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Despite the popularity of stable isotope analysis (Carbon and Nitrogen), the drivers of species isotopic niches and their consequences on food web functioning remained poorly described, especially in estuaries. Here, we hypothesised that species niche characteristics are influenced by ecosystem hydro-morphological features and the functional structure of fish assemblages. The trophic niches of four fish species (Dicentrarchus labrax, Pomatoschistus minutus, Sprattus and Platichthys flesus) and overlap between them were compared during two consecutive autumns in eight estuarine ecosystems of the northeast Atlantic Ocean. Our findings demonstrated a relative steadiness of trophic positions of fish in estuaries, despite a high level of interspecific variability. The seabass generally occupied the higher trophic position, followed by the sand goby, while the flounder and sprat were at the lowest position in the food web. Species isotopic niches and overlap were mediated by some estuarine features, including estuary size and intertidal extent, but also by biotic interactions at the intra- and inter-specific levels, as reflected by the influence of fish abundance and functional diversity metrics. Our results support the statement that the intertidal area is a pivotal factor in regulating trophic interactions, by promoting niche partitioning and diversification of trophic resources between species. Moreover, niche size and dietary divergence of species decreased with increasing regularity of trophic strategies within assemblages, suggesting that species occupied more restricted trophic niches when they were less subjected to competition for the same food resources. These findings emphasize the importance of local conditions and the functional composition of assemblages in modulating the trophic resources consumed by fish in estuarine environments. [Display omitted] • Trophic niches of four fishes were investigated across eight estuaries. • Species isotopic niches were influenced by functional diversity of assemblages. • Niche size and divergence decreased with functional divergence and evenness. • Intra- and inter-specific interactions affect species niches and overlap. • Intertidal area promote niche partitioning and diversification of trophic resources. [ABSTRACT FROM AUTHOR]

As a result of female remating, sexual selection can operate both before and after copulation, yet studies of sexual selection on males tend to focus on individual episodes of reproduction in isolation. We examined whether different episodes of sexual selection are related in the sperm-polymorphic Indian meal moth, Plodia interpunctella. We found that the ability to mate with nonvirgin females determined male precopulatory reproductive success. In addition, males that transferred more sperm during their first mating were better at both sperm competition and reducing females' propensity to remate, suggesting that sperm production and transfer are key determinants of reproductive success in this species. However, no relationships were found between traits contributing to pre- versus postcopulatory sexual selection. Our results illustrate the importance of considering variation in all aspects of male reproductive success when examining sexual selection. [ABSTRACT FROM AUTHOR]

Kin recognition, defined as the ability to differentiate genetically related from unrelated individuals, plays a key role in a range of biological processes, from mate choice to altruistic behaviours, but kin-based altruism may be overridden by competition for resources. We explored kin recognition in a gregarious parasitoid wasp, Goniozus legneri, in which adult female–female contests for hosts occur. Contest behaviour was less aggressive when competitors were more closely related and also when females had developed on the same host (in nature, broodmates will almost always be siblings). Goniozus legneri appears to be the only parasitoid species utilizing both genetically based (phenotype matching) and environmentally based (familiarity) mechanisms of phenotypic kin discrimination. While perceived resource value affects aggression in Goniozus, resource competition did not completely override kin recognition effects. [Copyright &y& Elsevier]