Odonate assemblages of running waters in the Upper Guinean forest

Abstract

In order to describe the assemblages of adult Odonata of running waters in the Upper Guinean forest, 36 sites in Liberia and Ghana were analysed using Non-met- ric Multidimensional Scaling. Five groups were identified, which correspond with dif- ferent assemblages in the sequence of habitats from small streams to large rivers. Tax- onomically related species demonstrate distinct ecological segregation within this gra- dient, occupying different sections of running waters, or different microhabitats therein. The balance of sun and shade, resulting from a varying degree of habitat open- ness, is thought to be an important factor in habitat selection, but it is difficult to dis- tinguish from other factors associated with stream size. Anthropogenic opening of stream habitat (e.g. by deforestation or damming) can downscale the present fauna, i.e. result in the invasion of species of downstream habitats (more open) and the disap- pearance of upstream (dense forest) species.