Abstract
Life‐history traits within ecological communities can be influenced by regional environmental conditions (external filters) and community‐wide density‐dependent processes (internal filters). While traits in a regional context may converge to a narrow range of values because of environmental filtering, species belonging to a guild may present contrasting traits as a means of niche differentiation, allowing coexistence whilst exploiting the same resources. To disentangle the role of external and internal filters on phenotypic diversity within ecological communities, we examined the patterns of life‐history trait variation within a guild of insect parasitoids during two successive years across three contrasted regions in relation to several ecological factors. By combining a mean‐field approach and an analysis of phenotypic variance across organizational levels (from individual to guild), we showed that the patterns of life‐history trait variation across regions are consistent with local adaptation or adaptive phenotypic plasticity while the patterns of phenotypic variation within regions suggested how coexistence modulates life‐history traits expression through niche differentiation. Within a given region, phenotypic pattern of parasitoid life‐history traits may also arise from bottom‐up effects of trophic webs: insect host species could also control parasitoid life‐history traits in nature. Our results also showed that parasitoid life‐history traits presented contrasting variation patterns according to the sampling year, suggesting temporal variations in evolutionary and ecological dynamics of parasitoid species. The application of such trait‐based studies to insect parasitoids has the potential to provide further insight on how agricultural environments contribute to differential diversification among natural enemies guilds, highlighting the main role of agricultural landscape management for organisms'responses.