are ecologically neutral and ignore ecological mechanisms such as competition and limiting similarity. However, such processes can impact profoundly on the distribution of traits across a group of species if they are ecologically similar (e.g. as in adaptive radiations). Here, two new models are introduced to explicitly include the effects of lineage-lineage interactions, one generating trait evolution and the other addressing lineage diversification. The new model for trait evolution is fitted to a wide range of existing animal datasets, using a simulation approach. Evidence was found of clade-wide character displacement patterns in some adaptive radiations, including Darwin’s finches; however, these patterns are not prevalent across animal clades as a whole. Three types of diversification model are also compared here, including the novel interaction-based diversification model. This new model links trait space densities to diversification rates, supressing diversification among closely packed species. Although these models have a similar conceptual basis, in terms of the accumulation of filled niches, they produce quite different evolutionary histories. The implications of ecological interactions between species are discussed, both for data interpretation and for future modelling approaches.