Non-flying and flying macroinvertebrates show similar beta diversity patterns caused by different factors at two spatial scales in Amazon streams

Abstract

We evaluated the beta diversity patterns of aquatic macroinvertebrate assemblages at two spatial scales in streams in the Eastern Amazon, as well as tested whether environmental and spatial factors affected these assemblage patterns differently for non-flying (i.e., shrimps) and flying (i.e., insects) macroinvertebrate groups. Fifteen streams were sampled, focusing on two hierarchical spatial levels: sampling units (length: five meters) and stream sites (length: 150\xa0m). We additively partitioned gamma diversity to test the relative importance of each spatial level to regional diversity. The total beta diversity at each spatial level was decomposed into the components of replacement and abundance difference. To test whether there was an effect of spatial distances and environmental variables on the dissimilarity matrices, we used multiple regression on distance matrices (MRM). Our results showed that: (1) In both macroinvertebrate groups, alpha diversity contributed less than beta diversity, and dissimilarity between stream sites presented a greater contribution to gamma diversity; (2) the decomposition of beta diversity showed similar patterns in both groups and between the two spatial levels, with a greater contribution of abundance difference than replacement; and (3) the MRM models showed that only environmental distance was important to explain beta diversity of insects, while for shrimps both environmental and spatial distances were significant. We conclude that different ecological processes and environmental variables were important to explain the distributions of insects and shrimps, which is probably related to the different dispersal modes and environmental niche requirements.