Ant Species Distribution Models Reveal Mixed Elevational Diversity Patterns in Complete Elevation Gradients: Past and Present Climatic Effects?

Abstract

The juxtaposition of climatic zones in tropical mountains is considered one of the leading causes of the high diversity of tropical mountains; high peaks block oceanic winds, causing mid-elevation peaks of precipitation and diversity. Also, historically wind-protected valleys may harbor high species richness because of climate stability. Despite this knowledge, the elevational patterns of many taxa and their drivers remain unsolved. We aimed to describe the spatial patterns of ants’ diversity in the Jamapa River watershed in Mexico based on species distribution models of 253 ant species. Moreover, we intend to understand the relationship between ant diversity with the current climatic conditions and historical climatic stability. The watershed includes maximum elevations of 5636, 4282, and 2500 m from south to north and is exposed to the oceanic northeastern winds. Elevational patterns of species richness were consistent with theoretical predictions but changed south (mid-elevation peaks) to north (monotonic decrease) in the watershed. Species richness was positively associated with mean annual temperature and precipitation seasonality. Climatically stable sites harbored high species richness below 2100 m of elevation but low species richness above 2400 m, while the beta diversity showed the opposite pattern. We observed that present climatic conditions and historical climatic stability were essential drivers of ant diversity in the Jamapa River watershed. Elevational patterns of species richness were concordant with theoretical expectations. They changed from a monotonic decrease of diversity to marked mid-elevation peaks of species richness, presumably associated with the maximum height of the mountains.