The conservation of native New Zealand butterflies in the ecologically enhanced farming landscape of Waipara, northern Canterbury

Abstract

Conventional farming landscapes suffer from low levels of biodiversity, and therefore a paucity of nature’s services – the products and services that ecosystems provide humans. This is largely due to the fragmentation and loss of habitats caused by intensive farmland management. However, attempts have been made recently to combine the theoretical principles of agricultural production and biodiversity conservation as they can be mutually beneficial. In the northern hemisphere, this relationship is formalised in the form of agri-environment schemes with varying degrees of success. Such compensatory schemes are not available in New Zealand so the incorporation of environmentally benign techniques that promote nature’s services is driven by research institutions and landowners themselves. The objective of this thesis was to quantify the effects of one such project on a group of non-target organisms in an intensively managed landscape in Canterbury. The native New Zealand butterfly fauna has not been studied in detail to date, but future conservation of these species may rely on less intensive farming methods. Enhanced butterfly populations may also act as an indicator of environmental health and subsequently assist in the marketing of wine. Measures were therefore also sought to enhance butterfly populations in such landscapes. Initial survey work showed that Waipara vineyards are poor habitats for butterflies. Planting plots involved in the “Greening Waipara” project did not support a large number of butterflies, probably because they were not designed with butterflies in mind and were too isolated from remnants. The habitat factors that were most important in explaining variation in butterfly populations were native shrub cover, legume cover (the host plant family of the most abundant butterfly species, Zizina oxleyi) and flower abundance. Enhancing these features in future conservation efforts is likely to enhance butterfly populations, although many other aspects of butterfly conservation are discussed. Subsequent experiments sought to indentify specific conservation issues in the Waipara region which the Greening Waipara project could help to address in future. In molecular and morphological analyses of the two Zizina species in New Zealand, the endemic Z. oxleyi and the introduced Z. labradus, contrasting results were found concerning their distributions. Such incongruence is not rare in the literature and may indicate recent speciation or hybridisation. These hypotheses are discussed in relation to the evolutionary history of the two species in New Zealand and the conservation of Z. oxleyi. Field and laboratory experiments supported the finding that nectar source provision may be suboptimal for butterflies in Waipara. In field survey work, perennial ‘weed’ species were the most visited flower species by adults of the common copper (Lycaena salustius). However, subsequent field and laboratory work showed that native Hebe spp. and Fagopyrum esculentum are more attractive and impart greater fitness benefits to adults than some of the ‘weed’ species currently available. In addition, host plant provision for L. salustius may not be optimal in Waipara. In laboratory performance experiments, larvae performed poorly on common host plant species. Conversely, females laid most eggs on F. esculentum, a novel host for this species on which larvae also developed poorly. Explanations for this choice by females may relate to the chemistry of F. esculentum relative to ancestral hosts. In the absence of F. esculentum, females preferred Muehlenbeckia astonii, a rare ancestral species which scored highly in larval performance assays. This thesis represents a relatively rare investigation into butterfly ecology in New Zealand and demonstrates the complexity in conserving butterfly populations. While research based recommendations are tentatively suggested for the enhancement of populations using inferences from northern hemisphere studies, further study is evidently required and the species encountered provide excellent opportunities for doing so.