| Blaberidae,the third most speciose blattodean family,comprise model species for studies on endocrinology,biomimetics,sociality and reproductive behavior.Also,blaberid cockroaches' ancestry could track back to the Mesozoic,with the diversity and widespread distribution make them relevant models to investigate complex biogeographic scenarios.Thus,reconstructing the phylogeny of Blaberidae and formulating a phylogeny-derived robust classification will be benefit for these researches mentioned above.Phylogenetic studies of Blattodea based on multiple gene sequences,complete mitochondrial genomes and even transcriptomes have been a main developing trend,however,researches about the phylogeny and the divergence dating analyses of Blaberidae are still lacking,relationships among the twelve subfamilies remain controversial.Therefore,we acquired the mitochondrial genomes and two nuclear genes(18S rRNA and 28 S rRNA)of 29 Blaberids species,putting emphasis on subfamilies which were distributed in China(Epilamprinae,Panesthiinae and so forth).And then,we preformed the phylogenetic analyses and evolutionary study of Blaberidae based on those data,as well as data downloaded from NCBI.Meanwhile,we conducted the study on the comparative mitochondrial genomics of Blaberidae,including analyses of base composition,evolution rate and relative synonymous codon usage.The main results are listed as follows:The variation in the length of mitochondrial genomes among different subfamilies and genus is not obvious;the base composition is stable and exhibits positive AT-skew;the evolution rate of COI gene is slowest while ATP8 gene is the fastest;there is no gene rearrangements occurred in 29 species belonging to 6 subfamilies;anticodons of tRNA genes are common anticodons in invertebrates.We presented the phylogenetic estimate of Blaberoidea based on the complete mitochondrial genomes(excluding D-loop region)and from 3 different datasets.Both Maximum likelihood(ML)and Bayesian inference(BI)analyses were performed.The results show that Blaberoidea is monophyletic,being sister to Ectobiidae;Oxyhaloinae is found to be the sister group of Diplopterinae;the sister group of Panchlorinae is Gyninae;a sister relationship between Perisphaeriinae and Panesthiinae is also proposed.Meanwhile,Rhabdoblattellinae subfamily nov.is proposed to accommodate Rhabdoblattella;Phoetalia is transferred from Blaberinae to Zetoborinae;Geoscapheinae should sink to Panesthiinae with the included species;Perisphaerinae is founded to be paraphyletic,and then two genus,Laxta and Neolaxta are transferred to Epilamprinae according to the molecular studies.Thus,the phylogeny of the Blaberoidea is suggested as Rhabdoblattellinae+Epilamprinae+((Pycnoscelinae+((Oxyhaloinae+Diplopterinae)+((Blaberinae+Zetoborinae)+(Gyninae+Panchlorinae)))+(Paranauphoetinae+((Panesthiinae+Perisphaeriinae)+Epilamprinae))).We inferred the evolutionary timescale of Blaberoidea with BEAST,using 12 fossil calibrations.The late Jurassic period(about 162.17 Mya)was suggested the origin of the family(95% CI 138.33-189.61 Mya).Within the Blaberidea,the earliest division of these taxa was Rhabdoblattellinae,144.17 Mya(95% CI 120.72-169.87 Mya);two sister genera Epilampra maya+Galiblatta cribrosa subsequently diverged 134.91 Mya(95% CI112.74-158.86 Mya)from other taxa;the lineages leading to Pycnoscelinae+Oxyhaloinae+Diplopterinae+Blaberinae+Zetoborinae+Gyninae+Panchl--orinae and Paranauphoetinae+Panesthiinae+Perisphaeriinae+Epilamprinae diverged128.79 Mya(95% CI 105.91-151.25 Mya).We also found a number of divergences within and between some families suggest that their distributions should been shaped by transoceanic dispersal events.During examining the Blaberid species,we found two new species in the genus Rhabdoblatta: Rhabdoblatta terminata sp.nov.;Rhabdoblatta maculosa sp.nov.Besides,a method of species delineation,Automatic Barcode Gap Discovery(ABGD),is proved to be effective in discerning species,with 24 species identified by morphology are well supported by the result of ABGD. |
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