UBC Theses and Dissertations
Exploring the relationship between trait evolution and the generation of species diversity Magnuson-Ford, Karen
Macroevolutionary questions, such as "why do some lineages diversify faster than others?", are often studied by investigating key traits related to species’ ecology and life-history. Many traits have been hypothesized to affect rates of diversification and often it is these traits that are used to address another macroevolutionary question: "do traits evolve gradually over time or in punctuated bursts during speciation?" Using phylogenetic data and species’ present-day trait information, I present a novel approach to assess the mode of character change while accounting for state-dependent speciation and extinction. The model, Binary-State Speciation and Extinction - node enhanced state shift (BiSSE-ness), estimates both the rate of change occurring along lineages and the probability of change occurring during speciation, while simultaneously estimating the speciation and extinction rates for each character state. Using simulations, I found BiSSE-ness is able to distinguish along-lineage and speciational change and precisely estimate the parameters associated with character change and diversification rates. I applied BiSSE-ness to an empirical primate data set examining five traits related to ecology, behaviour, and reproduction. I provide evidence that changes in primate habitat type may be associated with speciation, whereas changes in social behaviour and mating system occur mainly along lineages. The BiSSE-ness model is flexible in that it may be used to address questions regarding species diversification, regardless of whether the trait changes in a manner that is proportional to time or to the number of speciation events. However, in cases where the trait is linked to the speciation process itself, such as niche-related traits, BiSSE-ness provides a suitable framework in which to simultaneously address questions regarding species’ diversification and character change.
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