UC Berkeley

Diptera has more species with an aquatic stage than any other insect group, yet their evolutionary history and its association with other traits, like blood feeding and marine dwelling, remain unknown. A comprehensive phylogeny of Diptera (flies) has recently been proposed, allowing for studies of adaptations across this diverse group. Ancestral state reconstruction analyses suggest marine dwelling is not an ancestral trait in the most recent common ancestor to Diptera. In addition, several families (e.g. Culicidae and Canacidae) of flies have independently adapted to saltwater found in the marine environment. For example, Canacidae (beach flies) is a cosmopolitan family that includes species that are found in intertidal ecosystems where their larvae feed on algae. The genus Procanace, in particular, offers the opportunity to study biogeography and the adaptation to novel freshwater environments. In this dissertation, a phylogeny of Procanace and relatives is reconstructed, based on multiple mitochondrial and nuclear DNA sequences from 15 species representing 5 genera. The reconstructed phylogeny supports the monophyly of the Procanace genus, which confirms previous taxonomic studies. In addition, the reconstructed phylogeny suggests that canacids colonized Hawai’i twice, once by an ancestor of Procanace and again by an ancestor of Canaceoides. Speciation patterns within the genus Procanace follow the progression rule and demonstrate a single switch from saltwater to freshwater habitats in the Hawaiian Islands. Although understudied, these flies may yield insights into freshwater invasions and pathways behind osmoregulatory systems. This dissertation also examines the evolution of aquatic life histories and their associations with blood-feeding across Diptera. The most recent common ancestor of Diptera is likely to have had an aquatic (but not marine) life history. When examing aquatic life history in relation to blood-feeding, we found that blood-feeding behaviors often occur in fly lineages that also have aquatic life histories, but not significantly more often. This pattern suggests that, in some cases, adaptations to larval aquatic life history were a precursor for flies expanding their diets to take blood meals. This work builds on our understanding of the ecological and evolutionary history of aquatic Diptera and its associations with blood-feeding.