Diversity and host specificity of Psylloidea (Hemiptera) inhabiting box mistletoe, Amyema miquelii (Loranthaceae) and three of its host Eucalyptus species Anna E Burns, 1 * Gary S Taylor, 2 David M Watson 1 and Saul A Cunningham 3 1 School of Environmental Sciences and Institute for Land, Water and Society, Charles Sturt University, PO Box 789, Albury, NSW 2640, Australia. 2 Australian Centre for Evolutionary Biology and Biodiversity, School of Earth and Environmental Sciences, The University of Adelaide, Adelaide, SA 5005, Australia. 3 CSIRO Ecosystem Sciences, Black Mountain, ACT 2601, Australia. Abstract This study is the first direct comparison of the diversity of phytophagous insects associated with a parasitic plant and its host plants. Specifically, we compared the species composition, density and host specificity of psylloids or jumping plant lice (Hemiptera: Psylloidea), inhabiting hemiparasitic box mistletoe Amyema miquelii, and three of its host Eucalyptus species: Eucalyptus blakelyi, Eucalyptus melliodora and Euca- lyptus polyanthemos. Insects were sampled by restricted canopy fogging in remnant Eucalyptus woodlands in an agricultural region of temperate south-eastern Australia. Although most psylloids are understood to be mono- or oligophagous, most species in our survey were found on the foliage of both mistletoes and eucalypts. Nevertheless, analysis of density patterns and reference to previous work on psylloids supports the high degree of host specificity for psylloids, leading to distinct assemblages on these two intimately associated plants. We show that (1) there were two mistletoe-associated species of psylloid and 18 eucalypt- associated species; (2) there were a large number of tourist species, as indicated by known psylloid/plant host associations; and (3) psylloid density was higher on eucalypt than mistletoe leaves. The different psylloid assemblages found on box mistletoes compared with their host plants are likely to be due to differences in the foliar properties implicated in host specificity and host selection by phytophagous insects. Further research is required to understand the ecological dynamics and evolutionary origins of these arbo- real assemblages. Key words arboreal, assemblage similarity, community composition, Psyllidae, tourist species. INTRODUCTION Studies of host specialisation of insects inform our understand- ing of species richness and turnover among host plants and locations and, thus, species diversity at different scales (Ødegaard et al. 2000; Dyer et al. 2007; Novotny et al. 2007). Variation in community composition among insect assem- blages is strongly influenced by host plant identity or plant species composition, particularly for phytophagous insects (Frenzel & Brandl 2001; Ødegaard et al. 2005). Mistletoes are parasitic plants that are physiologically linked with their host plants, and thereby strongly spatially associated, such that mistletoes and host plants share the same physical environ- ment and may appear to be one plant canopy (especially in cases of leaf mimicry by mistletoes, see Mathiasen et al. 2008). If plant chemistry and evolutionary history were not important, one would expect the assemblage of insects on mistletoe to be a nested subset of the assemblage on the host plant. However, mistletoes and their host plants usually belong to different orders and clades. The association between mis- tletoe and host plant offers an opportunity to explore factors that influence the host specificity, composition and distribution of arboreal arthropod assemblages in tree canopies. Although interactions between mistletoes and vertebrates have been well studied (as reviewed by Watson 2001; Watson & Herring 2012), much less is known about invertebrate assemblages associated with mistletoes. Species-specific studies have shown that ecological interactions between mis- tletoes and insects include herbivory, frugivory, pollination and tri-trophic relationships (Penfield et al. 1976; Atsatt 1981; De Baar 1985; Braby 2000, 2005; French 2004; Robertson et al. 2005). However, we are unaware of any direct compara- tive studies of arthropod assemblages on mistletoes and their host plants, apart from our own research (Burns 2009; Burns et al. 2011), and one indirect investigation of a food plant shift of a lepidopteran between a dwarf mistletoe and host conifers (Mooney 2003). *aeburns78@gmail.com Austral Entomology (2014) ••, ••–•• © 2014 Australian Entomological Society doi:10.1111/aen.12123