Seed Predation in weed communities: seed detection and discrimination and their impact on invertebrate seed foraging

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Competition from weeds remains a constant threat to agro-ecosystem productivity. Understanding why weeds occur where they do, or do not, is critical to improving weed management practices. To do this, we must develop a greater understanding of the ecological and evolutionary processes that govern weed population dynamics and thus, weed species distributions. Seeds are a vulnerable stage in plant recruitment and seed predation at the scale of weed patches may have the potential to limit the persistence and spread of weed patches. In some cases, seed predation has been observed to drive plant populations to extinction while in others, even massive mortality at the seed stage may have no impact on a given population. Seed foraging patterns and processes could be at least partially responsible for these discrepancies. Over the long-term, my research program will attempt to develop a comprehensive understanding of the role seed predation plays in shaping weed populations and communities. However, the mechanisms governing seed foraging and detection by invertebrates are currently not well-known; addressing this gap in our knowledge is a crucial step in further comprehending the importance of seed predation to weed communities. The specific objectives of this program are to: 1) determine and further explain the relationship between seed size and predator size in relation to seed choice, 2) assess physical seed traits and their influence on seed choice, and 3) determine the contribution of sensory modalities to seed detection and selection. I will use weed species known to differ in physical traits such as seed coat hardness and seed size to determine which of these traits drive seed choice. Chemical seed defense will be studied by identifying headspace volatiles, with the results used to design olfactometer-based studies that eludicate the impact of volatile compounds on seed choice. Ultimately, by helping to define the underlying mechanisms that determine seed selection, this research will aid our understanding of how seed predation impacts weed population dynamics and species distributions. This is important not just for maintaining crop yields and profits in agriculture, but also for reducing the impact of invasive weeds on the conservation and restoration of natural and semi-natural habitats.