Molecular phylogenetic analysis of evolutionary trends in stonefly wing structure and locomotor behavior. Journal   Proceedings of the National Academy of Sciences of the United States of America. Citation   Proc Natl Acad Sci U S A. 97(24):13178-83 Publication date   2000 Nov 21 Authors   Thomas MA Walsh KA Wolf MR McPheron BA Marden JH Investigators   James Marden Bruce McPheron MeSH headings   Evolution Insects Motor Activity Phylogeny Wing MeSH qualifiers   classification genetics physiology anatomy & histology Abstract   Insects in the order Plecoptera (stoneflies) use a form of two-dimensional aerodynamic locomotion called surface skimming to move across water surfaces. Because their weight is supported by water, skimmers can achieve effective aerodynamic locomotion even with small wings and weak flight muscles. These mechanical features stimulated the hypothesis that surface skimming may have been an intermediate stage in the evolution of insect flight, which has perhaps been retained in certain modern stoneflies. Here we present a phylogeny of Plecoptera based on nucleotide sequence data from the small subunit rRNA (18S) gene. By mapping locomotor behavior and wing structural data onto the phylogeny, we distinguish between the competing hypotheses that skimming is a retained ancestral trait or, alternatively, a relatively recent loss of flight. Our results show that basal stoneflies are surface skimmers, and that various forms of surface skimming are distributed widely across the plecopteran phylogeny. Stonefly wings show evolutionary trends in the number of cross veins and the thickness of the cuticle of the longitudinal veins that are consistent with elaboration and diversification of flight-related traits. These data support the hypothesis that the first stoneflies were surface skimmers, and that wing structures important for aerial flight have become elaborated and more diverse during the radiation of modern stoneflies. Medline ID   20542099