Diversity of Anisoptera (Odonata): infering speciation processes from patterns of morphological diversity

With roughly 2500 described species Anisoptera are among the species-poor suborders within insects. However, morphological and ecological variability are truly impressive. Anisoptera are classified into about 15 families of variable species richness. In this analysis phylogenetic research is integrated with comparative approaches to investigate possible explanations of differential speciation rates within this suborder. A short review of phylogenetic work based on morphological characters is compared to published molecular phylogenies. Sistergroup comparisons are used to elucidate whether a) sexual selection, b) duration of life cycles, or c) differentiation in body size, have had a detectable effect on speciation rate. In all three analyses effects of distributional range and latitudinal distribution were controlled. These analyses suggest sexual selection promotes speciation and an increase in body size is positively correlated with speciation rate. The evolutionary significance of these results is discussed and experimental approaches that should advance our understanding of anisopteran diversity are suggested.