Spatial scale influences diversity patterns of free-living nematode assemblages in coral degradation zones from the Caribbean Sea

Diversity of marine nematodes in coral degradation zones (CDZs) has been poorly studied despite of its contribution to global coral reef diversity; additionally, effects of spatial scales on nematode assemblages are also largely unknown. To fill this gap, we studied the marine nematode assemblages in CDZs from two coral reefs in the Caribbean Sea to describe the diversity, test the effects of spatial scales, and explore if there were adaptive biological trait combinations. We sampled 2 reefs (Ballenatos and Punta Frances), 6 sites, and 20 dead coral piles in a fully nested design identifying the nematodes to species level. CDZs harbored a diverse nematode assemblage of 112 species with large spatial turnover. Differences between reefs in abundance and species density were probably related to differential energy availability, with Punta Frances receiving larger input of material and energy from land. The spatial scale had a significant effect on the species richness, whereas differences in species composition were mainly driven by the scale at which ecological drivers operated (10(-1) m for interstitial heterogeneity vs. 10(5) m for dispersal). Geographical distances in the order of 180 km likely constituted barriers to nematode dispersal and as such promoted assemblage dissimilarity. Our evidence indicated that a particular set of biological traits favored the adaptation of nematodes to CDZs, namely a distinctive combination of armed stoma, ornamented cuticle, and conical tail.