Thermal Adaptation Of Agasicles Hygrophila (Coleoptera: Chrysomelidae) In Responses To Temperature Stress

A host specific flea beetle,Agasicles hygrophila Selman & Vogt(Chrysomelidae) is an important natural enemy to control the alligator weed.There are different control effects on controlling alligator weed in different environment.In natural condition, population of A.hygrophila was decreased rapidly in hot summer,and was increased when the temperature was decline in autumn.Combinating the characteristics and seasonal changes in population trends of A.hygrophila in our country,we hypothesize the adaptability of tolerance of A.hygrophila to thermal stress may be one of the important factors,which may lead to seasonal population occurrence.In this paper,the experimental biology and ecology field research methods were used to study the adaptation of heat stress of flea beetle.The effect of heat stress on the reproductive capacity,survival of future generations and thermal adaptability of A.hygrophila were also measured in this study.The purpose of this paper will be revealed the reason of seasonal population changes of A.hygrophila.The main results of this study are as follows.1.Occurrence characteristic and population dynamics of A.hygrophila were studied.The results were showed that there were two fastigiums among the pond,marsh and garden,they were in June to July and October to November.In the same original number and density condition,the most population of A.hygrophila was occurred in the largest number in pond compared with marsh and garden.The occurrence population was the same in garden and marsh.2.The survivals of eggs,pupae and adult of A.hygrophila were decreased along with the increase of temperature and the delay of exposure time.The heat capacity of A. hygrophila eggs was worst in these three development stages.The A.hygrophila eggs were not hatched under 41℃for lh.While the survivals of pupae and adult of A.hygrophila had a high survival rate,they were 75%and 100%.The temperature,exposure time and their interaction were played the significant effect on the survivals of eggs,pupae and adult of A. hygrophila.3.The adult lifespan and fecundity were occurred to decrease along with the increase of temperature after the A,hygrophila adult was exposured to short-time and high-temperature.The adult lifespan was 37.4 days in 25℃,but only 20 days under 45℃for 1 h.The offspring survival was also decreased along with the increase of temperature, which directly affected the quantity and quality of offspring population.This study was defined the A.hygrophila population relationship between different habitats, and revealed that the low tolerance of thermal stress of A.hygrophila was one of the main reasons that lead to the population variation in seasonal dynamics.The results from our research can provide the practical evidence to protect and use of A.hygrophila.