Abstract Understanding the underlying processes governing host-parasitoid interactions requires sufficient knowledge of the biology and ecology of both interacting sides. Such complex data are available for only a few taxonomic groups, so explanations of evolutionary relationships are not numerous. We collected relevant published and unpublished data on interactions between ichneumonid parasitoids and their spider hosts and performed a comparative analysis of defensive traits in order to better understand their co-evolutionary history. Three primary protective strategies employed by parasitoids during the critical ontogenetic stage of pupation were identified, each involving distinct silk structures produced by the spider host: (i) the spider’s retreat, (ii) a dense three-dimensional cocoon web, and (iii) a heavily reinforced two-dimensional cocoon web. In addition, our analyses revealed that several defensive traits have evolved within 2 main lines of cocoon defense: (i) one constructed by the parasitoid, respectively, the cocoon protecting the pupa, and (ii) one constructed by the host spider, respectively, silk structures, including those resulting from the manipulation of the spider’s web-building behavior induced by the parasitoid. We further identified relationships between these traits and estimated the ancestral states of selected defensive traits. Our results support the hypotheses that the ecologies, and, particularly, the foraging strategies of spider hosts influenced the evolution of parasitoids. The phylogeny of the parasitoids was significantly congruent with spider phylogeny at the genus level, but the evidence for reciprocal adaptations in spiders is not strong. Such host-parasitoid tracking during wasp diversification is more expectable than true co-evolution.
Korenko et al. (Sun,) studied this question.