Effects of Intraspecific Competition and Host-Parasitoid Developmental Timing on Foraging Behaviour of a Parasitoid Wasp

In a context where hosts are distributed in patches and susceptible to parasitism for a limited time, female parasitoids foraging for hosts might experience intraspecific competition. We investigated the effects of host and parasitoid developmental stage and intraspecific competition among foraging females on host-searching behaviour in the parasitoid wasp Hyposoter horticola. We found that H. horticola females have a pre-reproductive adult stage during which their eggs are not mature yet and they forage very little for hosts. The wasps foraged for hosts more once they were mature. Behavioural experiments showed that wasps’ foraging activity also increased as host eggs aged and became susceptible to parasitism, and as competition among foraging wasps increased.Peer reviewe

Preface

Non peer reviewe

The roles of trophic interactions, competition and landscape in determining metacommunity structure of a seed-feeding weevil and its parasitoids

Community composition is determined by attributes of the environment, individual species, and interactions among species. We studied the distributions of a seed weevil and its parasitoid and hyperparasitoid wasps in a fragmented landscape. The occurrence of the weevil was independent of the measured attributes of the landscape (patch connectivity and resource availability). However, between habitat-patch networks, weevil density decreased with increasing parasitism, suggesting top-down control, especially in the north. Parasitism was mostly due to a specialist and a generalist that appeared to compete strongly. This competitive interaction was strongest at high patch-connectivity, perhaps due to a trade-off of local competitive ability and dispersal. Finally, the abundance of the generalist hyperparasitoid was unrelated to landscape or host-species abundance. The snapshot presented by these data can best be explained by top-down effects, interactions among species, host ranges, and patch con guration in the landscape, but not by local host-plant abundance.Peer reviewe

Variation in a host–parasitoid interaction across independent populations

Abstract: Antagonistic relationships between parasitoids and their insect hosts involve multiple traits and are shaped by their ecological and evolutionary context. The parasitoid wasp Cotesia melitaearum and its host butterfly Melitaea cinxia occur in several locations around the Baltic sea, with differences in landscape structure, population sizes and the histories of the populations. We compared the virulence of the parasitoid and the susceptibility of the host from five populations in a reciprocal transplant-style experiment using the progeny of five independent host and parasitoid individuals from each population. The host populations showed significant differences in the rate of encapsulation and parasitoid development rate. The parasitoid populations differed in brood size, development rate, pupal size and adult longevity. Some trait differences depended on specific host-parasitoid combinations, but neither species performed systematically better or worse in experiments involving local versus non-local populations of the other species. Furthermore, individuals from host populations with the most recent common ancestry did not perform alike, and there was no negative effect due to a history of inbreeding in the parasitoid. The complex pattern of variation in the traits related to the vulnerability of the host and the ability of the parasitoid to exploit the host may reflect multiple functions of the traits that would hinder simple local adaptation.Peer reviewe

The more the merrier : Conspecific density improves performance of gregarious larvae and reduces susceptibility to a pupal parasitoid

Aggregation can confer advantages in animal foraging, defense, and thermoregulation. There is a tight connection between the evolution of insect sociality and a highly effective immune system, presumably to inhibit rapid disease spread in a crowded environment. This connection is less evident for animals that spend only part of their life cycle in a social environment, such as noneusocial gregarious insects. Our aim was to elucidate the effects of group living by the gregarious larvae of the Glanville fritillary butterfly with respect to individual performance, immunity, and susceptibility to a parasitoid. We were also interested in the role of family relative to common postdiapause environment in shaping life-history traits. Larvae were reared at high or low density and then exposed to the pupal parasitoid wasp Pteromalus apum, either in presence or absence of a previous immune challenge that was used to measure the encapsulation immune response. Surviving adult butterflies were further tested for immunity. The wasp offspring from successfully parasitized butterfly pupae were counted and their brood sex ratios assessed. Larvae reared at high density grew larger and faster than those at low density. Despite high mortality due to parasitism, survival was greater among individuals with high pupal immunity in both density treatments. Moreover, butterfly pupae reared at high density were able to kill a larger fraction of individuals in the parasitoid broods, although this did not increase survival of the host. Finally, a larger proportion of variation observed in most of the traits was explained by butterfly family than by common postdiapause rearing environment, except for adult survival and immunity, for which this pattern was reversed. This gregarious butterfly clearly benefits from high conspecific density in terms of developmental performance and its ability to fight a parasitoid. These positive effects may be driven by cooperative interactions during feeding.Peer reviewe

Attraction of Melitaea cinxia butterflies to previously-attacked hosts : a likely complement to known Allee effects?

