Fine-scale climatic variation drives altitudinal niche partitioning of tabanid flies in a tropical montane cloud forest, Ecuadorian Chocó

In montane systems, global warming may lead communities to disassemble by forcing organisms to shift their distributions to higher elevations or by causing the extinction of those that are unable to adapt. To predict which species are most at risk from environmental change, physiological responses to multiple factors must be measured in natural conditions at fine spatial and temporal scales. To examine the potential drivers of elevational distributions in tabanid flies, specimens were exhaustively sampled at three altitudes within a tropical montane cloud forest in Western Ecuador. Observed abundances were then correlated with seven environmental variables measured in situ. It was hypothesised that (1) tabanid distributions were significantly associated with particular environmental conditions measured in each altitudinal habitat, and (2) a greater proportion of lowland species were limited to a specific elevation than highland species. Most species occupied well-defined altitudinal niches corresponding to optimal climatic conditions. Colder weather, higher daily temperature variability, and higher levels of moisture seemed to limit most species from establishing in high elevation sites of this mountainous ecosystem. Despite the high dispersal potential of tabanids within the study area, results suggest that most tabanid flies are limited to the subset of altitudes where their climatic requirements are satisfied.