Selective enhancement of native flora for diverse and sustainable pollinator populations in Australian agroecosystems under climate change

Abstract

Plant-pollinator interactions represent one of the most important mutualisms in nature. Globally, about 88% of angiosperm species rely on pollination by animal visitors in order to fruit and set seed. At the same time, pollinators are rewarded with food in the form of nectar and pollen. Pollination is a critical ecosystem service underpinning plant reproductive success and associated yields for crop species; however, around the world, many populations of wild insect pollinators are in decline, while the dependence on a single agricultural pollinator – the European honeybee (Apis mellifera L.) – is increasing. In Australia, many agroecosystems rely on pollination services from insects, while being in the fortunate position that feral and managed honeybee populations have not yet been decimated by the Varroa mite (Varroa destructor). As Varroa mite establishment seems inevitable, wild pollinators will have an even more vital role to play in the future, from both an ecological and a food security perspective.

My research illustrates that temperature effects differ greatly between plant species. Under warming, several species exhibited shifts in flowering phenology and a reduction in the number of flowers produced. I further found changes in the level of plant investment towards lower total aboveground biomass and a reduction in relative biomass allocation to reproductive, compared to vegetative, growth. Overall, results suggest that moderate warming can stimulate nectar production along with increases in the number of nectar- producing flowers and nectar sugar concentration. Shifts in the timing and amount of floral resources produced can ultimately reduce resource provisioning to pollinators and thus the resilience of pollinator communities. As responses to warming were shown to be species- specific, diversifying native plant habitat with a wide range of plant species may provide some insurance against the effects of climate change at the community level.

Ultimately, my PhD thesis contributes to a better understanding of factors that drive insect visitation within a flowering community and assist to promote and conserve different insect pollinator groups for the safeguarding of pollination service delivery within highly altered agroecosystems. My research identifies the importance of floral trait diversity and overlapping flowering phenologies for supporting diverse native pollinator populations, both today and in a future, warmer world. I further highlight how high-quality, locally sourced seed mixes comprised of predominantly perennial native plant species with a variety of floral traits can improve floral resource supply to native pollinators as part of floral enhancements in a wide range of systems.

Date of Thesis submission	2021
Original language	English
Awarding Institution	Western Sydney University
Supervisor	Sally Power (Supervisor), Amy-Marie Gilpin (Supervisor), James Cook (Supervisor), Paul Rymer (Supervisor) & Paul Gibson-Roy (Supervisor)