Pollen transport by insects in the Australian Alpine

Abstract

Pollinating insects contribute to the reproductive success of the vast majority of flowering plants. Pollination services are under threat as from global climate change and habitat degradation which change pollinator and plant communities and disrupt the interactions between them. Little is known about how the functional traits of flower visiting insects influence their ability to pollinate plants. Understanding how functional traits affect pollen transport by insect pollinators will improve predictions of how anthropogenic-driven changes to pollinators will impact floral communities. Additionally, most plant-pollinator research does not consider the importance of pollen transport by individual insects, rather organising them into taxonomic groups and therefore overlooking differences between individual and species-level visitation. This thesis analysed the pollen transport of flower visiting Hymenoptera, Diptera, Coleoptera, and Lepidoptera in the Australian Alpine by quantifying pollen loads removed from the respective body parts of individuals, separately. The functional traits body size, mouthpart length, hair length, and hair density of a range of insects were measured. Single visit pollen deposition (SVD) experiments were conducted on various plant-insect interactions. The mouthpart traits of Incurviseta (Lauxaniidae), a super-abundant pollen-feeding fly were imaged using a scanning electron microscope. Several species of bees and Diptera transported large pollen loads with high proportions of conspecific pollen. Diptera and Hymenoptera carried highly conspecific pollen loads because the individuals that summate their species are florally constant. Individual-level networks had lower nestedness and connectance but higher specialisation than species-level networks, underlining the need to recognise individuals separately from their parent species. The body parts of individuals had different compositions of pollen, mostly due to differences in floral morphologies, insect body sizes, and insect foraging behaviour. Grooming in bees resulted in most pollen being concentrated on their legs and dorsal thorax. Body size moderately influenced pollen load size, and the hair length and mouthpart length of Diptera moderately influenced their pollen load sizes and richness. Hair density did not influence pollen transport. SVD experiments revealed that Diptera are likely pollinators of Baeckea utilis. Diptera in the genus Incurviseta were found to have mouthpart traits enabling it to feed on a large quantity and of pollen from a diverse range of plants. This thesis addresses the importance of functional traits, both morphological and otherwise, for pollen transport, and identifies large-bodied Diptera and bees as being potentially important targets for future research and conservation in the Australian Alpine. Show more