Geographical Variation Of Acantholyda Posticalis Matsumura And Its Response Mechanism To Host Volatiles

Acantholyda posticalis（Hymenoptera: Pamohiliidae） is an important pine pest andwidely distributed throughout the Europe and Asia. It had caused serious damage to largeexpanses of forests worldwide. Understanding geographical variation of insect in themorphology, biology and other aspects, to adapt to different environmental conditions, is veryimportant for further study and management of pest populations. In this paper, we studied themorphologiacl difference of A. posticalis from different populations. At the same time thegenetic variation between different geographical populations of A. posticalis was analized bymolecular marker technology. The genetic relationships were revealed between Chinapopulations and Europen population by combining the genetic sequence information of A.posticalis from Europen population. Meanwhile, ultrastructure of the antennal sensilla and themain components of host volatiles were investigated for two populations with farthest geneticdistance. Finally, respones of the two sawfly population to the volatiles of their host pines weretested. The main results are as follows:(1) Morphology study shows there were signification difference in the body size, hadpatch, antenna pedicel patch, scute patch and the size of the male genitalia. The largst body sizeoccured in the central population and the smallest body size in the southwest population. Bodylenth of both male and female incresed with the increse of latitude which follow theBengermann’s rule. The body lenth of female incresed with the increse of longgtitude as well.Body lenth, wing expanse of both male and female had no significant correlation with altitude.The wing expanses of both male and female had no significant correlation with longtitude.Sexual size dimorphism index (SSDI) of central popilation is the largest and which ofsouthwest population is smallest. There was significant correlation between SSDI and latitude.(2) There were56mitochondrial DNA haplotypes in138samples from8populations.There were4haplotypes shared by multi-populations and52haplotypes belongs a single population. The HT12and HT43were main haplotypes and occurred in3populations and2populations respectively. The haplotype and nucleotide diversity of the eight geographicpopulations were0.962±0.006and0.04365±0.00224respectively. Analyses of molecularvariance (AMOVA) revealed that eight populations exhibited significant genetic differentiationwithin population (FST=0.26826， p<0.001) and among populations from single region(FSC=0.21046，p<0.001). The variability within population was73.17%. The genetic distancebetween southwest region and the middle region was the farthest (0.079-0.107) while thegenetic distance betwenn European population and population in northern region was closest(0.016-0.021). In haplotype networks, all haplotyes divided into three groups obviously. GroupA was consisted of haplotyes from southwest region and with the haploty HT12as its centre.Group B was consisted of north and eastern region. Group C was consisted of middle region.All of other haploty were evolved from HT12.(3) The antennae of A. posticalis are filiform, comprised32–35flagellomeres, and consistof scape, pedicel and a distal multi-segmented flagellum. Six sensillum types were found.Sensilla chaetica were straight setae with sharply-pointed tips and without dendrite in thelumen. Sensilla trichodea were characterized by a parallel-grooved wall and one terminal pore,innerved by4dendrites at the base. Sensilla basiconica I possessed longitudinally-groovedsurfaces and multiple terminal pores,5dendrites in the lumen. Sensilla basiconica II not onlyhad a distinct terminal pore but also had numerous tiny wall pores, numerous dendriticbranches within the sensillum lymph. Sensilla coeloconica had deep longitudinal grooves andone terminal pore, innerved by6dendrites, while s. campaniformia were thick-walled with aterminal opening and sensory nerve bundles in the lumen. Sensilla chaetica and s. trichodeawere most abundant and distributed over the entire antennae, while s. basiconica I and II, s.coeloconica, and s. campaniformia were restricted to the ventral flagellar surfaces. Althoughthe shape and structure of antennae were similar in males and females, females hadsignificantly longer antennae than males, and males had significantly more s. basiconica I thanfemales. The Yangquan population had more s. chaetica and s. basiconica II than the Wanrong population but substantially fewer s. basiconica I. In the Wanrong population, the s.coeloconica of males were longer and those of females shorter than in the Yangquan population.We compared the morphology and structure of these sensilla to other Hymenoptera anddiscussed their possible functions.(4) There were11main monoterpenes in host from two areas of two populations. Theywere R-(+)-α-pinene, S-(-)-α-pinene, S-(-)-β-pinene,(+)-3-carene, myrcene,(+)-limonene,(-)-limonene, γ-terpinene, α-terpinene, camphene, terpinolene. R-(+)-α-pinene, S-(-)-α-pinene,myrcene,(-)-limonene were main components. There were relative less amount ofS-(-)-β-pinene,(+)-3-carene,(+)-limonene and the γ-terpinene, α-terpinene, camphene,terpinolene were trace components. There was no significant difference between the twopopulations in term of monoterpene components and their contents. A. posticalis showedintensive response to (+)-3-carene, myrcene, γ-terpinene,(+)-limonene,(-)-limonene,α-terpinene and terpinolene, with the most significant response to (+)-limonene. There were nosignificant difference in response of two sawfly populations to11monoterpenes. There werepositive correlation between the response intensity of A. posticalis and the dose of (+)-3-carene,(-)-limonene and myrcene. When the dose of (+)-limonene, γ-terpinene and terpinolene was625ug, the response of A. posticalis reached saturation point and soon descend when the dosefurther increased. The response of A. posticalis from Wanrong population reach saturationpoint when the dose of α-terpinene was625ug while there was positive correlation between theresponse intensity of A. posticalis to the dose of α-terpinene from Yangquan population.