Are tropical ant and termite assemblages along a forest recovery gradient habitat or dispersal limited?

Nina Grella, David A. Donoso, Jörg Müller, Ana Falconí-López, Annika Busse, Marcel Püls, Dominik Rabl, Heike Feldhaar

Regenerating forests comprise a significant proportion of forest ecosystems in the tropics. While we are beginning to understand assembly mechanisms of tree communities after anthropogenic disturbances, those of animal communities are still poorly understood. It has been shown that locally established ant communities clearly assemble along gradients of forest recovery from active agriculture over the time of succession to old growth forests. However, if this is determined by dispersal limitation or habitat filtering is unclear. To disentangle the two processes for ant and termite communities we compared community composition of dispersing and sessile life stages for both based on OTUs, in a forest landscape of about 200 km2 extend in the Chocó lowland tropical forest in Ecuador. Our chronosequence comprises a recovery gradient ranging from agricultural land to regenerating forests to old-growth forests. Our results show that winged reproductives (alates) of both taxa disperse into all regeneration stages along the gradient, but communities were more similar in spatially closer plots suggesting that alates of both taxa have the potential to reach and colonize forests of all regeneration ages, but dispersal distances are smaller than the spatial extent of our study area. Worker ant communities originating from sessile nests were driven by forest regeneration age and elevation, suggesting that ants can disperse into different regeneration stages, but not all species establish colonies in all regeneration stages and elevation. Termite worker communities were likewise more similar at similar elevation and less similar in spatially closer plots, which might be explained by species specific habitat preferences for certain elevations and by biotic interactions such as local competition for resources. These results suggest, that both taxa are only dispersal limited on the larger landscape scale, and while ant communities are more affected by the habitat filtering (abiotic and biotic conditions) of the forest structure along the chronosequence, termite communities seem to be more affected by intraspecific competition.