Biogeographical history constrains climatic niche diversification without adaptive forces driving evolution

Aim: To evaluate the effect of biogeographical history on climatic niche diversification. Location: Simulated clades evolving in South America. Methods: We modelled species evolution under neutral community dynamics and purposely assumed that climatic niche is an emergent property of species. This assumption allows us to better understand whether phylogenetic niche conservatism could be observed when climatic niche is only constrained by biogeographical processes of dispersal and speciation. We varied speciation and dispersal probability, calculating phylogenetic signal of niche overlap and distance between niche centroids for each emergent artificial biota. We then compared the phylogenetic signal of our model with the expectation of climatic niche evolution under Brownian motion (BM). Results: We found that phylogenetic signal of climatic niche in the spatially explicit neutral model is usually higher than expected by chance, but lower than expected by BM evolution. Because simulated climatic niches have lower phylogenetic signal than expected by BM evolution, standard ecological and evolutionary interpretation would suggest that climatic niche evolved with little variation over time caused by strong evolutionary constraints. However, our model assumes that climatic niche does not evolve by adaptive forces and is only a consequence of stochastic dispersal and speciation over space and time. Main conclusions: Our study reinforces the strong imprints of biogeographical processes on climatic niche evolution, even when no adaptive forces are driving niche diversification. Therefore, although testing phylogenetic signal is the most common approach in studies evaluating phylogenetic patterns in climatic niche conservatism, our results reinforce previous claims that these patterns alone are not capable of distinguishing the possible effect of space in the retention of climatic niche. Biogeographical processes alone can leave imprints in patterns of climatic niche overlap between related species. A careful evaluation of macroevolutionary models underlying phylogenetic patterns of niche variation among species is important to avoid pitfalls related to interpretation of mechanisms of niche diversification.