| The ragweed(Ambrosia artemisiifolia), Compositae, which originated in Sonoran area of North America, is a widely spread and worldwide weeds, mainly by seed reproduction. The ragweed is annual weed, which has a strong ecological plasticity, suitable for growth in a variety of different habitats, particularly in the area by human disturbance, easy to form a single advantage community. The ragweed is a serious threat to the invasion of biodiversity, farming, animal husbandry production as well as human health.Ophraella communa Lesage (Coleoptera:Chrysomelidae), native to North America, is a kind of insects suitable for the subtropical climate. In our country, the earliest recorded in May,2001, in Nanjing and the surrounding counties and cities were found to report, alien insects is newly introduced into China mainland. O.communa like to have ragweed, and the larvae often clustered, which appetite is big, host specificity is strong, the ragweed control effect is obvious. Now the O. communa is widely distributed in south China area of ragweed.As a kind of important specificity predators of malignant invasion weeds ragweed, O. communa Lesage whether can further to migrate to the north and over winter, as the key to control ragweed in northern area. This paper studies the different geographic population carries out developmental and reproductive characteristics and differences in the cold hardiness indexes of O.communa, aims to make clear O. communa adapt to adversity physiological mechanism in low temperature and predict the possibility of its gradually move north and establish population. The main results were as follows:1. The developmental and reproductive characteristics of O. communa in different geographic populationBy comparing Fogang in Guangdong, Lai bin in Guangxi, Nanchang in Jiangxi, Miluo in Hunan, Yangzhou in Jiangsu, Langfang in Hebei, the adult sex ratio in the six geographic populations overwintering generation, shows that as the latitude increases gradually, female sex ratio of the overwintering generation O. communa also gradually increased.Through hatchability of eggs, larva pupation rate and pupa eclosion rate of the six geographical population wintering F1generation comparison, the results show that three were not significant difference. The egg stage, larval stage and pupal stage of six geographical population wintering F1generation all have significant difference. With latitude increased gradually, the egg stage of the six geographical population wintering F1generation gradually shortened, and the pupal stage presents a gradually increasing trend, larval stage with latitude variation trend is not obvious.The female sex ratio, oviposition period, preoviposition, single female spawning, the longevity of male and female adult of six geographical population overwintering Fi generation, the results show there is no significant difference. By comparing the male and female adult life of the same geographic populations wintering F1generation, the male adult life is significantly longer than the female adult in Nanchang population, but for the other five geographic populations,there was no significant difference between male and female adult life.2. Cold hardiness of adult O. communa from different geographical populationsBy comparing the supercooling point, freezing point, water content of overwintering F1generation among the six geographical population, as the latitude increases gradually, the supercooling point of female O. communa in overwintering F1generation gradually reduce, but there is no significant difference among the male adults. As far as the male and female in overwintering F1generation of the same geographic populations, for the population of Fogang and Laibin, the cooling point of the male was significantly lower than the female, but there is no significant difference in the other four geographic populations. There is no significant difference about the freezing point in overwintering F1generation adults of the six geographical population, but the freezing point of male adult was significantly lower than the female adult of Fogang, there is no significant difference between the female and male among the other five geographic populations. With latitude increased gradually, the water content of the male and female adult in overwintering F1generation are gradually reduced, for male and female adult in overwintering F1generation of the same geographic population, there is no significant difference among the six geographic populations.The glycerin, lipid, total sugar content determination in overwintering F1generation of the six geographical population results showed that glycerin content differences of male and female adult were not significant in overwintering F1generation of the six geographical population. With latitude increased gradually, the lipid content of the female adult increases gradually, but there is no significant difference among the male adult. As far as the male and female adult in overwintering F1generation of the same geographic populations, the lipid content of Miluo population is significantly higher than the female adult, but there is no significant difference among the other five geographic populations. With latitude increased gradually, the total sugar content increases gradually in overwintering F1generation of the female adult, but there is no significant difference among the male adult. As far as the male and female adult in overwintering F1generation of the same geographic populations, there was not significant differences among the six geographic populations.By comparing the indexes of cold hardiness, the low latitude area like Fogang and Laibin, the cold hardiness of the populations is poorer; the high latitude area like Langfang and Yangzhou, the cold hardiness of the populations is strong,and the cold hardiness of Nanchang and Miluo in Hunan’s population in the middle. The results suggested that to some extent, cold hardiness of O. communa have an ecological plasticity, thus it has a potential to migrate to North China. |
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