Macroinvertebrate Community Responses to Mammal Control
MACROINVERTEBRATE COMMUNITY RESPONSES TO MAMMAL CONTROL – EVIDENCE FOR TOP-DOWN TROPHIC EFFECTS BY OLIVIA EDITH VERGARA PARRA A thesis submitted to the Victoria University of Wellington in fulfilment of the requirements for the degree of Doctor of Philosophy in Conservation Biology Victoria University of Wellington 2018 Para mi sobrina Violeta Orellana Vergara y su sonrisa hermosa. Tu llegada remeció mi corazón de amor de una manera inimaginable. ¡Sueña en grande! ii Nothing in nature stands alone... (John Hunter 1786) iii iv ABSTRACT New Zealand’s invertebrates are characterised by extraordinary levels of endemism and a tendency toward gigantism, flightlessness and longevity. These characteristics have resulted in a high vulnerability to introduced mammals (i.e. possums, rats, mice, and stoats) which are not only a serious threat to these invertebrates, but have also altered food web interactions over the past two-hundred years. The establishment of fenced reserves and the aerial application of 1080 toxin are two methods of mammal control used in New Zealand to exclude and reduce introduced mammals, respectively. Responses of ground-dwelling invertebrates to mammal control, including a consideration of trophic cascades and their interactions, remain unclear. However, in this thesis, I aimed to investigate how changes in mammal communities inside and outside a fenced reserve (ZEALANDIA, Wellington) and before-and-after the application of 1080 in Aorangi Forest, influence the taxonomic and trophic abundance, body size and other traits of ground-dwelling invertebrates on the mainland of New Zealand. I also tested for effects of habitat variables (i.e. vegetation and elevation), fluctuations in predator populations (i.e.
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