Format: ORAL

Laura Lopresti1,2, A/Prof. Lori Lach2, Dr. Daniel Montesinos1,2

1 Australian Tropical Herbarium, James Cook University, Cairns, Australia 2 College of Science and Engineering, James Cook University, Cairns, Australia

The missed mutualist hypothesis proposes that when a species is introduced into a new range it may leave behind its mutualistic partners, which can lead to reduced fitness and prevent the species establishing and becoming invasive. Further, it has been hypothesised that specialist mutualisms are likely to impede invasion success due to the difficulty of attracting new specialist partners. The buzz-pollination syndrome encompasses specialised floral traits that restrict pollen access and requires a specialised bee behaviour for efficient pollen extraction. Yet, many invasive plants globally exhibit the buzz pollination syndrome. We used the buzz-pollination syndrome as a model to test the hypotheses that: (1) plant species exhibiting specialised pollination syndromes are underrepresented as invasive species, (2) species with specialised pollination syndromes that have become invasive can reproduce in the absence of specialist buzzing pollinators. Our review of global invasive species found evidence for buzz-pollination in 1.8% (82/4,630) of invasive angiosperms, which is an underrepresentation of the proportion of angiosperms that are estimated to exhibit this syndrome (6-10%). Most invasive buzz-pollinated plants are genetically self-compatible (97%), but only 43% can set fruit in the absence of a pollinator. We undertook assessments of the breeding system and pollinators of a highly invasive weed across the worlds tropics, Senna obtusifolia, in its native and invasive ranges. Senna obtusifolia is self-compatible and can set seed in the absence of pollinators. An analysis of the behaviour and pollen loads of floral visitors demonstrated that the specialist behaviour is not required to extract pollen from S. obtusifolia, depicting alternative foraging behaviours can be used to extract pollen from plants that exhibit the buzz-pollination syndrome. This is important where buzzing pollinators may be absent or not attracted to newly introduced plant species, potentially enabling invasions for plants that exhibit the specialised buzz-pollination syndrome.