We assessed the adaptiveness of refraining from infanticidal probing at the third attack under triple parasitism in the parasitoid Echthrodelphaxfairchildii Perkins, by comparing fitness returns from the third attack ...We assessed the adaptiveness of refraining from infanticidal probing at the third attack under triple parasitism in the parasitoid Echthrodelphaxfairchildii Perkins, by comparing fitness returns from the third attack with and without probing. Fitness returns were assessed in terms of the survival rate, mean developmental time, and mean adult head width of the progenies. Not probing was maladaptive under triple parasitism with oviposition intervals of 1/24 and 24/24 hours （where the numbers before and after the slash refer to the first-to-second and second-to-third oviposition intervals, respectively）, although no significant difference was detected in fitness returns for oviposition intervals of 24/1 hours. We suggest that the cost of probing （especially the decrease in the chance of future ovipositions） is a reason for the seemingly maladaptive absence of probing.展开更多
Natal rearing experience of animals may affect their behaviors,such as habitat selection and oviposition decision.As part of the overall fitness of insect parasitoids, successful host discrimination (distinguishing pa...Natal rearing experience of animals may affect their behaviors,such as habitat selection and oviposition decision.As part of the overall fitness of insect parasitoids, successful host discrimination (distinguishing parasitized hosts from unparasitized hosts) is of paramount importance.In this study we examined whether and how parasitoids' natal rearing experience would affect their host discrimination ability according to host availability.We established separate colonies ofAphidius gifuensis Ashmead by continual rearing on two hosts,Sitobion avenae E and Myzuspersicae (Suzler),and quantified self superparasitism and self superparasitism versus parasitism ratio for the four:combinations ofparasitoid colonies and host species (S.aveane and M.persicae)at four host densities (30,50,100 or 150 per plant).Results showed that self superparasitism ofM.persicae by A.gifuensis reared on S.avenae was significantly higher than by those reared on M.persicae,no matter whether the host densities were 30,50,100 or 150.Aphidius gifuensis reared on M.persicae significantly superparasitized more S.avenae than those reared on S.aveane only when host density was 30.Self superparasitism versus parasitism ratio of A.gifuensis from both colonies was always lower on natal hosts than on new hosts,and the difference was more pronounced as the host density decreased.These results suggested that natal rearing effects is important on host discrimination and oviposition decision of the parasitoid A.gifuensis.These effects promoted the parasitoid's host adaptation and made them confer greater fitness.展开更多
Organisms often live in unpredictable environments and have to adopt life history strategies that optimize their fitness under these conditions.According to bet-hedging theory,individuals can reduce variation in fitne...Organisms often live in unpredictable environments and have to adopt life history strategies that optimize their fitness under these conditions.According to bet-hedging theory,individuals can reduce variation in fitness outcomes by investing in different strategies at the same time.For arthropods,facultative summer diapause enables survival during dry and hot periods of the year,and can be triggered by a decrease in resource abundance. However,the effect of resource depletion on diapause induction has never been disentangled from the effect of the perception of the presence of competitors.Using two solitary parasitoid species of cereal aphids as a model system,Aphidius avenae (Haliday)and Aphidius rhopalosiphi (De Stefani-Perez)(Hymenoptera:Braconidae),we tested whether (i)low absolute host density and/or (ii)high levels of parasitoid females'competition lead to maternal-induced summer diapause in parasitoid offspring.Under summer-like climatic conditions,emerging parasitoid females were (i)reared alone and exposed to different host densities (from 5 to 130 aphids),or (ii)reared together with competing females (from 2 to 20 females)and then exposed individually to 50 aphids.For both parasitoid species, low aphid densities did not induce summer diapause.However,the incidence of summer diapause increased up to a maximum of 11% with increasing levels of competition expe rienced by female parasitoids.More than 60% of the females produced both diapausing and nondiapausing offspring after being kept at the two highest competition densities. Such a "spreading-the-risk"strategy has likely evolved to optimize parasitoid fitness by preventing the following generation from exposure to low populations of suitable hosts and high mortality from superparasitism.These results provide the first experimental evidence of direct maternal competition-induced diapause in insects,and may change the way we apprehend the evolution of arthropod seasonal ecology,by considering intraspecific competition.展开更多
文摘We assessed the adaptiveness of refraining from infanticidal probing at the third attack under triple parasitism in the parasitoid Echthrodelphaxfairchildii Perkins, by comparing fitness returns from the third attack with and without probing. Fitness returns were assessed in terms of the survival rate, mean developmental time, and mean adult head width of the progenies. Not probing was maladaptive under triple parasitism with oviposition intervals of 1/24 and 24/24 hours （where the numbers before and after the slash refer to the first-to-second and second-to-third oviposition intervals, respectively）, although no significant difference was detected in fitness returns for oviposition intervals of 24/1 hours. We suggest that the cost of probing （especially the decrease in the chance of future ovipositions） is a reason for the seemingly maladaptive absence of probing.
