Colonization routes of benthic macroinvertebrates in a stream in

southeast Brazil

CARVALHO¹, E.M. & UIEDA¹, V.S.

¹ Departamento de Zoologia, CP 510, UNESP – Universidade Estadual Paulista, 18618-000 Botucatu, SP, Brasil.

Email: ecarvalho@ibb.unesp.br; vsuieda@ibb.unesp.br

 ABSTRACT: The colonization of the benthic substrate by macroinvertebrates of a tropical stream was investigated through four routes: downstream movement, upstream movement, movement from the subsurface and colonization by aerial source. Traps were built and installed to quantify separately each route. Samples were removed after 1, 3, 7, and 21 days of colonization. The community showed two main characteristics: the dominance of two groups (Chironomidae and Baetidae) and a progressive increase in richness and density in a temporal scale. Although this dominance occurred at all routes, they differed in relation to the total richness, total density, community composition, and over time. The density of the main groups sampled differed significantly among routes only at the 21st colonization day. When considered the percentage density by each route (only at 21 colonization day) for the ten most common taxonomic groups, three patterns can be pointed out. (1) Seven taxa used the four routes (Chironomidae, Trichoptera, Baetidae, Leptophlebiidae, Copepoda, Leptohyphidae and Elmidae), (2) one taxa used three routes (Annelida), and (3) two taxa used only two routes (Simuliidae and Glossosomatidae). In this study, the four colonization routes were important for replacement of denuded areas. Groups of benthic macroinvertebrates, which used preferential routes, determined the differences in community structure between different colonization routes.

Key-words: dispersal movements, colonization, invertebrates, artificial substratum, experimental manipulation, tropical stream.