Complex temporal dynamics of insect metacommunities along a tropical elevational gradient

Unraveling the spatiotemporal dynamics of communities is critical to understand how biodiversity responds to global changes. However, this task is not trivial, as these dynamics are quite complex, and most studies are limited to few taxa at small local and temporal scales. Tropical mountains are ideal indicators of biodiversity response since these endangered and complex ecosystems include many distinct habitats within small geographical areas, harboring a megadiverse fauna, especially insects. Indeed, while insects are particularly sensitive to environmental and climatic changes, the extent of the impact of climate variability on mountain tropical insect diversity remains poorly understood. Here we present time-series data from a decade of studying the spatiotemporal dynamics of ants, butterflies and dung beetles. We assessed patterns of species richness change along the elevational gradient for each taxonomic group per sampling year and cumulatively over years. We then quantified community changes over time by measuring the variation in species richness across sampling years (temporal trends in α-diversity), and the temporal variation in species composition (temporal β-diversity) evaluating species gains and losses over time. We also evaluated the variation of air temperature and humidity through meteorological stations within the sampling years. We detected a classical pattern of species richness decline with elevation, albeit with a noticeable increase in species richness variation with increasing elevation. The temporal β-diversity exhibited considerable variability across elevations, taxa, and time. Only dung beetles presented a positive relationship with humidity variation over the years. Critically, both rare and common species drove extirpations and colonizations, and we found no trend of temporal decline of insect species at local and regional scales. Our study shows that insect metacommunity responses to elevation and global changes are rather complex, and stresses the importance of long-term studies that incorporate multiple sampling periods and different groups of organisms in tropical mountains.