Figure 2.

A phylogeny of the Plecoptera, constructed by using a NJ analysis with sequence data from the 18S gene. Taxa below Ostrocerca are outgroups. Numbers on the left of nodes indicate bootstrap support (1,000 replicates; only values over 70% are shown). The asterisk marks the node separating the superfamily Nemouroidea from the more derived taxa; although not well resolved by the 18S sequence data alone, this node has a bootstrap support value of 89 in a MP analysis that combines 18S sequence data with morphological character data. Underlined taxa are those included in our phylogenetic analysis that are known to be surface skimmers or that initiate flight by jumping from the water (3–7); taxa not underlined have not been sampled (except Scopura, which is wingless and therefore incapable of any form of winged locomotion, and the Perlidae, which we have never observed to skim). Icons to the right of each underlined taxon show the type of behavior used by that species. A version of this figure containing links to video recordings of the behaviors is available at http://www.bio.psu.edu/People/Faculty/Marden/PNASFig2.html.