Australian Journal of Entomology (2006) 45, 176–184 © 2006 The Authors Journal compilation © 2006 Australian Entomological Society doi:10.1111/j.1440-6055.2006.00519.x Blackwell Publishing AsiaMelbourne, AustraliaAENAustralian Journal of Entomology1326-67562005 Australian Entomological Society? 2006451176184Original ArticleParasitic wasps associated with non-crop plants C J Stephens et al. *Present address: Centre for Evolutionary Biology and Biodiversity, School of Earth and Environmental Sciences, The University of Adelaide, SA 5005, Australia (email: claire.stephens@adelaide.edu.au). † Present address: CSIRO Entomology, Indooroopilly, Qld 4068, Australia. Parasitic wasp assemblages associated with native and weedy plant species in an agricultural landscape Claire J Stephens, 1 * Nancy A Schellhorn, 1† Glenys M Wood 1 and Andrew D Austin 2 1 South Australian Research and Development Institute, Entomology Unit, Urrbrae, SA 5064, Australia. 2 Centre for Evolutionary Biology and Biodiversity, School of Earth and Environmental Sciences, The University of Adelaide, SA 5005, Australia. Abstract The establishment and maintenance of suitable habitat on-farm or in the surrounding landscape can enhance the survival of beneficial parasitic Hymenoptera, thus improving the control of pest species. Both endemic and weedy non-crop plant species across a highly modified agricultural landscape supported species-rich and abundant parasitic wasp assemblages with diverse biology and host asso- ciations. It was also shown that isolated, recently planted, single-species stands of plants can rapidly accumulate diverse assemblages of parasitoids. Chalcidoidea was the most species-rich and abundant group, egg and larval parasitoids were the most speciose and abundant guilds, and parasitoids of herbivorous insects feeding on and inside plant tissue were the most species-rich and abundant functional groups. The hymenopteran assemblages associated with the majority of plant species were dominated by three parasitoid species: a Trichogrammatidae, a Scelionidae (Telenomus sp.) and a Eulophidae (Ceranisus sp.), all genera that contain many important biocontrol agents of pest Lepi- doptera, Hemiptera and Thysanoptera. Results show that both native and weedy plant species may potentially provide an important reservoir of mobile parasitic wasps of benefit to crop protection. Key words functional groups, guilds, horticulture, parasitic Hymenoptera, revegetation, weeds. INTRODUCTION Parasitic Hymenoptera are a major component of most terres- trial ecosystems contributing up to 20% of all insect species, with estimates of over 31 000 species in Australia alone (LaSalle & Gauld 1993; Yeates et al. 2003). Parasitic wasps are regarded as one of the main factors regulating population dynamics of phytophagous insects and the large diversity of phytophagous hosts utilised (Hawkins 1993) illustrates their significance in many habitats via interactions with other arthropods. The evolution of specific parasitoid–host associa- tions and the ability to regulate host populations have resulted in parasitic wasps playing a key role in the biological control of agricultural pests (LaSalle 1993). Most agricultural crops do not have sufficient resources to maintain high levels of natural enemies (Schellhorn et al. 2000). Therefore, the establishment and maintenance of more suitable habitat on-farm or in the surrounding landscape can enhance the survival of both introduced and naturally occur- ring parasitic Hymenoptera and thus improve the biological control of pest species (Gurr et al. 2004). Non-crop vegetation may provide parasitoids with overwintering sites, refuge from disturbance such as crop harvesting, adult food sources such as nectar, access to alternative hosts, and can result in the build-up of parasitoid populations over time (Schellhorn et al. 2000; Tscharntke 2000). Remnant vegetation is sometimes preserved and non-crop plants (both exotic and native) grown adjacent to agricultural production for these reasons. The veg- etation community surrounding particular crops can influence parasitoid diversity, abundance and seasonality (Altieri et al. 1993); however, there is limited information about the para- sitic wasp species assemblages associated with vegetation sur- rounding agricultural crops in Australia, particularly remnant and newly planted native species. To understand the role that non-crop vegetation may play in supporting parasitic Hymenoptera, either as habitat or as hosts, we surveyed native and exotic plants on farms and surrounding landscapes. Below we describe the parasitic hymenopteran assemblages from intensive horticultural pro- duction associated with four species of local native plants occurring as either newly planted or remnant vegetation. As weeds are often the most common sources of nectar and pollen of non-crop plants for natural enemies in agricultural systems (Schellhorn et al. 2000), two species of abundant exotic weeds were also sampled. We compare parasitic wasp assemblages (abundance, species richness, guild structure and functional groups) associated with each plant species, discuss the domi- nant species recorded and, based on biology and host associ-