Eating down the food chain: generalism is not an evolutionary dead end for herbivores

The role of trophic specialisation in taxonomic diversification remains unclear. Plant specialists diversify faster than omnivores and animalivores, but at shorter macroevolutionary scales this pattern sometimes reverses. Here, we estimate the effect of diet diversification on speciation rates in noctilionoid bats, controlling for tree shape, rate heterogeneity and macroevolutionary regimes. We hypothesise that niche subdivision among herbivores positively relates to speciation rates, differing between macroevolutionary regimes. We found the rate at which new herbivorous lineages originate decreases as rates of diet evolution increase. Herbivores experience higher speciation rates, but generalist herbivores and predominantly herbivorous omnivores speciate faster than specialised herbivores, omnivores and animalivores. Generalised herbivory is not a dead end. We show that analysing ecological traits and diversification requires accounting for macroevolutionary regimes and within‐ and between‐clade variation in evolutionary rates. Our approach overcomes the high false‐positive rates of other methods and illuminates the roles of herbivory and specialisation in speciation.     

The role of frugivory in the diversification of bats in the Neotropics

Aim Ecological interactions are among the most important biotic factors influencing the processes of speciation and extinction. Our aim was to test whether diversification rates of New World Noctilionoidea bats are associated with specialization for frugivory, and how this pattern differs between the mainland and the West Indies. Location The New World. Methods We reconstructed a time‐calibrated molecular phylogenetic hypothesis for the New World genera of the superfamily Noctilionoidea. We compiled data on diet, morphology, geographical distribution and number of ecoregions in which each genus occurs. Then, using the phylogenetic tree constructed, we tested whether diversification was driven by diet (animalivorous and sanguinivorous versus nectarivorous and frugivorous) and specialization for frugivory. Afterwards, we conducted phylogenetic comparative analyses to identify correlates of species richness and net diversification rates. Results The diversification rate was higher in mutualistic than in antagonistic clades in mainland and Antillean biogeographical scenarios, but only strictly frugivorous clades showed a markedly higher diversification rate than the rest of the genera. Geographical range and number of ecoregions were positively associated with species richness and diversification rate in continental and insular lineages. Lower body mass, lower forearm length and specialization for frugivory were significantly positively correlated with higher diversification rates in continental lineages, whereas these parameters were negatively correlated in Antillean lineages. Main conclusions The direction of the relationship of intrinsic factors (specialization for frugivory and body size) with diversification of noctilionoid bats depends on the biogeographical context, whereas the direction of the relationship of extrinsic factors (geographical range and number of ecoregions) with diversification is consistent in both mainland and the West Indian lineages.