Convergent evolution in lemur environmental niches

Aim: To test the hypothesis that adaptive convergent evolution of climate niches occurred in multiple independent lemur lineages. 

Location: Madagascar

Taxon: Lemurs

Methods: I collected climate and altitude data from WorldClim and summarized the niches of almost all living lemurs (83 species) into phylogenetically-controlled principal components. To test for convergent evolution, I searched for multiple, similar climate optima using multi-peak Ornstein-Uhlenbeck models (surface, l1-ou, bayou). I compared the observed level of climate convergence to that simulated under neutral and single-optimum models. To test if behavioral or morphological traits were related to climate niches, I used phylogenetic regressions with activity pattern, diet, and body size.

Results: From an ancestral niche with high rainfall and low seasonality, four lemur lineages independently converged on climate niche optima characterized by high temperatures and low rainfall, supporting adaptive evolution in southwest deciduous and arid habitats. The observed level of convergence was more frequent than expected under Brownian motion and single-optimum simulations, which illustrates that the results are likely not a result of stochastic evolution over long time periods. Nocturnal and cathemeral activity patterns were common among lineages in the arid climate niche. 

Conclusion: Lemur climate niche evolution demonstrated that convergence explains the distribution of four independent clades in hot, arid environments of southwest Madagascar. The timing of these convergent shifts coincided with the origination of modern arid-adapted plant genera, some of which are important lemur food sources. These communities have high endemicity and are especially threatened by habitat loss. Arid environments are arenas in which convergent evolution is predicted to occur frequently.