An experimental test of colonization traits at a patch-scale in Andean Neotropical streams

Characterizing dispersal traits can further our ecological understanding of Neotropical stream macroinvertebrate communities, allowing us to test fundamental questions about disturbance and functional diversity responses in these systems. We combine observational and experimental approaches to measure short-term colonization of cobbles by stream invertebrates at five headwater streams arrayed along a habitat stability gradient in the Ecuadorian Andes, along with conducting drift and benthic surveys along the same gradient. Cobbles were sampled for benthic macroinvertebrate community composition and basal resource accrual at five time points over the 23-day experimental period. We found that taxonomic richness did not show clear trends across colonization time. Invertebrate community composition in the cobble colonization experiment did not approach the background benthic and drift composition over colonization time. Focal taxa showed variation in their drift and colonization propensities, with no clear relationship to habitat stability. We also found that benthic communities from less stable streams differed greatly between experimental years, highlighting the need to account for intra- and interannual differences in colonization experiments.