Systematics And Taxonomy Of Platypodinae In Jiangxi Province Inferred By Morphological And Molecular Characteristics

The Platypodinae(Coleoptera: Curculionidae)are commonly referred to as pin-hole borers or ambrosia beetles.They are economically and ecologically important wood-boring beetles and important quarantine insects.There were 21 species of ambrosia beetles reported in mainland China,and only one species was reported in Jiangxi province.This study was focused on the systematics and taxonomy of the subfamily Platypodinae of Jiangxi Province.Platypodinae specimens were collected in Jiangxi province between 2016-2018.They were examined morphologically using existing lituerature.Among them,16 species were identified.A key to the genera present in Jiangxi was provided.I also explored the feasibility of using DNA barcoding to identify Platypodinae species based on mitochondrial cytochrome c coxidase subunit ?(CO?).The phylogenetic relationship of Platypodinae species based upon five molecular markers was constructed.The detailed results are shown as the following:1.Based on morphological characteristics,16 Platypodinae species were collected in Jiangxi,including 3 new species(Crossotarsus beaveri sp.n.,Platypus cavatus sp.n.,Platypus jiulianensis sp.n.),2 new Chinese records(Platypus vethi,Diapus minutissimus),3 new Chinese mainland records(Crossotarsus sauteri,Platypus levannongi,Diapus truncatus)and 6 new Jiangxi records(Crossotarsus terminatus,Dinoplatypus calamus,Dinoplatypus flectus,Platypus contaminatus,Platypus sinensis,Treptoplatypus solidus).All species were described in detail and their hosts,distribution information and figures of males and females were provided.2.Based on the 658 bp sequence of mitochondrial CO? gene in this group,the genetic distance among different species varied from 0.154 to 0.319 with the average value of 0.214,while that among the same species ranged from 0 to 0.021 with the average value of 0.006,and there was no significant distinction from different geographical populations,confirming that the genetic distance can be used to distinguish different species.Neighbor-joining and maximum likelihood phylogenetic trees were built based on this specific gene sequences,and the results revealed that the same species was grouped in the same branch,with the bootstrap value of 100%.The consequence suggests that DNA barcoding of CO? specific fragment is feasible for Platypodinae species identification.3.The phylogeny 16 Platypodinae species from Jiangxi province was reconstructed based on the combined sequences of five markers and each marker by maximum likehood(ML)and Bayesian inference(BI)methods.The results show that the phylogenetic tree topology and clade node support based on single markers were slightly different in the ML and BI trees.But the Bayesian and maximum parsimony analyses of the combined nucleotide data produced very similar tree topologies and higher support.All phylogenetic trees were consistent with that based on morphology at the tribe level,but inconsistent at the genus level.Individuals with the same species were grouped together in the same branch.Because of the in consistencies in the phylogenetic relationships at the genus level,more samples and genetic markers need to be tested in future studies.