The dance flies (Diptera: Empididae: Empidinae), a lineage of over 2,000 species, exhibit a suite of specialized mating behaviors and morphology that place them among the most commonly cited examples of sexual selection in insects. They are the subject of many detailed behavioral studies and textbook examples. This collaborative study integrates molecular, behavioral and morphological data collection to develop a comprehensive evolutionary classification for the Empidinae. Evolution of behavior and sexual morphology is studied within specific focal clades to identify key traits involved in swarming, sex-role reversal, presentation of nuptial gifts ("ballooning"), and intersexual conflict. Genetic data are used to frame and inform tests of evolutionary hypotheses concerning generation of diversity in dance flies and examine the implication of these findings other organisms. Project results will test long-standing hypotheses on mating system evolution and provide key empirical evidence in support of the hypothesized link between sexual selection and diversification rate dynamics in a diverse lineage of insects.
The project involves academic training and a program of outreach, including educational material that will be presented via the project website, and online resources for undergraduate and K-12 levels.
The dance flies (empidines) include over 2,000 species and are well known in the insect world for their mating swarms and specialized behaviors. The males of some species provide the female with a prey item or silken balloon as a nuptial gift during copulation. Others form large swarms of males or females from which the opposite sex chooses mates by evaluating unique features of their anatomy such as expanded flag-like hairs on the legs or expanded wings or abdomens. These mating strategies make these flies the subject of many detailed behavioral studies and textbook examples of the process of sexual selection in evolution. The high species diversity of dance flies however makes them a difficult group to identify, study, and classify. Intensive study of the genetics, behavior, and morphology of dances flies can provide new estimates of genetic relationships of dance flies to test hypotheses about the history of mating system changes and the effects these changes have on the origin of new species. These studies place the discovery and description of dance fly species, along with their behavior and anatomy into an organized, evolutionary, and predictive classification for further research. This project involved a team of researchers assembled to investigate the relationships of these organisms with molecular and anatomical data to improve their classification and to investigate the history of their speciation and behavioral change. This was accomplished in a series of studies that were conducted and are published. Project-based field work led to discovery of new species of Empis (Enoplempis) that construct silk balloons as nuptial gifts, and a species that exhibits a unique asymmetry in a mate-attracting leg feature of the males. Analysis based on anatomical features has brought many new species previously unknown to science, to light. Analysis of genetic data from a broad sample of empidine species reveals a new pattern of relationships among the major lineages and reveals that mate swarming behaviors are an ancestral feature for the group and that nuptial gift giving, ballooning, and many elaborate anatomical features evolved multiple times independently throughout the 95 million year history of this fly group. This project involved a postdoctoral researcher, graduate, and undergraduate students, as well as collaborators from Canada, France, and Brazil. The results improve understanding of these insects that were otherwise poorly known, and the revised classifications are being used to understand evolutionary processes associated with mating systems, geographic distributions, and habitat change. Examples of dance fly evolution are now available for use by educators and other researchers. In addition to disseminating the results of this project to other researchers through traditional publications and conference proceedings, members of the project team delivered numerous presentations in the United States and abroad to local people, teachers, and students.
