02451nas a2200181   4500008004100000022001400041245011300055210006900168260000800237300001600245490000800261520179100269100001802060700002502078700002602103700003102129856010902160       2010                        eng d  a0025-316200a{The role of habitat heterogeneity in structuring the community of intertidal free-living marine nematodes.}0 arole of habitat heterogeneity in structuring the community of in  cjan  a1741–17530 v1573 aThe role of habitat complexity has been widely neglected in the study of meiofaunal community patterns. We studied the intertidal nematode community of a structurally complex macrotidal beach exhibiting contrasting microhabitats (sandbars and runnels) to understand the influence of environmental gradients and habitat heterogeneity in the community structure. We tested whether topographical complexity affected (1) the zonation pattern in terms of abundance and diversity, and (2) local diversity by promoting compartmentalization into distinct faunal groups. Our analyses revealed three major faunal assemblages along the exposure gradient associated to differences in mean grain size and chlorophyll a. Diversity patterns involved a mid-intertidal peak, consistent with the intermediate disturbance hypothesis, and another peak at the limit with the subtidal region, consistent with the transition zone. These results highlight the predominance of environmental gradients in establishing intertidal zonation. However, microhabitats differed in environmental conditions and possessed significantly distinct nematofaunal communities. Runnels featured higher levels of taxonomic and functional diversity, many unique genera, and the community differed from the assemblage at the limit to the subtidal, stressing their role as distinct microhabitats. The nematofauna of the structurally complex beach was more diverse than the one from a homogeneous beach nearby, supporting the hypothesis that structural heterogeneity promotes diversity by compartmentalization and highlighting the importance of microhabitats in the assessment of biodiversity. Contrary to previous predictions, our results indicate potentially high regional marine nematode diversity in the Upper Gulf of California.1 aGingold, Ruth1 aMundo-Ocampo, Manuel1 aHolovachov, Oleksandr1 aRocha-Olivares, Axayácatl  uhttp://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=3873037{&}tool=pmcentrez{&}rendertype=abstract