The Plecoptera – who are they? The problematic placement of stoneflies in the phylogenetic system of insects

Abstract

There is no consensus about the relations of Plecoptera with other insects. Very different sistergroup relationships have been proposed in the literature, several of which are discussed. The phylogenetic analysis is hampered by the diversity among Plecoptera. In the literature, traits of particular subgroups of Plecoptera have sometimes been mistaken as typical of the entire order. A plea for revived interest in plecopteran morphology is made in order to document the existing diversity and to establish the ground pattern of important structures for meaningful comparisons with other insects. A possible sistergroup relationship between Plecoptera and the remaining Neoptera, on the one hand, and a sistergroup relationship with the Polyneoptera on the other hand, seem most likely. Suggested close relationships of Plecoptera with Embioptera and Phasmatodea are refuted. Molecular data so far also failed to provide robust phylogenetic hypotheses for the placement of Plecoptera.