Colonization of leaf litter by aquatic macroinvertebrates: a study in a low order tropical stream (original) (raw)

Colonization of leaf litter by aquatic macroinvertebrates: a study in a low order tropical stream. The streambed of low order tropical streams is composed mainly by dead leaves and tree branches originated from riparian forest. This substratum is decomposed by physical, chemical and biological factors, and can be colonized by a characteristic fauna. The colonization dynamics of these substrates by macroinvertebrates can reflect how they use the multidimensional space of the environment. This work aimed to investigate if the colonization of leaf litter by macroinvertebrates depends of the composition of leaf litter. Three representative species of the riparian forest of the Fazzari stream, in São Carlos, SP, were chosen: Cecropia pachystachya, Calophyllum brasiliensis, and Talauma ovata. Four treatments were used, with leaf litter bags containing leaves of each isolated species and a fourth treatment with a mixture of the species. Replicated bags were placed into the stream, and recovered after 7, 21 and 35 days. The colonizing fauna was analyzed in relation to the taxonomic structure, relative taxon abundance, and functional structure (feeding guilds). Only C. brasiliensis presented differences of faunal colonization in relation to the other treatments, with fewer taxa (12) and functional feeding groups, and the lowest abundance of colonizing individuals (80). T. ovata and the mixed substratum were mainly colonized by macroinvertebrate shredders (e.g., Endotribelos spp. and Phylloicus sp.), presenting the greatest number of taxa (23 and 21), and abundances (357 and 271). These patterns suggest that leaf litter colonization was strongly influenced by the quality of the resources represented by leaves from different tree species.