Vegetation variables influencing parasitoid diversity in a Mediterranean landscape

• Ichneumonidae diversity might be enhanced when tree layer is not dense. • A high plant richness might disfavor the presence of specialist parasitoids. • A well developed herbaceous layer seemed to favor generalist parasitoids. • Seasons influenced on Ichneumonidae species assemblages. The structural complexity of vegetation may favor the parasitoid diversity of a habitat by increasing the number of potential niches for their hosts and for themselves, but how vegetation structural variables are contributing to diversity is still uncertain. Here we aimed to determine the vegetation variables that influence diversity, abundance, richness and assemblage composition of Darwin wasps (Hymenoptera, Ichneumonidae). We considered the life strategies (idiobiont/koinobiont, and ecto/endoparasitoids) and trophic guilds of Ichneumonidae, and how this relationship is shifted in different temporary seasons. We evaluated several vegetation structural variables (height, cover, species richness, life-forms diversity) of the tree, shrub and herbaceous layers, in five different habitats along a structure complexity gradient of vegetation in a protected area of Central Spain, in two seasons: spring and autumn. Vegetation variables were correlated to Ichneumonidae variables. A non-metric multidimensional scaling (NMDS) was conducted to identify patterns of Ichneumonidae species composition in relation to vegetation variables measured in two seasons. Plant richness negatively affected the abundance of koinobionts and endoparasitoids, whilst a greater cover of the herbaceous layer supported a greater abundance of idiobionts and ectoparasitoids. Ichneumonidae assemblages varied significantly regarding habitats but also differed among the two seasons. The structural complexity of plant communities is not sufficient to predict parasitoid diversity, but some vegetation traits, such as a well-developed herbaceous layer, can be considered when planning conservation management strategies to keep a high parasitoid diversity. Other variables, not only at habitat but also at landscape level, should be considered.