James Boyko , Brian O'Meara, Jeremy Beaulieu

Whether modeling the evolution of a discrete or continuous character, the focal trait of interest does not evolve in isolation and require comparative methods that model multivariate evolution. Progress along these lines has involved modeling multivariate evolution of the same class of character and there are fewer options when jointly modeling traits when one character is discrete and the other is continuous. Here we develop such a framework to explicitly estimate the joint likelihood for discrete and continuous characters. Specifically, our model combines the probability of observing the continuous character under a generalized OU process with the probability of the discrete character under a hidden Markov model, linked by a shared underlying regime. We use simulation studies to demonstrate that this approach, hOUwie, can accurately evaluate parameter values across a broad set of models. We then apply our model to test whether fleshy and dry fruits of Ericaceae lineages are correlated with their climatic niche evolution as represented by the aridity index. Consistent with expectations, we find that dry fruits have higher rates of climatic niche evolution, that the climatic niche of fleshy fruits is more conserved, and dry fruits have a more humid climatic optimum.