Pupal size as a proxy for fat content in laboratory-reared and field-collected Drosophila species.

peer reviewe

Rising temperature reduces divergence in resource use strategies in coexisting parasitoid species.

International audienceCoexistence of species sharing the same resources is often possible if species are phylogenetically divergent in resource acquisition and allocation traits, decreasing competition between them. Developmental and life-history traits related to resource use are influenced by environmental conditions such as temperature, but thermal trait responses may differ among species. An increase in ambient temperature may, therefore, affect trait divergence within a community, and potentially species coexistence. Parasitoids are interesting models to test this hypothesis, because multiple species commonly attack the same host, and employ divergent larval and adult host use strategies. In particular, development mode (arrested or continued host growth following parasitism) has been recognized as a major organiser of parasitoid life histories. Here, we used a comparative trait-based approach to determine thermal responses of development time, body mass, egg load, metabolic rate and energy use of the coexisting Drosophila parasitoids Asobara tabida, Leptopilina heterotoma, Trichopria drosophilae and Spalangia erythromera. We compared trait values between species and development modes, and calculated trait divergence in response to temperature, using functional diversity indices. Parasitoids differed in their thermal response for dry mass, metabolic rate and lipid use throughout adult life, but only teneral lipid reserves and egg load were affected by developmental mode. Species-specific trait responses to temperature were probably determined by their adaptations in resource use (e.g. lipogenesis or ectoparasitism). Overall, trait values of parasitoid species converged at the higher temperature. Our results suggest that local effects of warming could affect host resource partitioning by reducing trait diversity in communities

Divergent life history strategies in congeneric hyperparasitoids

peer reviewedLife histories can reveal important information on the performance of individuals within their environment and how that affects evolutionary change. Major trait changes, such as trait decay or loss, may lead to pronounced differences in life history strategies when tight correlations between traits exist. Here, we show that three congeneric hyperparasitoids (Gelis agilis, Gelis acarorum and Gelis areator) that have diverged in wing development and reproductive mode employ markedly different life history strategies. Potential fecundity of Gelis sp. varied, with the wingless G. acarorum maturing a much higher number of eggs throughout life compared with the other two species. Realized lifetime fecundity, in terms of total offspring number was, however, highest for the winged G. areator. The parthenogenic G. agilis invests its resources solely in females, whilst the sexually reproducing species both invested heavily in males to reduce competitive pressures for their female offspring. Longevity also differed between species, as did the direction of the reproduction-longevity trade-off, where reproduction is heavily traded off against longevity only in the asexual G. agilis. Resting metabolic rates also differed between the winged and wingless species, with the highest metabolic rate observed in the winged G. areator. Overall, these geline hyperparasitoids showed considerable divergence in life history strategies, both in terms of timing and investment patterns. Major trait & Bertanne Visse

Small-scale spatial resource partitioning in a hyperparasitoid community

peer reviewe

Common Practice Solvent Extraction Does not Reflect Actual Emission of a Sex Pheromone During Butterfly Courtship

Olfactory communication can be of critical importance for mate choice decisions. Lepidoptera are key model systems for understanding olfactory communication, particularly considering sex pheromone signaling in the context of sexual selection. Solvent extraction or rinsing of pheromone-producing structures is a widespread method for quantifying sex pheromones, but such measures reflect what is stored and may not represent what is actually emitted by an individual during courtship. Here, we address this point for the first time by quantifying the components of the male sex pheromone (MSP) of interacting Bicyclus anynana butterflies, a species for which much information is available onthe role played by MSPs in affecting mating success. Using headspace sampling during courtship and solvent extraction after completion of experiments using the same males, we were able to track individual traits. Our results show that solvent extracts do not reflect quantities of MSP components emitted by live butterflies. We further show that MSP amounts obtained using headspace sampling correlated with male mating success, but solvent extracts did not. Our results further strongly suggest that males actively control MSP emission when faced with increased male-male competition. Common practice solvent extracts may thus not serve as an adequate proxy for male sex pheromone signaling as they are perceived by choosy females. Our study serves as a proof of principle that quantification of male sex pheromone components depends on the method of collection, which could apply to many other insects using short-range chemical signals. This affects our understanding of how sexual selection shapes the evolution of sexually-selected chemical traits

Mosaic Evolution of Molecular Pathways for Sex Pheromone Communication in a Butterfly

peer reviewe

Multi-gene and lineage comparative assessment of the strength of selection in Hymenoptera

Genetic variation is the raw material for selection to act upon and the amount of genetic variation present within a population is a pivotal determinant of a population’s evolutionary potential. A large effective population size, i.e., the ideal number of individuals experiencing the same amount of genetic drift and inbreeding as an actual population, Ne (Wright 1931, Crow 1954), thus increases the probability of long-term survival of a population

The importance of fat accumulation and reserves for insect overwintering.

peer reviewedWinter is a challenging season for ectothermic species such as insects. In addition to thermal stress imposed by cold temperatures, food scarcity during winter can lead to starvation and energy drain. In preparation for winter, most insects accumulate lipid (fat) reserves, which are the principal source of energetic fuel during overwintering. In this review, we highlight the most recent literature on lipid metabolism in response to cold. We first discuss how lipid metabolism is affected by biotic and abiotic environmental changes in preparation for winter. We then highlight how lipid dynamics are affected during winter, including physiological and (epi)genetic mechanisms. We end our review emphasizing the importance of remaining fat reserves in spring and how climate change can negatively impact lipid metabolism and fitness

Incestuous insects in nature despite occasional fitness costs

International audienceA recommendation based on reviews by two anonymous reviewers of Collet M, Amat I, Sauzet S, Auguste A, Fauvergue X, Mouton L, Desouhant E. 2018. Insects and incest: sib -mating tolerance in natural populations of a parasitoid wasp. bioRxiv 169268, ver. 6 peer -reviewed by Peer community In Evolutionary Biology