Does fragmentation alter species composition in Ant communities (Hymenoptera: Formicidae)?

We tested if fragmentation alters ant species (Hymenoptera: Formicidae) composition, through the similarity of species composition within the remnants with matrix habitat. We sampled 17 tropical forest remnants and adjoined grassland matrix. Species composition was altered by fragmentation, because although total species richness increased with remnant area, the proportion of generalist ant species (occurring both in the matrix and in the forest) decreased. Four mechanisms may explain the above patterns : (i) fragmentation changed conditions inside the remnants, favoring species formerly only present in forest gaps; (ii) isolation effects changed the pool of species able to colonize different remnants; (iii) fragmentation increased invasion by generalist species, through the increase in perimeter/area ratio and conditions more similar to matrix habitats; and (iv) area reduction is higher than perimeter reduction. Smaller remnants lose more species than larger ones and receive less species from the matrix than large remnants, which explains the patterns found.