Padrões de riqueza, abundância e coocorrência de macroinvertebrados em riachos interceptados por cachoeiras no cerrado tocantinense

Abstract

Different factors are invoked to explain how species are distributed in the environmental gradient, especially with regard to structuring patterns of co-occurrence. The immature fauna of Ephemeroptera, Plecoptera and Trichoptera (EPT) are commonly found in streams intercepted by waterfalls and these can generate patterns of co-occurrence through disturbances. The objective here is to verify whether the distance from the waterfall influences the appearance of co-occurrence patterns of EPT immatures in streams of the Cerrado region of Tocantins. We believe that patterns of co-occurrence are more evident upstream of waterfalls with more abundant genera in drought. The work was carried out in four waterfalls in Taquaruçu, Palmas-TO. Five points above and below the waterfalls were sampled during the dry and rainy periods. We performed a co-occurrence analysis of the genera to demonstrate possible segregation patterns and GLM analyzes to verify if the waterfall influenced the richness and abundance of EPT. We collected 2,532 specimens from 33 genera, 12 families and five trophic guilds. Only a few negative associations were significant in the co occurrence (drought), where none occurred upstream of the waterfalls, nor with more abundant genera. GLM showed that EPT diversity can be influenced by the dry season, upstream position and distance from the waterfalls. Therefore, the waterfall is not a structuring factor that influences the emergence of patterns of co-occurrence. The EPT community appears to be randomly structured, due to patterns of richness and abundance as a function of the distance and position of the waterfall and the dispersal capacity of the group.