Phylogenetic comparative method for geographical radiation

Phylogeny can provide information about the processes that have shaped extant diversity. Here, we complement existing comparative phylogenetic methods by developing a model that couples diversity-dependent diversification rate and range dynamics. Unlike many models, we used Approximate Bayesian Computation to fit the model to the data. We validated the inference by estimating known parameter values from simulated data, and found that within-region speciation and extinction rates cannot be simultaneously estimated most likely due to correlations among parameter values. Since the model can estimate a diversification rate, we applied the model to a monophyletic lineage of 74 species of dung beetles (Canthonini: Nanos and Apotolamprus) endemic to Madagascar. The estimated diversification rate is clearly higher in northern than in eastern or western Madagascar. The current species richness is highest in North where complex topography and a mixture of biomes likely favour ecological diversification. The approach we have developed here is a step towards examining weaknesses and strengths of phylogenetic comparative methods in an explicit spatial context. Further development and testing of the model is needed before its routine application to empirical data. © Finnish Zoological and Botanical Publishing Board 2017.