Insect assemblages in a native (kanuka Kunzea ericoides) and an invasive (gorse Ulex europaeus) shrubland

In New Zealand, the European shrub gorse (Ulex europaeus) is becoming the initial post-disturbance shrub, replacing the native myrtaceous manuka (Leptospermum scoparium) and kanuka (Kunzea ericoides) scrub in this role. Change in the dominant vegetation is likely to affect the native invertebrate community. To quantify these changes, we compared the assemblages of four selected insect taxa (Coleoptera, Lepidoptera, and two groups of Diptera, the Tachinidae and the fungus gnats, represented in New Zealand by the families Ditomyiidae, Keroplatidae and Mycetophilidae) in neighboring stands of kanuka and gorse using Malaise and pitfall traps set during December. We sorted 34 387 specimens into 564 recognisable taxonomic units. Ordinations showed that insect assemblages associated with each habitat were distinct for all four insect groups. The gorse habitat was species rich compared with kanuka for tachinids, fungus gnats and Malaise-trapped beetles, and both habitats contained few adventive species. Many species were unique to each habitat. Some species loss might occur if the kanuka-dominated community continues to be replaced by gorse, but gorse is nevertheless considered to be valuable as a habitat for native invertebrates.