Evolutionary history of stomach bot flies in the light of mitogenomics

Abstract

AbstractStomach bot flies (Calyptratae: Oestridae, Gasterophilinae) are obligate endoparasitoids of Proboscidea (i.e. elephants), Rhinocerotidae (i.e. rhinos) and Equidae (i.e. horses and zebras, etc.), with their larvae developing in the digestive tract of hosts with very strong host specificity. They represent an extremely unusual diversity among dipteran, or even insect parasites in general, and therefore provide significant insights into the evolution of parasitism. The phylogeny of stomach bot flies was reconstructed based on extensive mitochondrial genomic data for Cobboldia, Gyrostigma and six of the eight known species of Gasterophilus. The phylogenetic tree, i.e. {Cobboldia, [Gyrostigma, (Gasterophilus pecorum, (Gasterophilus intestinalis, (Gasterophilus haemorrhoidalis, Gasterophilus inermis)), (Gasterophilus nasalis, Gasterophilus nigricornis))]}, provides a strong evolutionary reference to infer several biological patterns for the first time for this group: (i) host shifts of stomach bot flies from elephants to rhinoceroses and then from rhinoceroses to equids; (ii) dispersal with their hosts from the Afrotropical region into the Palaearctic and Oriental regions; (iii) oviposition site, originally on the host head, and egg production positively correlated with distance from the mouth; (iv) attachment of third‐instar larva originally in the stomach, with duodenal and large intestinal positions secondarily derived; and (v) guanine and cytosine enrichment of the mitogenome as an adaptation to larval life in the warm environment of the host digestive tract, combined with the need for a high evolutionary rate to cope with the fast evolution of their mammalian hosts.