Habitat filtering, not dispersal limitation, drives ant and termite community assembly along a tropical forest...

Regenerating forests comprise a significant proportion of tropical forest ecosystems, yet species assembly mechanisms after anthropogenic disturbances remain poorly understood. Locally established ant communities follow predictable paths along forest regeneration gradients, but whether this results from dispersal limitation or habitat filtering is unclear. Social insects, with highly mobile dispersing reproductives (alates) but sessile colony stages, provide a window to disentangle these mechanisms. We compared assemblages of dispersing alates to workers from established colonies of ants and termites along a chronosequence in the Chocó lowland tropical forest, Ecuador. Our study area comprises a regeneration gradient where agricultural land, regenerating forests (1-37 years old), and old-growth forests are interspersed across a 200-km² landscape mosaic with short distances among land-use types. Alate assemblages of both taxa were independent of forest age but more similar in spatially closer plots. Worker ant assemblages were more similar at similar succession stages and elevations. Termite worker assemblages were more similar at similar elevations but more dissimilar in spatially closer plots. These results indicate that alates can disperse across all succession stages and elevations within our study area, but not all species successfully establish or persist everywhere. For ants, colony distribution is determined by habitat filters associated with forest age and elevation. For termites, colony distribution is influenced by elevation-related habitat filtering. Importantly, we found increasing species diversity with forest age for both taxa, underscoring the importance of advanced natural forest regeneration and old-growth forest conservation for maintaining diverse social insect communities.