3D pollination biology of cacao
Project
ID: 000461839
Public
Despite the economic importance of chocolate and that insect pollinators have been shown to limit cacao crop yields, little is known about the highly specialized pollination biology of Theobroma cacao L., and even less about its relatives, Byttneria spp., Ayenia spp., and Guazuma spp. For pollination, insects must go through Cacao’s bizarre petals (petal sacs) to come into contact with the pollen-containing anthers. Then, they need to either escape the petals and fly to another flower (for cross pollination) or come into contact with the pollen-receiving stigma (for self pollination). Acquiring and depositing pollen via movement through these intricate 3-dimensional structures is size- and geometry-specific. For example, if an insect is too small or not the right shape, it could crawl through the flower without interacting with the anthers or stigma at all. Ceratopogonid midges (Diptera) are often named cacao’s main pollinator, but field studies have found higher visitation rates for other small dipterans. It is also possible that different insects are responsible for population across cacao’s range. To determine the functional size limits of cacao’s pollinators, 3D measurements of floral structures can be used and compared with suspected pollinator dimensions to make hypotheses on which floral visitors are most likely to be successful. To precisely quantify plant-pollinator geometry and functional size limits of an effective pollinator for cacao and its relatives, we are using microcomputed tomography (micro-CT) and 3D geometric morphometrics.