Phylogenomics, Classification, and Revisionary Studies of Meniscus Midges (Diptera: Dixidae)

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Aquatic insects are contributors to nutrient processing and water purification, serve as model organisms in ecological research and environmental monitoring and assessment, and are prey items for vertebrate predators. As a consequence of the latter, many are valued as bait or models for artificial lures (i.e., “flies”) in recreational fishing. Order Diptera, or “true flies”, comprises a substantial portion of aquatic insect diversity. Dixidae, one such family commonly known as “meniscus midges”, are the focus of this study. These mosquito-like flies are best known for their unique larvae, which are adapted to live at the air-water interface (hence the common name) surrounding emergent rocks or vegetation. They are often seen swimming laterally on the water’s surface or resting in a characteristic U-shaped posture. Dixidae, when compared to related groups, have received far less attention from scientists. This is due in part to the lack of medical importance and a paucity of taxonomic experts for the family. Furthermore, studies of Dixidae have historically focused on regional faunas, rather than global, more comprehensive treatments, leading to large gaps in our knowledge. As a result, the taxonomy of Dixidae is confusing and poorly resolved, and relatively little is known about the natural history of most species. If left uncorrected, this quagmire represents a serious impediment to future research on the family. The solution is a complete overhaul of the current classification of world Dixidae based upon results of an integrative morphological and molecular phylogenetic study. A greater understanding of dixid evolution is not only important in its own right, but also valuable because it lends insight into the evolution of their blood feeding, pestiferous relatives: mosquitoes, black flies, and biting midges. Extensive training of students and early career scientists in current and emerging technologies with relevance to general and molecular biology, bioinformatics, and phylogenetics will be incorporated throughout this study so they will be poised to meet rapidly developing challenges facing 21st century biologists. A robust phylogenetic hypothesis will significantly aid in stabilizing the classification of Dixidae and promulgating future research. Specimens needed for this study will be acquired through museum loans and necessary fieldwork. The current taxonomic quandary and the extremely limited public awareness of this family will be remedied by completing the following research and outreach objectives: (1) complete thorough systematic revisions of the entire family (Tier 1: supraspecific groups) and targeted subclades (Tier 2: Nearctic genera Dixa & Dixella, Gondwanan genus Nothodixa) using a combined morphological and phylogenomic approach, the former gleaned from all life stages after the egg and the latter DNA sequences representing hundreds of genes from the nuclear genome; these studies will yield morphology-based (dichotomous and multi-access keys, high-resolution photographic images, detailed illustrations, interactive 3-D models) and molecular-based (raw data, sequence alignments, phylogenetic inferences) outputs; (2) develop DNA-fingerprinting resources, both mitochondrial and nuclear, to allow for rapid, reliable identification of world species; (3) refinement and completion of a novel approach to mine phylogenetically informative markers from short-read genomic libraries using a reference mapping approach as well as accompanying pre- and post-mapping bioinformatics pipelines, all of which are intended to be carried out within a user-friendly graphical user interface (GUI) setting; and (4) through in-person and internet-based outreach programs, foster an appreciation for the scientific method, critical thinking, and natural sciences using aquatic insects as model organisms, engaging predominantly underserved youths who may otherwise receive little exposure to science.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.