Mayfly distribution along a longitudinal gradient in Serra do Cipó, southeastern Brazil

GOULART¹, M. & CALLISTO¹, M.

¹ Universidade Federal de Minas Gerais, Instituto de Ciências Biológicas, Departamento de Biologia Geral, Laboratório de Ecologia de Bentos, CP. 486, Belo Horizonte, MG, Brasil, CEP. 30.161-970. callisto@icb.ufmg.br

ABSTRACT: The main goals of this study were to evaluate the spatial distribution of mayfly nymphs and substrate associations along a longitudinal gradient in two lotic ecosystems of the same watershed at Serra do Cipó, southeastern Brazil. The main questions addressed here were: 1) Do mayfly nymphs present longitudinal zonation? 2) Do mayfly nymphs present specific associations with the type of substrate? 3) Which are the main consequences of mayfly distribution for the conservation strategies of headwaters in the Serra do Cipó? Samplings were realized in 1st up to 6th order reaches of the Indaiá stream and Peixe River, during the rainy and dry periods of 2000 and 2001, totaling 234 samples. Regarding the longitudinal distribution, most of the taxa showed a gradient (clinal), or zone patterns, being restricted (or presenting higher densities) to a specific river reach or river section. The highest densities of Baetidae nymphs were found in 4th up to 6th order reaches while the Leptophlebiidae and Euthyplociidae were found in higher densities in the upstream reaches. The Baetidae taxa were found associated preferentially with aquatic macrophytes, while the Leptophlebiidae and Euthyplociidae with pebbles, gravel and sand deposits. The results evidenced differences in the taxonomic composition and abundance of the mayfly fauna along the longitudinal gradient. The distribution patterns and substrate associations call attention to the importance of the preservation of the natural characteristics of the altitudinal headwaters in Brazilian watersheds.

Key-words: Ephemeroptera, habitat diversity, substrate association, conservation, river ecology.