96 research outputs found

    Dry-season retreat and dietary shift of the dart-poison frog Dendrobates tinctorius (Anura: Dendrobatidae)

    Get PDF
    A precipitação sazonal afeta a dinâmica das florestas tropicais e o comportamento das espécies que fazem parte desse ecossistema. A relação positiva entre os padrões de atividade dos anfíbios e a precipitação já foi demonstrada repetidas vezes. Os membros da família Dendrobatidae, um clado de saposvenenodeflecha neotropicais, são bemconhecidos por seu uso de hábitat e comportamento durante a estação chuvosa, mas seu comportamento durante a estação seca tem recebido pouca atenção. Estudamos o uso de hábitat e a dieta do dendrobatídeo Dendrobates tinctorius na Guiana Francesa durante as estações chuvosa e seca. Ao contrário de muitos outros dendrobatídeos, D. tinctorius não mantém territórios ao longo de toda a estação chuvosa. Ambos os sexos colonizam clareiras recentemente abertas e permanecem apenas poucas semanas nessas manchas, onde os animais consomem uma grande variedade de presas, principalmente formigas, besouros, vespas, larvas de insetos e ácaros. Durante a estação seca, os animais movem-se para locais de abrigo na floresta madura, como brácteas de palmeiras e ocos de árvores. Nesse período, são menos ativos e consomem um menor número de itens alimentares; consomem menos vespas e larvas de insetos e mais cupins. Formigas constituem a presa mais comum durante as duas estações. Discutimos os efeitos das mudanças sazonais no uso de hábitat sobre o comportamento territorial dos dendrobatídeos.Seasonal rainfall affects tropical forest dynamics and behavior of species that are part of these ecosystems. The positive correlation between amphibian activity patterns and rainfall has been demonstrated repeatedly. Members of Dendrobatidae, a clade of Neotropical dartpoison frogs, are well known for their habitat use and behavior during the rainy season, but their behavior during the dry season has received little attention. We studied habitat use and diet of the dendrobatid frog Dendrobates tinctorius in French Guiana during the rainy and dry seasons. Unlike many other dendrobatid frogs, D. tinctorius does not maintain territories for the entire rainy season. Both sexes colonize recently formed canopygaps and stay in these forest patches for only a few weeks. The frogs in these patches consume a great diversity of prey, consisting of ants, beetles, wasps, insect larvae, and mites. During the dry season, frogs move to retreat sites in mature forest, such as palm bracts and tree holes. The frogs are less active and consume fewer prey items in the dry season, and they consume fewer wasps and insect larvae, but more termites. Ants are the most common prey items during both the wet and dry seasons. We discuss the effects of shifts in seasonal habitat use on the territorial behavior of dendrobatid frogs

    Hyperparasitoids exploit herbivore-induced plant volatiles during host location to assess host quality and non-host identity

    Get PDF
    Although consumers often rely on chemical information to optimize their foraging strategies, it is poorly understood how top carnivores above the third trophic level find resources in heterogeneous environments. Hyperparasitoids are a common group of organisms in the fourth trophic level that lay their eggs in or on the body of other parasitoid hosts. Such top carnivores use herbivore-induced plant volatiles (HIPVs) to find caterpillars containing parasitoid host larvae. Hyperparasitoids forage in complex environments where hosts of different quality may be present alongside non-host parasitoid species, each of which can develop in multiple herbivore species. Because both the identity of the herbivore species and its parasitization status can affect the composition of HIPV emission, hyperparasitoids encounter considerable variation in HIPVs during host location. Here, we combined laboratory and field experiments to investigate the role of HIPVs in host selection of hyperparasitoids that search for hosts in a multi-parasitoid multi-herbivore context. In a wild Brassica oleracea-based food web, the hyperparasitoid Lysibia nana preferred HIPVs emitted in response to caterpillars parasitized by the gregarious host Cotesia glomerata over the non-host Hyposoter ebeninus. However, no plant-mediated discrimination occurred between the solitary host C. rubecula and the non-host H. ebeninus. Under both laboratory and field conditions, hyperparasitoid responses were not affected by the herbivore species (Pieris brassicae or P. rapae) in which the three primary parasitoid species developed. Our study shows that HIPVs are an important source of information within multitrophic interaction networks allowing hyperparasitoids to find their preferred hosts in heterogeneous environments.</p

    A new species of Colostethus (Anura, Dendrobatidae) from French Guiana with a redescription of Colostethus beebei (Noble, 1923) from its type locality

