Evolution, multiple acquisition, and localization of endosymbionts in bat flies (Diptera: Hippoboscoidea: Streblidae and Nycteribiidae).

Bat flies are a diverse clade of obligate ectoparasites on bats. Like most blood-feeding insects, they harbor endosymbiotic prokaryotes, but the origins and nature of these symbioses are still poorly understood. To expand the knowledge of bacterial associates in bat flies, the diversity and evolution of the dominant endosymbionts in six of eight nominal subfamilies of bat flies (Streblidae and Nycteribiidae) were studied. Furthermore, the localization of endosymbionts and their transmission across developmental stages within the family Streblidae were explored. The results show diverse microbial associates in bat flies, with at least four ancestral invasions of distantly related microbial lineages throughout bat fly evolution. Phylogenetic relationships support the presence of at least two novel symbiont lineages (here clades B and D), and extend the geographic and taxonomic range of a previously documented lineage ("Candidatus Aschnera chinzeii"; here clade A). Although these lineages show reciprocally monophyletic clusters with several bat fly host clades, their phylogenetic relationships generally do not reflect current bat fly taxonomy or phylogeny. However, within some endosymbiont clades, congruent patterns of symbiont-host divergence are apparent. Other sequences identified in this study fall into the widely distributed, highly invasive, insect-associated Arsenophonus lineage and may be the result of symbiont replacements and/or transient infections (here clade C). Vertical transmission of endosymbionts of clades B and D is supported by fluorescent signal (fluorescent in situ hybridization [FISH]) and microbial DNA detection across developmental stages. The fluorescent bacterial signal is consistently localized within structures resembling bacteriomes, although their anatomical position differs by host fly clade. In summary, the results suggest an obligate host-endosymbiont relationship for three of the four known symbiont clades associated with bat flies (clades A, B, and D).

Some like it hot: evolution and ecology of novel endosymbionts in bat flies of cave-roosting bats (hippoboscoidea, nycterophiliinae).

We investigated previously unknown associations between bacterial endosymbionts and bat flies of the subfamily Nycterophiliinae (Diptera, Streblidae). Molecular analyses revealed a novel clade of Gammaproteobacteria in Nycterophilia bat flies. This clade was not closely related to Arsenophonus-like microbes found in its sister genus Phalconomus and other bat flies. High population infection rates in Nycterophilia across a wide geographic area, the presence of the symbionts in pupae, the general codivergence between hosts and symbionts, and high AT composition bias in symbiont genes together suggest that this host-symbiont association is obligate in nature and ancient in origin. Some Nycterophilia samples (14.8%) also contained Wolbachia supergroup F (Alphaproteobacteria), suggesting a facultative symbiosis. Likelihood-based ancestral character mapping revealed that, initially, obligate symbionts exhibited association with host-specific Nycterophilia bat flies that use a broad temperature range of cave environments for pupal development. As this mutualism evolved, the temperature range of bat flies narrowed to an exclusive use of hot caves, which was followed by a secondary broadening of the bat flies' host associations. These results suggest that the symbiosis has influenced the environmental tolerance of parasite life history stages. Furthermore, the contingent change to an expanded host range of Nycterophilia bat flies upon narrowing the ecological niche of their developmental stages suggests that altered environmental tolerance across life history stages may be a crucial factor in shaping parasite-host relationships.

Global distribution and genetic diversity of Bartonella in bat flies (Hippoboscoidea, Streblidae, Nycteribiidae).

Recently, a growing number Bartonella spp. have been identified as causative agents for a broadening spectrum of zoonotic diseases, emphasizing their medical importance. Many mammalian reservoirs and vectors however are still unknown, hindering our understanding of pathogen ecology and obscuring epidemiological connections. New Bartonella genotypes were detected in a global sampling of 19 species of blood-feeding bat flies (Diptera, Hippoboscoidea, Nycteribiidae, Streblidae) from 20 host bat species, suggesting an important role of bat flies in harboring bartonellae. Evolutionary relationships were explored in the context of currently known Bartonella species and genotypes. Phylogenetic and gene network analyses point to an early evolutionary association and subsequent radiation of bartonellae with bat flies and their hosts. The recovery of unique clades, uniting Bartonella genotypes from bat flies and bats, supports previous ideas of these flies potentially being vectors for Bartonella. Presence of bartonellae in some female bat flies and their pupae suggests vertical transmission across developmental stages. The specific function of bartonellae in bats and bat flies remains a subject of debate, but in addition to pathogenic interactions, parasitic, mutualistic, or reservoir functions need to be considered.