Frontiers of Biogeography

Arthropods are a major component of ecosystems, in terms of both their biomass and the variety of functional roles they play. Yet we lack a clear understanding of how arthropod abundance changes along environmental gradients. We compiled published literature on overall arthropod abundances (number of individuals) along elevational gradients and performed a formal meta-analysis on the role of latitude, climatic variables, and interactions with ants in shaping the pattern. Specifically, we asked if patterns of arthropod abundance along different elevational gradients are associated with gradients of seasonality and precipitation and whether ant abundance affects other arthropods. Arthropod abundance peaks at higher elevations at mid-latitudes than low latitudes; hence, the correlation between arthropod abundance and elevation shifts from negative to positive with an increase in latitude. We suggest these patterns reflect a steep elevational gradient in the length of growing season at mid-latitudes, with the short growing season at high elevations in mid-latitudes leading to synchronous emergence and reproduction of arthropods generating a sharp increase in abundance. Precipitation and ant abundance do not have a consistent effect on arthropod abundance along most elevational gradients. However, on gradients with a very dry base and sharp increase in precipitation with elevation, arthropod abundance peaks at higher elevations. Overall, our results suggest that future changes in the length of growing season will impact the elevation at which summer arthropod abundance peaks and the sharpness of the peak, likely affecting diversity and distribution of other taxa that interact with arthropods.