Optimising horticultural pollination services by evaluating the ecological mechanisms underlying species and community level processes

Abstract

<p>Improving the conservation and management of wild and managed insect pollinators is needed to increase the sustainability of global food security. In particular, refining crop-pollination management requires assessment of ecological processes occurring within pollinator communities and their interaction with plant traits. This thesis addresses three integral components of crop pollination: pollination in protected cropping environments, intra- and inter-specific processes central to plant-pollinator interactions in blueberry and the need for predictive models of pollinator body size to improve functional trait ~ pollination relationships.</p> <p>I conducted a systematic review and meta-analysis of the pollinator efficiency of managed insects for food crops grown in protecting cropping environments. I identified the pollinator fauna in three blueberry species (<i>Vaccinium</i> spp.) and undertook pollination limitation and single and multiple visit fruit set and weight experiments to ascertain each blueberry species’ pollinator dependence and pollinator species’ efficiency. I examined the influence of priority effects in species visitation order (either honeybees:<i>Apis mellifera</i> or native stingless bee: <i>Tetragonula carbonaria</i>) on fruit weight outcomes in blueberry (<i>V. corymbosum</i>) and raspberry (<i>Rubus idaeus</i>). I then assessed the colony dynamics of wild <i>T. carbonaria</i> populations foraging on blueberry flowers in relation to their floral visitation rates. Finally, using a global dataset of bee and hoverfly morphological measurements, I built predictive models to estimate body weight in these two important pollinator groups.</p> <p>Eusocial bees were the most commonly used managed pollinators in protected crops and both eusocial and solitary bees were similarly efficient in terms of fruit set, fruit weight and seed set. Significant issues facing pollination in protected cropping environments include environmental fluctuations and a general lack of knowledge in regards to pollinator health and longevity and stocking rates, and the efficiency and management of non-bee taxa. Australian grown blueberries are characterised by a pollinator community dominated by three bee species: <i>Apis mellifera</i>, <i>Tetragonula carbonaria</i> and <i>Bombus terrestris</i>. These pollinators were similar in their efficiency, yet their efficiency was dependent upon each blueberry species’ degree of pollen self-incompatibility. In mixed-species visitation sequences, species visit order priority effects were important in predicting fruit weight outcomes for blueberry but not raspberry. Blueberry flowers visited first by stingless bees resulted in larger fruit than those first visited by honeybees, however this effect diminished in longer floral visitation sequences. The number of wild <i>T. carbonaria</i> colonies found to forage in a given blueberry field ranged from 80 to more than 200 and floral visitation rates were correlated with intraspecific colony diversity. Models of pollinator body size as a function of the intertegular distance were highly predictive when taking into account species taxonomy, sexual dimorphism and biogeography.</p> <p>Management of both wild and managed pollinators is highly context-specific and requires consideration of ecological processes at the individual (i.e., functional traits), population (i.e., intraspecific diversity) and community (i.e., interspecific diversity and interactions) level. Greater consideration of plant reproductive requirements is required within crop-complexes such as blueberry, which differ in their reliance upon cross-pollination for fruit production and improved yields. A more holistic understanding of ecological processes central to pollination services across all levels of biological organisation will improve pollination management practices and help ensure global food security.</p>