3.2 Phylogenetic analysis of O.sinensis
A ML phylogenetic tree of 20 taxa was inferred using 14 conserved PCGs associated with the OXPHOSsystem.Ophiocordycepssinensis was most closely related to Hirsutella rhossiliensis，with a bootstrap value of 100%(Fig.2)，and these species then formed a sub-cluster with H.minnesotensis and Tolypocladium ophioglossoides.The cluster of these four fungi is consistent with the traditional classification that they are all in Ophiocordycipitaceae.As Lin et al.(2015)found，all entomopathogenic fungi formed a cluster in this ML phylogenetic tree，including the fungi in Clavicipitaceae(Metarhizium and Metacordyceps)，Cordycipitaceae(Cordyceps，Beauveria and Lecanicillium)，and Ophiocordycipitaceae(Hirsutella，Ophiocordyceps，and Tolypocladium)，while three Fusarium plant pathogens were clustered together.The topology of the ML tree agreed with that based on Bayesian inference，but differed slightly from the topology obtained using the NJ method.In the NJ tree，T.ophioglossoides was clustered with M.chlamydosporia and M.anisopliae，and the fungi in Cordycipitaceae branched earlier than in the ML tree.The ML phylogenetic relationship inferred from the mt genome is principally consistent with the current Pezizomycotina taxonomic system(Taxonomy Database in NCBI).
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Fig.2 ML phylogeny of O.sinensis based on 14 PCGs in mt genome
The phylogenetic tree was inferred from a concatenated alignment of 14 PCGs(atp6，atp8，atp9，nad1-nad 6，nad4L，cob，and cox1-cox3)using ML analysis.Numbers above branches specify bootstrap percentages(500 bootstrap replicates).MEGA 7.0 was used to determine the best evolutionary model(GTR+R)and RAx ML 8.0 was used to infer the phylogenetic tree.