基金the National Basic Research Program of Ministry of Science and Technology,China(973 Program,2012CB114105)National Natural Science Foundation of China (31272089)China Agriculture Research System (CARS一25一B一06).
文摘Natal rearing experience of animals may affect their behaviors,such as habitat selection and oviposition decision.As part of the overall fitness of insect parasitoids, successful host discrimination (distinguishing parasitized hosts from unparasitized hosts) is of paramount importance.In this study we examined whether and how parasitoids' natal rearing experience would affect their host discrimination ability according to host availability.We established separate colonies ofAphidius gifuensis Ashmead by continual rearing on two hosts,Sitobion avenae E and Myzuspersicae (Suzler),and quantified self superparasitism and self superparasitism versus parasitism ratio for the four:combinations ofparasitoid colonies and host species (S.aveane and M.persicae)at four host densities (30,50,100 or 150 per plant).Results showed that self superparasitism ofM.persicae by A.gifuensis reared on S.avenae was significantly higher than by those reared on M.persicae,no matter whether the host densities were 30,50,100 or 150.Aphidius gifuensis reared on M.persicae significantly superparasitized more S.avenae than those reared on S.aveane only when host density was 30.Self superparasitism versus parasitism ratio of A.gifuensis from both colonies was always lower on natal hosts than on new hosts,and the difference was more pronounced as the host density decreased.These results suggested that natal rearing effects is important on host discrimination and oviposition decision of the parasitoid A.gifuensis.These effects promoted the parasitoid's host adaptation and made them confer greater fitness.
文摘Organisms often live in unpredictable environments and have to adopt life history strategies that optimize their fitness under these conditions.According to bet-hedging theory,individuals can reduce variation in fitness outcomes by investing in different strategies at the same time.For arthropods,facultative summer diapause enables survival during dry and hot periods of the year,and can be triggered by a decrease in resource abundance. However,the effect of resource depletion on diapause induction has never been disentangled from the effect of the perception of the presence of competitors.Using two solitary parasitoid species of cereal aphids as a model system,Aphidius avenae (Haliday)and Aphidius rhopalosiphi (De Stefani-Perez)(Hymenoptera:Braconidae),we tested whether (i)low absolute host density and/or (ii)high levels of parasitoid females'competition lead to maternal-induced summer diapause in parasitoid offspring.Under summer-like climatic conditions,emerging parasitoid females were (i)reared alone and exposed to different host densities (from 5 to 130 aphids),or (ii)reared together with competing females (from 2 to 20 females)and then exposed individually to 50 aphids.For both parasitoid species, low aphid densities did not induce summer diapause.However,the incidence of summer diapause increased up to a maximum of 11% with increasing levels of competition expe rienced by female parasitoids.More than 60% of the females produced both diapausing and nondiapausing offspring after being kept at the two highest competition densities. Such a "spreading-the-risk"strategy has likely evolved to optimize parasitoid fitness by preventing the following generation from exposure to low populations of suitable hosts and high mortality from superparasitism.These results provide the first experimental evidence of direct maternal competition-induced diapause in insects,and may change the way we apprehend the evolution of arthropod seasonal ecology,by considering intraspecific competition.
