Invertebrate Diversity Associated with Tropical Mistletoe in a Suburban Landscape from Northern Australia

Abstract

The invertebrate fauna associated with the tropical mistletoe Decaisnina signata (Loranthaceae) parasitising a range of host trees was surveyed during the late dryseason (September-October) in suburban areas of Darwin, Northern Territory, a landscape which comprises extensive patches of natural vegetation within the urban matrix. A total of 113 species of insects and spiders representing 51 families and 12 orders was recovered from 38 samples. The estimated total species richness, however, suggests another 116 species are likely to occur on the mistletoe according to the incidence-based coverage estimator (ICE). Hymenoptera (especially Formicidae), Hemiptera (particularly Miridae), Araneae and Lepidoptera were the most dominant groups in our samples in terms of both species richness and relative abundance (measured as % site occupancy). Thysanoptera, Coleoptera and Psocoptera were also comparatively diverse but were substantially less abundant. Overall species and family richness were both positively correlated with mistletoe biomass, but the composition and taxonomic richness of invertebrates associated with mistletoes parasitising different host genera (Planchonia vs. Alstonia) or host species (Alstonia scholaris vs. A. actinophylla) were not significantly different. Our findings are in broad agreement with limited previous studies elsewhere that indicate mistletoes support a wide range of invertebrates, some of which are obligate specialists. We hypothesize that mistletoes support a unique assemblage of invertebrates that is independent of the host tree.