Species distribution modelling reveals the influence of climatic and geographic factors on scarab beetle beta diversity along altitudinal gradients

Abstract Beta diversity patterns result from the assembly of communities shaped by local and regional filters. However, understanding these patterns is limited by gaps in species distribution knowledge, especially for hyperdiverse groups. In this context, ecological niche modelling represents an effective approach to overcoming such limitations by providing robust species distribution predictions. In this study, we used the distribution models of 67 scarab beetle species to assess patterns of beta diversity and its components (species turnover and nestedness) across 14 elevational gradients on the coastal and inland montane slopes of El Salvador. We also analysed the effects of climatic (environmental filter) and geographic (dispersal filter) factors on beta diversity. Our results show that beta diversity decreased with increasing elevation, independently of geographic region, and that there were no significant differences in the relative contributions of turnover and nestedness between coastal and inland gradients. Environmental filtering (differences in temperature and precipitation) and dispersal filtering (spatial distance) were determinants in shaping the beta diversity patterns. These results indicate that the beta diversity of scarab beetles is determined by climatic and geographic factors. This integrative approach based on species distribution modelling underscores the importance of montane habitats for maintaining beta diversity and endemic species, highlighting the role of environmental heterogeneity and geographic location in shaping ecological assemblages. These findings emphasize the broader need for conservation strategies that preserve ecological diversity in complex landscapes, particularly under threats of habitat loss and climate change.