Temperature boosts and constrains dung beetle diversity along an Andean-Amazonian elevation gradient

In the light of a warming climate, understanding factors shaping tropical biodiversity becomes increasingly urgent. Temperature can enhance diversity by increasing diversification and ecological rates but may also restrict diversity when exceeding organisms' thermal limits. Changes in diversity can subsequently influence community specialization patterns. We tested the influence of temperature, moisture and food availability on the diversity of dung beetles (Scarabaeinae), food specialization and the mechanism of thermal limits along an Andean-Amazonian gradient from 250 to 3500 metres above sea level (m.a.s.l.). Beetles were sampled with dung, carrion and fruit-baited pitfall traps to test specialization; mammal activity was recorded as a proxy for food availability. Diversity showed no significant relationship with mammal biomass but increased with higher temperatures to 500 m.a.s.l., with a sharp drop at lower elevations. Lowland diversity was restricted by upper thermal limits, with small or negative thermal safety margins. Resource specialization increased towards the lowlands, potentially a product of greater diversity. Our findings highlight temperature as a primary driver of diversity, with upper thermal limits acting as a key constraint in lowland areas. Our data suggest that additional warming of the Amazonian lowlands may have detrimental consequences for dung beetles and their ecosystem functions, even in intact rainforests.