Habitat determinants of the taxonomic and functional diversity of parasitoid wasps

Abstract

Parasitoid wasps (Hymenoptera) are a highly diverse component of terrestrial habitats, yet very little is known about how their community structure and functional diversity is influenced by habitat variables. Parasitoids were sampled using Malaise traps in early and late summer across ten forest sites in the Waitakere Ranges, New Zealand. At each trap, a range of local habitat variables were measured in a 20 × 20 m plot and landscape cover data were obtained for a 2-km radius. Species from two families, Ichneumonidae and Braconidae, were identified using morphological and molecular methods. Functional groups (idiobiosis, koinobiosis), key life history traits (endoparasitism, ectoparasitism, host taxa), and morphological traits (ovipositor length, body size) were measured to calculate functional diversity indices. The abundance, species richness, composition, and functional groups of parasitoids were chiefly influenced by vegetation type, plant diversity, coarse woody debris, and seasonal sampling. However, different taxa showed different patterns to habitat variables. Functional diversity measures were strongly linked to vegetation type. Kauri conifer forest was found to support a specialised parasitoid community, with lower abundance and species richness than broadleaved forest, but with higher functional evenness and high functional dispersion; indicating a community of co-existing species with a high utilisation of resources. The lack of congruence in the habitat relationships of different parasitoid groups highlights that preservation of a wide range of different forest habitats is required to adequately conserve parasitoid diversity.