Species and functional group composition of ant communities across an elevational gradient in the Eastern Himalaya

Abstract

• First results on ant species composition change from Eastern Himalaya. • Species loss, not turnover, forms major part of total composition change. • Species diversity within each functional group decreased towards high elevation. • Functional group composition showed greater diversity and eveness at low elevation than at high elevations Elevational gradients in mountains show rapid changes in environmental conditions across a small geographic extent. This results in habitat specialization in animal communities which results in changes in species composition across space. We explore changes in species and functional group composition of ants using the first ever data on the distribution of ants across an elevational gradient in the Eastern Himalaya. Ants were sampled from 600 to 2400 m elevations at 200 m intervals using Winklers and pitfall traps. The sampling yielded 166 species of ants from 10,560 individuals, which were then classified into functional groups. We used redundancy analysis to test the effects of environmental factors (temperature, leaflitter volume, understory vegetation) and spatial predictors on species as well as functional group composition of communities at different elevations. Our results show that species diversity within all functional groups decreases towards higher elevations. The functional group composition of ant communities shows a gradient from high evenness at low elevations to being dominated by opportunist species at higher elevations. Redundancy analyses shows that most of the variation in species as well as functional group composition is driven by spatially structured environmental variation. This is most likely due to the high correlation between temperature and elevation. In summary, the changes in species as well as functional group composition are likely driven by a gradient in climate across the elevation gradient.