Temperature and productivity distinctly affect the species richness of ectothermic and endothermic multitrophic guilds along a tropical elevational gradient

ABSTRACT

The diversity of endotherms and ectotherms may be differently affected by ambient temperature and net primary productivity (NPP). Additionally, little is known about how these drivers affect the diversity of guilds of different trophic levels. We assessed the relative role of temperature and NPP in multitrophic guilds of ectothermic (arthropods ants, ground beetles, spiders, and harvestmen) and endothermic (large mammals) animals along a tropical elevational gradient. We sampled arthropods at eight elevation belts and large mammals at 14 elevation belts in Atlantic rainforest (ranging from 600 to 2450 m.a.s.l.) of Itatiaia National Park, Southeast Brazil. Overall arthropod species richness was more associated with temperature than overall large-mammal species richness, while the latter was more associated with NPP. When separated into trophic guilds, we found that the species richness associated with NPP increased across arthropod trophic levels from herbivores to predators. Conversely, although NPP influenced large-mammal herbivore species richness, its effects did not seem to accumulate across large-mammal trophic levels since the species richness of large-mammal omnivores was more associated with temperature and none of the variables we studied influenced large-mammal predators. We suggest that thermal physiological differences between ectotherms and endotherms are responsible for the way in which arthropods and large mammals interact with or are constrained by the environment. Furthermore, the inconsistency regarding the role of temperature and NPP on species richness across multitrophic guilds of ectotherms and endotherms could indicate that thermal physiological differences might also interfere with energy use and flux in the food web.