Phylogeny and sexual selection in the dance fly species group Enoplempis (Empis, Empidini)

Sexual selection is an evolutionary process that can result in the evolution of complex behavioural, morphological and physiological traits in many groups of organisms. It is thought to be a key driving force of the evolution and diversification of hyperdiverse groups. An example of a group where sexual selection may have a significant effect on phylogenetic diversity are Dipterans in the family Empididae. The evolution of mating behaviour in the Empis subgenus Enoplempis is one such interesting system of study. This group exhibits a variety of stages of nuptial feeding behaviours culminating in ballooning behaviour. Kessel (1955) hypothesized that this species group has evolved in stages from offering large prey items with much nutritional benefit to frothy balloons which contain crushed fragments of prey with little nutritional benfit. Members of this species group also exhibit morphological ornamentations whose evolution may also be driven by sexual selection. Enoplemis offer an ideal opportunity to study the possible effects of sexually selected traits on the evolution of diversity in the wider Empidini in a phylogenetic context. Here are presented the intial findings of the phylogeny of Enoplempis and their implications for the evolution of ballooning behaviour.