Clumped distributions of herbivorous insect eggs often result from independent assess- ments of individual plants by different ovipositing females. Here we ask whether, in addition, plants might be rendered more or less attractive to ovipositing Melitaea cinxia butter ies by presence of conspeci c eggs and/or by prior larval attack. Both eggs and larval damage rendered Veronica spicata plants signi cantly more accept- able; the effect of eggs was particularly strong. Larval damage caused a marginally signi cant increase in acceptability of Plantago lanceolata, but there was no trend for an effect of eggs on this host. Variable oviposition preferences of Melitaeine butter ies are known to drive their metapopulation dynamics by affecting rates of emigration and patch colonization. Therefore variable host acceptability, as documented here, should do likewise, reducing emigration rates at high population densities where V. spicata is present in the landscape and complementing Allee effects that are already known in this system.Peer reviewe

Mbya Guarani e a paisagem florestal como ambiente educativo

A partir do convívio em duas comunidades Mbya Guarani, sendo uma delas a Tekoá Kuaray Rese, Aldeia Sol Nascente, em Osório-RS, e a outra Tekoá Guyrai Nhendu, Aldeia Som dos Pássaros, em Maquiné-RS, este trabalho de Conclusão de Curso trata do cotidiano destas comunidades e a perspectiva de uma educação que é intrínseca a esse tempo. A espiritualidade, a memória e a relação das pessoas com as plantas são alguns elementos definidores da educação indígena, ressoando na percepção que os guarani têm sobre a instituição escolar. Desde a chegada do colonizador, os povos tradicionais vêm sendo educados, sempre na tentativa de incluí-los no modo de pensar hegemônico e institucional do ocidente. Esta pesquisa buscou refletir, através de conversas com lideranças indígenas, de que modo, nos últimos anos, empoderados de pensamento crítico e valorizando seu modo de educação, buscaram aproveitar o espaço da escola para o fortalecimento de sua cultura ancestral. O reconhecimento das plantas nativas e seus diversos usos objetivos ou simbólicos, pelas comunidades Mbya Guarani, são essenciais para manutenção e afirmação da cultura. Com as demarcações de terra, que limitam o caminhar guarani, e com a descaracterização florestal que as matas vêm sofrendo, a agroecologia pode ser usada como estratégia de resgate e manutenção cultural. O cultivo em viveiro e plantio de árvores nativas surgem como meio de recomposição da paisagem guarani, além de ser um espaço vivo do compartilhamento de saberes tradicionais. A partir disso e transformando a lógica do ensino escolar, considera-se que o pensamento sistêmico em harmonia com a natureza, deveria ser tido como lição às pessoas não indígenas na busca de uma mudança de paradigmas socioambientais

Host specialization by Cotesia wasps (Hymenoptera: Braconidae) parasitizing species-rich Melitaeini (Lepidoptera: Nymphalidae) communities in north-eastern Spain

In order to investigate parasitoids of the genus Cotesia (Hymenoptera: Braconidae), larvae of a speciose group of butterflies, the tribe Melitaeini (Lepidoptera: Nymphalidae), were collected from several sites in Catalonia, northern Spain, a region that harbours ten out of the 20 European species of Melitaeini. New information on the natural history of the butterflies is presented, and the structure of their communities and patterns of larval parasitism are described. On the basis of mtDNA sequence data (COI gene), microsatellite data (ten loci) and behavioural experiments, we recognize seven biologically distinct species of Cotesia parasitizing the Melitaeini communities within this relatively small geographical area. In particular, the notional species C. melitaearum and C. acuminata each represents a series of cryptic species with narrow host associations. The possibility of direct competition among the parasitoids and/or indirect interactions between butterflies mediated by Cotesia parasitoids is explored

Differential Performance of a Specialist and Two Generalist Herbivores and Their Parasitoids on Plantago lanceolata

The ability to cope with plant defense chemicals differs between specialist and generalist species. In this study, we examined the effects of the concentration of the two main iridoid glycosides (IGs) in Plantago lanceolata, aucubin and catalpol, on the performance of a specialist and two generalist herbivores and their respective endoparasitoids. Development of the specialist herbivore Melitaea cinxia was unaffected by the total leaf IG concentration in its host plant. By contrast, the generalist herbivores Spodoptera exigua and Chrysodeixis chalcites showed delayed larval and pupal development on plant genotypes with high leaf IG concentrations, respectively. This result is in line with the idea that specialist herbivores are better adapted to allelochemicals in host plants on which they are specialized. Melitaea cinxia experienced less post-diapause larval and pupal mortality on its local Finnish P. lanceolata than on Dutch genotypes. This could not be explained by differences in IG profiles, suggesting that M. cinxia has adapted in response to attributes of its local host plants other than to IG chemistry. Development of the specialist parasitoid Cotesia melitaearum was unaffected by IG variation in the diet of its host M. cinxia, a response that was concordant with that of its host. By contrast, the development time responses of the generalist parasitoids Hyposoter didymator and Cotesia marginiventris differed from those of their generalist hosts, S. exigua and C. chalcites. While their hosts developed slowly on high-IG genotypes, development time of H. didymator was unaffected. Cotesia marginiventris actually developed faster on hosts fed high-IG genotypes, although they then had short adult longevity. The faster development of C. marginiventris on hosts that ate high-IG genotypes is in line with the “immunocompromized host” hypothesis, emphasizing the potential negative effects of toxic allelochemicals on the host’s immune response