Abstract
The incorporation of ecological processes into models of trait evolution is important for understanding past drivers of evolutionary change. Species interactions have long been thought to be key drivers of trait evolution. However, models for comparative data that account for interactions between species are lacking. One of the challenges is that such models are intractable and difficult to express analytically. Here we present phylogenetic models of trait evolution that include interspecific competition among chosen species. Competition is modeled as a tendency of sympatric species to evolve toward difference from one another, producing trait overdispersion and high phylogenetic signal. The model predicts elevated trait variance across species and a slowdown in evolutionary rate both across the clade and within each branch. The model also predicts a reduction in correlation between otherwise correlated traits. We use an approximate Bayesian computation approach to estimate model parameters. We find reasonable power to detect competition in sufficiently large (20+ species) trees compared with Brownian trait evolution and with Ornstein-Uhlenbeck and early burst models. We apply the model to examine the evolution of bill morphology of Darwin's finches and find evidence that competition affects the evolution of bill length.
Highlights
There is an increasing drive to combine evolutionary and ecological perspectives in order to fully capture the longterm dynamics of ecological communities (Johnson and Stinchcombe 2007; Cavender-Bares et al 2009; Schoener 2011; Pennell and Harmon 2013; Hadfield et al 2014; Price et al 2014; Pigot and Etienne 2015)
We find reasonable power to detect competition in sufficiently large (201 species) trees compared with Brownian trait evolution and with OrnsteinUhlenbeck and early burst models
We introduce a new model for the evolution of interacting species within phylogenetic data
Summary
There is an increasing drive to combine evolutionary and ecological perspectives in order to fully capture the longterm dynamics of ecological communities (Johnson and Stinchcombe 2007; Cavender-Bares et al 2009; Schoener 2011; Pennell and Harmon 2013; Hadfield et al 2014; Price et al 2014; Pigot and Etienne 2015). The second line of evidence for competitive effects makes use of a phylogeny to measure the distribution of species trait values relative to a null model (Webb et al 2002; Freckleton and Harvey 2006; Vamosi et al 2009). This is especially useful for adaptive radiations, where typically several similar species are confined to the same geographical area. Distributions that are more even than expected by chance (Webb et al 2002; Dayan and Simberloff 2005; Davies et al 2012) are taken as evidence that past competition caused species to seek unique ecological niches
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