Molecular Phylogeny Of Gryllidae Inferred From Cyt B Gene (Orthoptera: Grylloidea)

Gryllidae is a large family in Grylloidea (Insecta: Orthoptera: Endifera). Most species of the family are agricultural pests and some can be used for entertainment or medical and edible resource. In the past years, its morphology, stridulation and cytology had been studied. Only a few molecular taxonomic work had been done. Based on mtDNA Cyt b gene, this study reconstructed its phylogeny and offered some evidences to the classfication of Gryllidae.With universal primers, partial sequences (579bp) of 35 individuals in Gryllidae, including 7 genus 18 species, had been sequenced. By analysing the components,the saturation of substitution,the bias of basepairs and phylogenetic signal of these sequences, we reconstructed its phylogenetic relationship of Gryllidae. The conclusions are as follows:1) The 35 sequences of Gryllidae presents a high A/T bias: among these sequences, the average percentage of A+T is 69% (A=32.6%, T=36.4%, C=20.8%, G=10.1%), while C+G is 30.9%. The average percentage of A+T in the 3rd position of the codon is the highest. Transitions are slightly higher than transversions (R=1.1) which depend on the velocity of evolution, especialy in the 3rd position obviously. Transitions mostly occur between T and A, and not deals with between C and G;transversions mostly occur between T and C. The use of codon and ammonia acids present a distinct bias.2) Molecular phylogenetic trees of Gryllidae had been reconstructed by several methods. The results conformed with the taxonomic views. The relationship of these genera is ((Goniogryllus, Qingryllus) (Loxoblemmus ((Teleogryllus, Gryllus) (Velarifictorus, Gryllodes )))). Goniogryllus and Qingryllus are original clades.The cladistic analysis shows Teleogryllus is closer to Velarifictorus which presents a more distant relationship to Loxoblemmus.3) Different methods were used to reconstruct the phylogenetic trees of Loxoblemmus. The results will be showed as follows: the relationship of these species is (L. angulatus ((L. taicoun, L. equestris) (((L. doenitzi, L. detectus) L. aomoriensis) L.haani )));L. taicoun and L. equestris are original clades;support the view of considering L haani and L. detectus as two different species, respectively. The status of L. angulatus and L. aomoriensis needs extensive study.4) The sequences of Cyt b gene to 10 individuals of L. doenitzi collected from 5 regions shows that these sequences are exactly the similar with each other. Which proved Cyt b gene is very stable among different individuals of the same species. Maybe the range of region and gene chosen is appropriate.5) Compared with the complete Cyt b gene sequence of Gryllus {Gryllus bimaculatus) from GenBank, we found that these 35 sequences locate the latter part and include many signal sites. The results show that different methods could reconstructed the same trees, and every branch present a high supported values, which proves that the relationships between genera and between species are very distinct. So we conclude that the Cyt b gene is suitable to solve the phylogenetic relationships at the lever of family or genus.