Turnover‐Dominated β‐Diversity and Its Temperature and Trophic Drivers of Scarabaeoidea Assemblages Along an Elevational Gradient in a Tropical Island Rainforest in China

ABSTRACT

Mountains serve as ideal natural laboratories for investigating biodiversity patterns along elevational gradients. This study examined α‐diversity (species richness and abundance) and β‐diversity (overall compositional dissimilarity and its turnover and nestedness) of Scarabaeoidea along an elevational gradient in a tropical rainforest, China. Scarabaeoidea assemblages were sampled continuously from early March to late November 2024 across 32 plots along an elevational gradient (371–1472 m a.s.l.) using ground and canopy traps. The aims were to evaluate the effects of potential drivers (temperature, humidity, litter biomass) and predator community (diversity and composition) on α‐ and β‐diversity. Scarabaeoidea species richness showed no significant relationship with elevation but increased with litter biomass. Scarabaeoidea abundance exhibited a pronounced mid‐elevational peak primarily driven by temperature, reflecting the strong thermal sensitivity of these ectotherms. Multisite β‐diversity was high ( β _SOR  = 0.893) and dominated by species turnover ( β _SIM  = 0.846). Pairwise β‐diversity ( β _sor ) of predator assemblages was positively correlated with that of Scarabaeoidea assemblages, suggesting the potential trophic effects on community structure. Elevational distance was positively associated with species turnover ( β _sim ) and β _sor , but negatively associated with nestedness ( β _sne ). Temperature distance remained a significant positive driver of turnover and β‐diversity and a negative driver of nestedness even after accounting for elevational distance. This study reveals that environmental filtering and trophic interactions jointly shape the assembly of Scarabaeoidea community in the Bawangling mountain. Our findings emphasize the importance of incorporating abundance and top‐down effects‐which may covary with environmental gradients‐when inferring the mechanisms structuring insect communities along elevational gradients.