How does ecological restoration influence invertebrate composition on Quail Island?

Abstract

Ecological restoration in New Zealand has an emphasis on the islands due to its feasibility of mammal control. As a refuge of local, rare and endangered species, ecological restoration has been undertaken on Quail Island for 19 years from 1998. To evaluate the response in biodiversity, the invertebrate community was used as a bio-indicator to assess the restoration success. In this study, we examined the change in the terrestrial invertebrate community by pitfall traps across five different habitats including exotic grassland, restoration plantings of two ages, mixed shrubland, and pine and macrocarpa woodland. Species diversity was tested by Shannon index, Simpson’s index, beetle richness and mite richness. We used the general linear model to examine the change in time and identify the influence of environmental variables. Species-level association with habitat structure was tested by pairwise comparison. We saw an apparent increase in Shannon index, Simpson’s index and beetle richness, while mite richness fluctuated. Habitat differences illustrated the species preference for habitat structure. Restoration trajectories indicated a promising recovery of the invertebrate community, especially for cave weta (Pleioplectron simplex) and ground weta (Hemiandrus n. sp.). The catch of Megadromus guerinii, the first Bank Peninsula endemic found on Quail Island, showed its potential to be the suitable habitat for local species. The analysis of the species abundance with the environmental factors indicated their requirement of physical characteristics. The comprehensive results of 19 years restoration revealed the current state of biodiversity that contribute to the future restoration plan. Although the nature of long-term monitoring and methodologies used raised several uncertainties and concerns of the results, continuous monitoring is recommended to ensure the succession of the ecological community is under control to reach the final goal.