Study On The Phylogeny And Classification Of Cephidae(Hymenoptera)

Cephidae is a peculiar small basal family of Hymenoptera.The larvae feed on the stalks of grass,the terminal shoots of the first and second years of woody plants.The niche is distinct from all other Hymenoptera.Including all the new genera and species described in this paper there are 37 genera and 229 species of world.Among them 24 genera and 110 species are found from China.The phylogeny of Cephidae was reconstructed based on the morphological and biological characters.The molecular phylogeny was reconstructed based on the mitochondrial genomes.Based on the morphological phylogeny and molecular phylogeny,a new classification system for Cephidae was proposed.Keys to subfamily,genera and species of the family are provided,as well as a complete list of genera and species,and their distribution data.The study chose 35 genera and 126 species as the inner group composed of representatives of the present genera,including all the type species of the present genera and the type species of those ever being proposed genera in Cephidae.Megaxyela fulvago,Pamphilius palliceps,Euxiphydria potanini,Sirex noctilio,Syntexis libocedrii of 5 Symphyta families were selected as the outgroup.Totally 126 morphological and biological characters were selected and determined.Using outgroup comparison method and referring to the general evolution trend of morphological characters within Cephidae,the characters are polarized and coded.TNT program(Tree Analysis Using New Technology)was used to reconstruct the phylogeny of Cephidae.Four final trees and 1 multiple consensus tree were constructed.The result shows:the monophyly of Cephidae were supported by many synapomorphic characters;the monophyly of the subfamilies Athetocephinae,Sulawesiinae,Australcephinae and Cephinae were strongly supported by a lot of synapomorphic characters;the monophyly of Athetocephinae including Sulawesiinae as an ingroup and Hartigiinae were not supported;Athetocephinae is the first basal lineage of Cephidae;Sulawesiinae and Australcephinae are the second and the third basal lineages;Within Cephinae four monophyletic lineages(in different color within the brackets)and nine monophyletic tribes are revealed.The sister groups of the ingroups of Cephinae are as Caenocephini +(Urosyristini+(((Jungicephini+Tibetajanini)+Janini)+(Syristini+(Hartigiini+(Pachycephini+Cephini)))));the monophyly of the complicated genus Cephus was denied and the monophyly of Janus was also problematic;the monophyly of Stigmatijanus,Magnitarsijanus,Calameuta and Trachelus was weakly supported.Based on mitochondrial genomes of 13 genera and 36 species of Cephidae(no representatives of Jungicephini,Tibetajanini and Caenocephini),using Web-version IQ-TREE and MrBayes programs,the molecular phylogeny of Cephidae was analyzed.The result shows:the sister groups within Cephidae are Urosyristini+(Janini+((Hartigiini+Pachycephini)+(Syristini+Cephini)));among them,Janini,Hartigiini,Cephini including Characopygus,Syristini including Meganijanus are monophyletic tribes;Characopygus is a member of Cephini and is the sister group of Calameuta;Magnijanus is not a member of Janus but a sister group of Neosyrista,and so the Syrista including Asian species is not a monophyletic genus;Sinicephus is possibly related to Pachycephini but this result is conflict with the morphological phylogeny;the general frame of the molecular phylogeny of Cephidae is similar to the morphological phylogeny except for the monophyly of Cephini and Pachycephini.Based on the morphological and molecular phylogenies,a new classification system of Cephidae was proposed according to the monophyly classification rule:Cephidae was classified into four subfamilies including Athetocephinae,Sulawesiinae,Australcephinae and Cephinae;Cephinae was divided into Caenocephini,Urosyristini trib.nov.,Jungicephini trib.nov.,Tibetaj anini trib.nov.,Janini trib.nov.,Syristini trib.nov.,Hartigiini,Pachycephini and Cephini.The following new taxa were described:Magnijanus Wei&Liu,gen.nov.,Xizia Wei&Liu,gen.nov.,Lineojanus Wei&Liu,gen.nov.from China;Genghiscephus Wei&Liu,gen.nov.from Central Asia;Xizia nigrostigma Liu&Wei,sp.nov.,Cephalocephus tianmunicus Liu&Wei,sp.nov.,Lineojanus elegans Liu&Wei,sp.nov.and Lineojanus formosus Liu&Wei,sp.nov.from China.Following genera were reestablished:Eversmannella Jakowlew,1891(move out from synonym of Pachycephus Stein,1876),Cephalocephus Benson,1946(move out from synonym of Urosyrista Maa,1994).Following new combinations were proposed:Eversmannella cruentatus cruentatus(Eversmann,1847)comb.nov.,Eversmannella cruentatus konowi(Kohl,1905)comb.nov.;Cephalocephus montanus(Maa,1944)comb.nov.;Magnijanus megamaculatus(Liu&Wei,2017)comb.nov..Morphological descriptions,variations,nomenclatures,specimens recorded,distribution data,identification and host information are provided.At the end of dissertation,the morphological features of the new taxa are provided.The type specimens of the new species are deposited in the Asian Sawfly Museum,Nanchang,China.