Influence of leaf litter composition on ant assemblages in a lowland tropical rainforest in Thailand

In tropical rainforests, variability in the distribution of soil and litter arthropods is usually explained at regional scales by altitude, soil nutrients, and disturbance regimes. However, the influence of these factors on insect assemblages at the micro-habitat scale has rarely been studied. We investigated whether the species identity of decomposing leaves in tropical forest affected the composition of ant assemblages around them. Ants were extracted from litter below three common tree species, Parashorea stellata (Dipterocarpaceae), Intsia palembanica (Fabaceae) and Shorea gratissima (Dipterocarpaceae) in a 24 ha lowland rainforest plot in southern Thailand. A total of 2,257 individual ants, representing 71 species in 38 genera of 6 subfamilies were collected in the dry and wet seasons during 2010. Ant species richness was never significantly different among litter samples under the crown cover of three tree species. Ant species richness was higher in the wet season than the dry season. Our results demonstrate that ant assemblages are seasonally heterogeneous. Leaf mass and litter mass did not relate to the presence of ant diversity. Soil humidity was the only important factor influencing ant diversity in this study. Future studies should consider the importance of soil moisture related to litter ant diversity.