Molecular Phytogeny And Evolution In Calyptratae Flies With An Emphasis On Evolution Of The Oestroidea

With nearly 23,000 described species,calyptrate flies(Diptera:Calyptratae),consisting of Hippoboscoidea,Oestroidea and muscoid grade,representing 20%of dipteran diversity,make up the largest and most ecologically diverse clade within the schizophoran super-radiation,and is the key to investigate history of evolution and radiation of Diptera.The Calyptratae are distributed world-widely,and exhibit enormously diverse living habit,especially for the larvae.Larval calyptrates are herbivorous,predatory,sarcosaprophagy,coprophagy,and kleptoparasitism or obligate parasitism,indicating they are one of the most adaptive dipteran groups.The phylogeny and evolutionary history of calyptrates are well resolved except for the Oestroidea,with the family-level relationships within the Oestroidea almost entirely open,and biology of many groups still missing.With newly sequenced transcriptomic data of 38 calyptrate species[including seven oestrid species from three subfamilies which are parasites of mammals,one hippoboscid species and one Protocalliphora sp.(Calliphoridae)which are parasites of birds],this study aimes to construct calyptrate phylogeny using transcriptomic/mitogenomic data,determine classification of key groups(i.e.,Calliphoridae and Oestridae)and trace the evolutionary history of divers living habits of calyptrates.The major findings are described as following.1)By constructing transcriptomic phylogeny of the Calyptratae following dense taxon sampling and using specific Dipteran orthologous reference,we obtained monophyletic blow flies(Calyptratae:Calliphoridae),with traditional blow flies,Calliphorinae,Lucillinae and Chrysomyiinae paraphyletic.We hereby suggest to split the former calliphorid into Ameniidae,Bengaliidae,Calliphoridae,Chrysomyidae,Helicoboscidae and Polleniidae.The oestrid flies being paraphyletic,which is great conflict with morphology-based hypothesis,and the morphological similarities might be the result of bot flies having experienced convergence evolution.2)The subfamily-level phylogeny of Sarcophagidae(Diptera:Calyptratae)is inferred as(Sarcophaginae,(Miltogramminae,Paramacronychiinae))based on transcriptomic data for the first time.A sarcophagid phylogeny with the broadest coverage of genera to date was constructed with a supertree approach,which enabled us to trace the evolutionary history of the Sarcophagidae,showing(a)a Neotropical origin of the Sarcophaginae,and north Hemisphere origin of the Miltogramminae;(b)sarcosaprophagy as the ancestral larval feeding habit of the Sarcophagidae and all three subfamilies;(c)miltogrammine kleptoparasitism as the response to cold and adrid arid environment during evolution and derived from sarcosaprophagy in buried vertebrate carrion;(d)being kleptoparasites of predatory wasps shifting selection stress from males into females,resulting the male Terminalia simplified.3)The phylogeny of stomach bot flies(Calyptratae:Oestridae,Gasterophilinae)was reconstructed based on extensive mitochondrial molecular data for Cobboldia,Gyrostigma and six of the currently known eight species of Gasterophilus species.The phylogenetic tree,i.e.(Cobboldia,(Gyrostigma,(Gasterophilus pecorum,(Ga.intestinalis,(Ga.haemorrhoidalis,Ga.intermisinermis)),(Ga.nasalis,Ga.nigricornis)))),provides a strong evolutionary reference to infer several biological patterns for the first time for this group:(a)host shifts of stomach bot flies from elephants to rhinoceroses and then from rhinoceroses to equids;(b)dispersal with their hosts from the Afrotropical region into the Palearctic and Oriental regions;(c)oviposition site,originally on the host head,and egg production positively correlated with distance from mouth;(d)attachment of 3rd-instar larva originally in the stomach,with duodenal and large intestinal positions secondarily derived;and(e)guanine and cytosine(GC)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.