Study On Differencial Biological Characteristics And Geographical Distribution Of The Sibling Pests,Ectropis Grisescens And Ectropis Obliqua

Ectropis grisescens Warren and Ectropis obliqua Prout are leaf-eating sibling species which seriously damaged the tea garden.It is difficult to distinguish between E.grisescens and E.obliqua because of the similar morphological characteristics and biological habits.They always have been regarded as one kind of tea geometrid,which cause the previous papers about biological characteristics,sex pheromone components and virus kinds of tea geometrid are different from the actual situation.In the current study,the potential differences of biological characteristics between E.grisescens and E.obliqua were characterized and compared based on laboratory observation to clear the difference between them.Besides,mitochondirial DNA cytochrome oxidase(mt DNA COI)gene was utilized as makers to identify species of collections in Zhejiang province and China to figure out their geographical distribution and distribution patern,providing reference for the filed control.The results are as follows:1.The potential differences between their biological characteristics especially the body-length,weight,developmental duration and population growth rates of each development stage were characterized and compared.First,the body-lengths and weights of the old larvae,pupae and moths were significantly different,with higher levels observed on E.grisescens in comparison to those of E.obliqua.Similarly,the periods of one generation between these two pest species were distinct.E.grisescens needed 36.6 days to complete one generation,whereas E.obliqua required at least 39.7 days.Finally,the generational survival rate and population growth rate in E.obliqua was 0.28 and 24.9,respectively,which was approximately two times lower than that of in E.grisescens,generational survival rate(0.6)and population growth rate(58.1).Hence,we proposed that E.grisescens had larger body size,faster developmental rate and stronger reproductive capacity than E.obliqua.2.COI gene was utilized as makers to identify species of collections from 17 counties in Zhejiang province,and the geographical distribution of the sibling pests were analyzed.The results showed that the species from 11 locations were completely E.grisescens and the species of other three locations(Anji,Yuhang,Longwu)were completely E.obliqua among 17 counties.There are three co-occurrence areas of the sibling pests.The results indicate that E.grisescens is widely distributed in cities and counties except Huzhou and Jiaxing,while the distribution of E.obliqua is narrow,only in Hangzhou and Huzhou.3.Nineteen populations collected from 11 provinces were determined based on the genetic divergence in the COI region of the mtDNA,and their geographical distribution was analyzed.The results showed that the 11 locations are only distributed with E.grisescens;3 locations(Huzhou,Yuhang,Wuxi)are distributed with E.obliqua only,and another 5 locations are potential mixed area with co-occurrence of two species.An overall pattern of the distribution of these two sibling species was concluded,i.e.,the single areas of E.grisescens are distributed in a wide range of tea areas in China,while the single areas of E.obliqua are limited to the borders of Zhejiang,Jiangsu and Anhui provinces;mixed areas geographically connect two single areas of E.grisescens and E.obliqua,respectively.