Moths as potential pollinators in New Zealand.

Abstract

Despite being considered as important pollinators on a global scale, the role of moths as pollinators has been critically understudied, particularly the smaller more generalist moths (e.g. Noctuidae and Geometridae). This is particularly true for New Zealand, where a majority of studies on pollination have focused on birds, and studies on insect pollinators being targeted towards diurnal pollinators. The aim of this thesis was to examine the extent of research available to support moth pollination in New Zealand and how this compares to global understanding, determine moth-plant associations in a montane grassland environment and sub-Antarctic New Zealand, and to determine how effective moths are as pollen vectors in experimental conditions. Published New Zealand scientific literature and postgraduate student theses were searched for any mention of moth pollination, to determine how current knowledge of moths as pollinators in New Zealand relates to a global understanding (obtained from MacGregor et al. 2014). Systematic moth trapping took place across a range of elevations on Mt Cardrona (Central Otago, New Zealand) and in three different vegetation types on Enderby Island (Auckland Island archipelago, sub-Antarctic New Zealand). Pollen grains were removed from moth bodies to determine which moths interact with which plants, and how these interactions differ with elevation and across a range of habitat types. Experimental pollen transfer experiments were undertaken to determine the effectiveness of moths as pollen vectors. Results showed that New Zealand is heavily reliant on observations of visitation as evidence for moth pollination; while this is also true in the global literature, the presence of pollen on moth bodies is also used frequently to indicate moth pollination. Noctuidae and Geometridae are mentioned most frequently in New Zealand literature, reflected by the global literature. However, one moth family not mentioned in the global literature has been mentioned in New Zealand: Oecophoridae. Systematic sampling on Mt Cardrona revealed strong evidence for moth pollination of four plant genera; Dracophyllum, Acaena, Veronica, Wahlenbergia. While moths have previously been observed visiting Dracophyllum and Veronica species (e.g. Primack 1983; Thomson 1928), this work has indicated some previously unknown moth-plant associations. While Lloyd (1985) predicted moths may be important in sub-alpine communities, this work has been successful at showing moths may be more important than previously thought; a greater proportion of moths carried on average more pollen in the higher alpine sites, suggesting the role moths play as pollinators is more important in these higher alpine sites. Moths may also be capable of transporting pollen over longer distances than previously thought, however the data to support this is limited and further work is required. Systematic sampling on Enderby Island also revealed four plant species associated with moth visitation; Dracophyllum longifolium var. cockayneanum, Bulbinella rossii, Acaena minor and Gentiana concinna. A greater proportion of moths carried more pollen on average in the intermediate scrub vegetation, suggesting the role of moths as pollinators to be more important in this habitat type. Moths were active in wind speeds up to 6.6m/s and temperatures as low as 2.7°C, making the potential role of moths as pollinators in this region more important than previously thought. Moths may also be capable of transporting pollen over longer distances than previously thought, however the data to support this is limited and further work is required. Experimental pollen transfer experiments showed that moths are capable of transferring pollen between flowers in an artificial setting, the first documentation of this in New Zealand (to my knowledge). Combined with the presence of pollen on non-feeding Wiseana sp. discovered in Chapter 2, the pollen transfer rates between the feeding and non-feeding taxa used in these experiments suggests that flowers may be critical to moths for more than just food, however further investigation is required to discern these interactions. While this thesis has been successful in supporting the concept of moth pollination in New Zealand, future work is still required. In this study, sampling of the moth community occurred over a short period of time on Mt Cardrona and Enderby Island, as such, additional plants that moths potentially interact with not in flower at these times remain unknown. Future studies should trap moths at varying stages of the year and in varying habitats to determine additional moth-plant associations not identified in the course of this research. Future work should also aim to describe the effectiveness of moths as pollinators compared with other floral visitors; this can be done through the use of pollinator exclusion experiments, quantifying how effective moths are at transferring pollen between flowers, and how well this transfer of pollen results in the development of seed.