    Get PDF
    A new species of Colostethus, long mistaken for Colostethus beebei, is described from French Guiana. The new species can be distinguished from congeners by absence of median lingual process, first finger longer than second, third finger not distinctly swollen in males, differences in tadpole morphology, coloration and pattern (e.g. absence of dorsolateral stripe), bioacoustics, and reproductive behavior. A complete redescription of Colostethus beebei plus description of its tadpole and call is provided on the basis of recently collected topotypic specimens. The range of C. beebei is restricted to the Kaieteur plateau, Pakaraima Mountains, Guyana

    Understanding insect foraging in complex habitats by comparing trophic levels : insights from specialist host-parasitoid-hyperparasitoid systems

    Get PDF
    Insects typically forage in complex habitats in which their resources are surrounded by non-resources. For herbivores, pollinators, parasitoids, and higher level predators research has focused on how specific trophic levels filter and integrate information from cues in their habitat to locate resources. However, these insights frequently build specific theory per trophic level and seldom across trophic levels. Here, we synthesize advances in understanding of insect foraging behavior in complex habitats by comparing trophic levels in specialist host-parasitoid-hyperparasitoid systems. We argue that resources may become less apparent to foraging insects when they are member of higher trophic levels and hypothesize that higher trophic level organisms require a larger number of steps in their foraging decisions. We identify important knowledge gaps of information integration strategies by insects that belong to higher trophic levels.</p

    Intraspecific variation in herbivore-induced plant volatiles influences the spatial range of plant–parasitoid interactions

    Get PDF
    Chemical information influences the behaviour of many animals, thus affecting species interactions. Many animals forage for resources that are heterogeneously distributed in space and time, and have evolved foraging behaviour that utilizes information related to these resources. Herbivore-induced plant volatiles (HIPVs), emitted by plants upon herbivore attack, provide information on herbivory to various animal species, including parasitoids. Little is known about the spatial scale at which plants attract parasitoids via HIPVs under field conditions and how intraspecific variation in HIPV emission affects this spatial scale. Here, we investigated the spatial scale of parasitoid attraction to two cabbage accessions that differ in relative preference of the parasitoid Cotesia glomerata when plants were damaged by Pieris brassicae caterpillars. Parasitoids were released in a field experiment with plants at distances of up to 60 m from the release site using intervals between plants of 10 or 20 m to assess parasitism rates over time and distance. Additionally, we observed host-location behaviour of parasitoids in detail in a semi-field tent experiment with plant spacing up to 8 m. Plant accession strongly affected successful host location in field set-ups with 10 or 20 m intervals between plants. In the semi-field set-up, plant finding success by parasitoids decreased with increasing plant spacing, differed between plant accessions, and was higher for host-infested plants than for uninfested plants. We demonstrate that parasitoids can be attracted to herbivore-infested plants over large distances (10 m or 20 m) in the field, and that stronger plant attractiveness via HIPVs increases this distance (up to at least 20 m). Our study indicates that variation in plant traits can affect attraction distance, movement patterns of parasitoids, and ultimately spatial patterns of plant–insect interactions. It is therefore important to consider plant-trait variation in HIPVs when studying animal foraging behaviour and multi-trophic interactions in a spatial context.</p

    Parasitic wasp-associated symbiont affects plant-mediated species interactions between herbivores

    Get PDF
    Microbial mutualistic symbiosis is increasingly recognised as a hidden driving force in the ecology of plant–insect interactions. Although plant-associated and herbivore-associated symbionts clearly affect interactions between plants and herbivores, the effects of symbionts associated with higher trophic levels has been largely overlooked. At the third-trophic level, parasitic wasps are a common group of insects that can inject symbiotic viruses (polydnaviruses) and venom into their herbivorous hosts to support parasitoid offspring development. Here, we show that such third-trophic level symbionts act in combination with venom to affect plant-mediated interactions by reducing colonisation of subsequent herbivore species. This ecological effect correlated with changes induced by polydnaviruses and venom in caterpillar salivary glands and in plant defence responses to herbivory. Because thousands of parasitoid species are associated with mutualistic symbiotic viruses in an intimate, specific relationship, our findings may represent a novel and widespread ecological phenomenon in plant–insect interactions.</p

    Adapted dandelions increase seed dispersal potential when they are attacked by root herbivores

    Get PDF
    Plants allow their offspring to escape unfavourable local conditions through seed dispersal. Whether plants use this strategy to escape herbivores is not well understood. Here, we explore how different Taraxacum officinale populations modify seed dispersal in response to root herbivore attack by Melolontha melolontha in the field. Root herbivore attack increases seed dispersal potential through a reduction in seed weight in populations that have evolved under high root herbivore pressure, but not in populations that have evolved under low pressure. This increase in dispersal potential is associated with reduced germination, suggesting that adapted plants trade dispersal for establishment. Analysis of vegetative growth parameters suggests that increased dispersal is not the result of stress flowering. These results suggest that root herbivory selects for genotypes that increase their dispersal ability in response to herbivore attack
    • …
    corecore