Maternal Effects On Offspring Development,reproduction And Flight Performance In The Oriental Armyworm Mythimna Separata:Consequence Of Temperature,Larval Density And Flight

The oriental armyworm,Mythimna separata(Lepidoptera: Noctuidae),a typical long-distance migratory polyphagous insect pest of grain crops in China and other Asian countries,causing huge crop production and economic losses nationwide annually;with multiple generations per year.Cross-generational effects refer to non-genetic influences of the parental phenotype or environment on offspring phenotypes,these effects may cause life-history traits to differing over the season.A low parental temperature resulted in female offspring that developed slower at low developmental temperature compared with females whose parents were reared at high temperature.Also,females whose parents were reared at low temperature have longer pre-oviposition period than females whose parents were reared at high temperature.Furthermore,females whose parents were reared at low temperature were heavier and more fecund and had weaker flight abilities than females whose parents were reared at high temperature.In addition to these cross-generational effects,females had less fecundity and poorer flight abilities at low than at high ambient adult temperature no what matter they developed at high or low temperatures.Our findings demonstrate a balanced benefit of parental temperature on offspring performance,as well as between-and within-generation effects of acclimation to temperature.In cooler environments,the offspring generation is expected to develop more slowly and to comprise more fecund but weaker flight females.However,in warmer environment,the offspring generation develops more rapidly,stronger flight but less fecundity.By producing phenotypes that are adaptive to the conditions inducing them as well as heritable,cross-generational plasticity can influence the evolutionary trajectory of populations.The potential for short-term acclimation to low or high temperature may allow expanding insect populations to better cope with novel environments by flight or inhabit local place by reproduction and may help to explain the phase change of the this kind of migratory species.Parental rearing density experience can impose phenotypic changes on offspring life history traits.The development time is shortened after parental high density rearing and pupal mass significantly dropped at daughters stressed conditions.Lifetime egg production was significantly affected by parental larval density;number of eggs of offspring developed in moderate density whose parents from moderate density was higher as compared to other two density parents,however,number of eggs of offspring developed in high density whose parents from low density was higher as compared to other two density parents.Furthermore,parental larval density had a significant effect on the flight potential,including flight duration,flight distance,flight velocity,and longest flight duration.Tethered flight techniques were used to investigate the flight potential of 1-d adult old daughters from parents reared at different larval densities.Offspring whose parents raised at moderate density displayed greatest and daughters whose mothers raised at isolation had poorest flight capacity,relative to high density daughters.Parental larval density had a significant effect on length of the pre-oviposition period,daughters with longer pre-ovopistion period usually showed greater and positive correlation with flight performance.Daughters whose parents reared at low density had a longer lifespan than other density regimes.The characteristics of progeny can be influenced by the crowding or isolation conditions experienced by the parents.These results suggest that parental larval density applies a significant influence on offspring considered life history traits in M.separata.Flight-induced changes in maternal egg provisioning had direct consequences for offspring growth and survival across each life stage from egg to adulthood.This study demonstrates that a change in maternal provisioning as a result of increased flight during the oviposition period has the potential to exert non-genetic fitness effects.In addition,the results provided knowledge about different temperature levels for survival and their effects on next generation,which could help us to monitor and forecast accurately the occurrence of M.separata.This could have important consequences for population dynamics this noxious insect pest.