Study On The Mating Behavior And Offspring Genetic Differentiation Of Spodoptera Litur

Spodoptera litura（Fabricius）（Lepidoptera,Noctuidae）is an important pest in agriculture and forestry worldwide.It has wide distribution,wide host range,and is very high on fitness and fecundity.The host plants of S.litura include 389 species in109 families,and this pest causes serious damage on several economically important crops,including cotton,soybean,and tobacco.Chemical insecticides are currently the primary management strategy against S.litura,which makes huge problems due to resistance in larva.Insect behavior is the activity of adjusting life to better adapt to the environment,which is closely related to physiological and ecological research and pest control.To understand the optimal use of time by insects,it is necessary to know the rhythm and selection of insect behaviors.This project is going to conduct a deep study on:the mating capability of both male and female adults,the plastic response of male competition,the influence of different genetic distance and host types on mating,offspring fitness and divergence of offspring after multiple mating.Study results is believed to be of great importance to mating system,behavior pattern and evolutionary trend.Regulation strategies on mating and reproduction will provide useful information on integrated pest management of S.litura in the field.The main contents and conclusions were summarized as follows:1 Study on the fitness of different diets of S.litura1.1 Life table of S.litura fed on different dietsThere were significant differences in the developmental time,longevity and fecundity of larvae fed on tobacco,Chinese cabbage and artificial diet.The development time of population from artificial diet was 30.19 d,which was significantly shorter than population from tobacco（39.78 d）and cabbage（31.91 d）.However,the fecundity of artificial population was 1265.68,which was significantly higher than tobacco population（1058.69）and cabbage population（826.22）.There were significant differences in population parameters intrinsic rate of increase（r）,finite rate of increase（λ）,and mean generation time（T）,but no obviously differences in net reproductive rate（R₀）.1.2 Mate choice of S.litura fed on different dietsIn non-choice tests,copulation times,copulation durations,number of eggs reared significantly differed between diets.The copulation duration of cabbage population was57.26 min,which was significantly higher than tobacco population（47.53 min）and artificial diet population（44.83 min）.The cabbage group（760.76）showed the lower fecundity than tobacco（1045.55）and artificial diet group（1368.06）.The mean mating times of tobacco group was 2.46,and tobacco and artificial diet group was 1.35 and1.29,respectively.There were no significantly differences in longevity among different diets.Females showed significantly higher preference males reared on the same diet they had consumed during development,especially in the artificial diet group in which90%of female made that choice.1.3 Fitness of short-term plant induction of S.lituraThere were significant differences in the developmental time and fecundity of S.litura.When cabbage population was transferred to tobacco,the developmental time of some instars were significantly prolonged.When tobacco population was transferred to cabbage,the developmental time of some instars were significantly shortened.Fecundity of cabbage population was 1397.7,it was significantly higher than population reared on tobacco（1097.09）.Fecundity of tobacco population was 915.03.The number of eggs increased significantly when tobacco population transferred to cabbage（1312）.After short-term plant induction.There were significantly differences in the mean generation time（T）.When cabbage population transferred to tobacco,the mean generation time was significantly shortened.there were no significantly differences in other population parameters under short-term tobacco induction.However,there were significantly differences in intrinsic rate of increase（r）,finite rate of increase（λ）under short-term cabbage induction.2 Delayed mating with multiple partners decreases indexes of mating in female and male S.lituraThe delay in mating significantly decreased the number of matings and the mating success of both sexes and the male contribution to reproduction.Compared with the effect on female fecundity,the delayed mating with multiple partners had a greater effect on the male mate contribution to fecundity.The longevity of females and males increased significantly with 72 h delay in mating.when delayed mating and multiple matings occur simultaneously,multiple matings for females have a greater effect on fecundity than delayed mating,but delayed mating for males has a greater effect on fecundity than multiple matings.Linear regression analysis showed negative relations between delayed mating and fecundity and number of matings in both sexes.Thus,delayed mating with multiple partners can disrupt the mating and reproductive potential of S.litura.3 Sperm competition and plasticity response of S.lituraThe male of S.litura could produce plasticity response when facing different competitors and different environment.When mating with one female and three males,the mating duration was significantly prolonged（50.89 min）,but the fecundity was significantly decreased.When competitors were obscured by opaque,the mating duration was shortened,however,the fecundity increased significantly,to 1819.3.There was no correlation between mating duration and fecundity.Any two cues–pheromones,acoustic,visual and tactile signals to assess the presence of rivals,and then,S.litura could adjust its mating and sperm allocation strategies.Acoustic signals may play an important role in male competition,rather than touch or chemical signals.4 Study on the offspring fitness with multiple mating of S.lituraHere,we investigated the effect of parental different mating patterns（single mating,multiple mating and repeated mating）of S.litura on copulation of maternal generation,developmental,survival and fecundity of F₁ and F₂ generation.We found that there was a reversal of offspring fitness across F₂ generations of multiple mating,where fecundity F₁ generations were found to have no significantly increase,but F₂generations remarkably enhanced.Moreover,the intrinsic rate of increase,finite rate of increase and net reproductive rate of multiple mating on F₁ generations were significantly lower than single mating,but it was not obviously on F₂ generations.In addition,repeated mating had no significantly different to progeny fitness.We propose that multiple mating imposes cross-transgenerational effects,supporting the genetic benefits hypothesis and may influence the extent of evolutionary of S.litura.5 Paternity identification of multiple mating progeny of S.litura.Five microsatellite loci were selected as paternity testing system,containing CWM-2,CWM-3,CWM-4,CWM-5,CWM-6.The average of alleles number,expected heterozygosity and polymorphism content information were 4.800,0.647 and0.596,respectively.The cumulative frequency of loci met the exclusion rate in paternity test more than 99%.And 82.5%of the progeny of S.litura were able to find father,with106 had 95%confidence and 69 had 80～95%confidence.Paternity analysis was carried out with microsatellite set in 211 S.litura.During different mating treatments,the final mating males had higher paternity ratio.