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.
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