Significant resource niche overlap between competing parasitoids does not prevent their successful co‐existence

Abstract Different species that exploit the same resources can sometimes co‐exist in the same habitat through resource sharing. For example, if resources are superabundant, then they can be easily partitioned interspecifically among different individuals. However, when resources are scarce, theory predicts that one species will competitively exclude the other if the life cycles of both species overlap spatially and temporally. Here, we studied intrinsic competition between two sympatric gregarious parasitoids, Oomyzus scaposus and O. spiraculus , when developing in the same host individual, that is, larvae of the ladybird Coccinella septempunctata . When hosts were parasitized by one species only, the larvae consumed almost the entire host during their development, leaving nothing available for interspecific competitors. However, in hosts parasitized by both species at different time intervals, resources were partitioned among them, allowing both species to successfully develop and emerge as adults. Nevertheless, O. scaposus was a marginally superior competitor in multiparasitized hosts. This is, as far as we know, the first example of interspecific resource sharing among parasitoids whose larvae consume virtually all host tissues during development. Given that this is an enormous group of insects that exhibit extreme phylogenetic complexity in the expression of traits, these results illustrate how two parasitoid species co‐exist on highly limited resources. Read the free Plain Language Summary for this article on the Journal blog.