Macroinvertebrate colonization of two different tree species leaf packs (native vs. introduced) in a Mediterranean stream

Allochthonous leaf litter from riparian vegetation represents the main energy source in small lotic systems, where canopy limits autochthonous primary production. In this study, leaf packs of two tree species (the native Salix neotrichia and the introduced Populus x canadensis) were positioned in the Fardes Stream (southern Spain) to analyze the macroinvertebrate colonization. On two dates, leaf packs were removed, and colonizing macroinvertebrates were collected and identified; at the same time, Surber samples were collected to characterize the riverbed macroinvertebrate coenosis. Leaf packs attracted rich and varied communities of benthic macroinvertebrates, with an increase of the abundance of most taxa over time. No significant differences were found between the colonizing communities of the two leaf types. Some macroinvertebrate species showed a preference for leaf packs, probably due to trophic or hydrologic factors. Considering functional feeding groups, increases in shredders and scrapers and decreases in predators and filterers were detected over time, while collector-gatherers almost did not change in abundance.