Reproductive ecology and coexistence among trees in the Guineo-Congolian understory
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The exceptional tree biodiversity found in tropical rainforests is possible because many species coexist at low frequencies. While rarity may be an advantage when it comes to growth and survival, it may be a disadvantage in the context of reproductive success. Most tropical trees are adapted for pollination by animals, and populations at low densities and frequencies may be poorer competitors for pollination services and experience reduced reproductive success. Therefore, species that persist at low frequencies may have traits that help them cope with pollination when rare. Additionally, spatiotemporal variation in flowering patterns may alter the relative abundance relationships among species in ways that influence plant-pollinator interactions. We ask how biotic interactions, abiotic drivers and reproductive traits might interact to influence the reproductive success and persistence of cooccurring species. We answer this using spatially-explicit observational data from a guild of understory trees in Korup National Park, Cameroon, during the 2016 peak flowering season. In Chapter 1, we find that individual flowering probability is positively related to tree size and decreases with local species abundance, thus decreasing the relative abundance extremes among rare and common species during reproduction. It is not structured by shared ancestry and is unrelated to degree of neighborhood crowding or habitat differences. In Chapter 2, we find that the plant-pollinator interactions in this previously unstudied community are broadly ecologically generalized but that floral scent is a key trait involved in resource partitioning among insect groups, particularly among Diptera and Hymenoptera. In Chapter 3, we focus on the speciose Cola genus, and find that despite both morphologically generalized flowers and high pollination niche overlap, visitation rates are not sensitive to local or plot level flowering frequencies or floral display size and are uncorrelated with pollination success. Higher pollen limitation in abundant species compared to rarer species may be due to reproductive traits that promote outcross pollination. Together, these findings highlight the importance of understanding species reproductive dynamics from a community perspective and show that species trait differences may be key to understanding how pollination contributes to the persistence of rare species, and to biodiversity maintenance more broadly.
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Drager, Andrea Pilar. "Reproductive ecology and coexistence among trees in the Guineo-Congolian understory." (2020) Diss., Rice University. https://hdl.handle.net/1911/109594.