Phenotypic Ecological Performance And Transcriptome Analyses Of The Two Geographic Populations Of Agasicles Hygrophila In Response To Heat Stresses

Agasicles hygrophila is an important biological agent to control alligatorweed,Alternanthera philoxeroides.In china,field surveys showed that the decline in the A.hygrophila population from early August to late September in summer resulted in difficulties in effectively controlling the population of A.philoxeroides in Changsha city,Hunan province,but this beetle can feed on A.philoxeroides at that period in Wanning city,Hainan province.In view of this phenomenon,the theories and techniques of population ecology and high-throughput sequencing technology used to reveal the countermeasure between defense and reproduction of the two A.hygrophila geographical populations under heat shock.In this study,how high temperature affect the fluctuation of A.hygrophila populations discussed.The differences of reproduction between the two populations under high temperature were tested,and molecular base of the regulation mechanism under high temperature investigated.Key finding are present as following:1.Under high temperature stress,fecundity of A.hygrophila female reduced and survival rates of female and male declined.Alternanthera hygrophila female and male undergone heat shock temperature(39°C(4h)+ 25°C(20h))and suitable temperature(30°C(4h)+ 25°C(20h)),respectively.We set up four treatments as following: 30°C♀×30°C♂(in control),30°C♀ × 39°C♂,39°C♀ × 30°C♂ and 39°C♀ × 39°C♂.The results showed that the fecundity and the hatchability of offspring eggs were significant differences among four treatments.At the same treatment,female fecundity,survival rate and egg hatching rate of A.hygrophila offspring significantly decreased with the heat shock time extending.Under heat shock condition,the fecundity of A.hygrophila female was more sensitively than that of male.2.High temperature over 36°C significantly affected the growth development and reproduction of A.hygrophila.High temperature stress was a hamful factor to A.hygrophila population grow.Under30°C(4h)+ 25°C(20h)and 33°C(4h)+ 25°C(20h)treatments,The fecundity,developmental period and survival rates were no significant difference between A.hygrophila Changsha geographical population and Hainan geographical population at successive three generations.Two A.hygrophila geographical populations well developed at 30°C(4h)+ 25°C(20h)and 33°C(4h)+25°C(20h)treatments.Under 36°C(4h)+ 25°C(20h)and 39°C(4h)+ 25°C(20h)treatments,the fecundity of A.hygrophila Changsha geographical population and Wanning geographical population significantly reduced,the developmental periods significantly prolonged and survival rates significantly declined.Under 39°C(4h)+ 25°C(20h)treatment,two A.hygrophila geographical populations failed to complete two generation.3.Under periodically repeated heat events,the reproductive capacity and survivability of A.hygrophila Wanning geographical population were better than those of Changsha geographical population.Under 30°C(4h)+ 25°C(20h)treatment,successive three generations of female fecundity and other life parameters between geographical Changsha population and Wanning geographical population were no significant difference.Under 33°C(4h)+ 25°C(20h)treatment,the female fecundity of A.hygrophila Wanning geographical population was significantly higherthan that of Changsha geographical population at the third generation.Under 36°C(4h)+ 25°C(20h)and 39°C(4h)+ 25°C(20h)treatments,the female fecundity,female longevity,egg hatching rate and larval survival of Wanning geographical population were significantly higher than that of Changsha population.Under 39°C(4h)treatments,the female fecundity of Wanning geographical population was 232.8 eggs per female,and 102.4 eggs per female of Changsha geographical population.4.Based on high-throughput sequencing technology,ovarian transcripts of two geographical populations of A.hygrophila at high temperature and suitable temperature detected.69328 unigenes were gained.The differentially expressed genes analyzed.It found that the ovary of the two geographical populations had different regulation methods in response to high temperature stress.Various metabolic systems used to respond to high temperature stress.More energy distributed to the resistance in the A.hygrophila Changsha geographical population.In our study,we found that the extreme high temperature disturbed the fluctuation and development of A.hygrophila population mainly by affecting the female reproduction and the survival of female and males.Between Wanning geographical population and Changsha geographical population have different regulation methods in response to high temperature stress.The Changsha geographical population would allocate more energy to the resistance.