Associations Between Weevils (Coleoptera: Curculionidea) and Plants, and Conservation Values in Two Tussock Grasslands, Otago, New Zealand

Ecosystem level processes and species interactions have become important concepts in conservation and land management. Despite being New Zealand’s greatest contributors to global diversity, native invertebrates have been largely overlooked in the assessment of land values, and their diversity has often been assumed to reflect native plant diversity without justification. Invertebrates can in fact affect plant species composition, and in ecosystems such as New Zealand’s remaining indigenous and semi-modified tussock grasslands can do so in excess of more conspicuous vertebrate grazers. An understanding of the interactions between invertebrates and their plant hosts may be informative in assessing land conservation values, increase the efficiency of rapid inventory analyses and would be applicable across the production-conservation spectrum. This study considers the Curculionoidea, vascular plant, bryophyte and lichen communities of two semi-modified tussock grasslands in the Otago region of southern New Zealand. Quantitative plant and invertebrate sampling were carried out in January 2001. Data were analysed using ANalysis Of SIMilarity (ANOSIM) and Multi-Dimensional Scaling (MDS) ordination techniques. Vascular plant, bryophyte and lichen species richness was highest in the same site and plots as native weevil species richness, however the proportion of native vegetation in these locations was lower. Associations identified between Curculionoidea and vascular plants were dismissed due to the confounding effect of species frequency across samples. This appeared to have little influence on associations with bryophytes and/or lichens and these were given more weighting. The ecological implications of associations are considered and variability in weevil composition is discussed in reference to the tussock grassland environment. The importance of plant–invertebrate relationships to conservation and the uses and limitations of the PRIMER MDS ordination technique for determining associations are discussed.