周期性羽化昆虫形成机制OA北大核心CHSSCDCSTPCD

When an insect population has a long life cycle of k years(k＞1),the adult emergence will show three forms:non-periodicity,periodicity,proto-periodicity.The non-periodicity indicates that adults would emerge every year.The periodicity indicates that adults only emerge once in every k years.The proto-periodicity is a necessary period during which the non-periodical insects gradually evolve into periodical species,emergence broods of different years would show the significant differences in abundance,producing minor cohorts and dominant cohorts.In nature,it is rare that insect species display perfectly periodical emergence,whereas due to adult emergence synchronization with a relatively higher population density,the periodical insects will be more prone to cause outbreaks than related non-periodical species.In order to analyze the evolutionary process of periodic insects and provide theoretical guidance for forest pest control practice,we introduced the types and life characteristics of periodical insects in this article.Initial development of proto-periodical condition could be facilitated through climate variability of different years,natural catastrophes,dispersal into an unoccupied region,natural enemies,interspecific and intraspecific competitions.Possible mechanisms that allow periodicity evolution include life cycle prolongation,host-natural enemy interaction,low temperature driving effects,natural enemy foolhardiness-predator satiation effects,interspecific and intraspecific competitions.In forestry management practices,the tendency and extent of insect pest emergence periodicity should be evaluated in advance.When adults exhibit perfectly periodical emergence,the high efficient integrated control strategies should be adopted during the concentrated emergence year to reduce the density of only one brood below the economic threshold.When adults exhibit proto-periodical emergence,the control efforts on dominant cohorts should be strengthened,while the control frequency on small cohorts should be reduced.Field release and conservation of natural enemies should be carried out to balance the impacts of natural enemies on different developmental stages of target insect pests.As a result,the evolutionary process of periodicity through the natural enemy-host interaction would be ceased or slowed.Meanwhile,the reversion of population emergence status from proto-periodicity to non-periodicity could be gradually achieved.When adults exhibit non-periodical emergence,we should reduce the frequency of field release of specialized natural enemy species and application of control measures on specific developmental stages,and the priority should be given to select control measures that act on all developmental stages of insect pests and show no obvious differences in mortality rates,in order to avoid periodicity evolution and further outbreaks that are induced by artificial interference.