Abstract Detail

Reproductive Processes

Drager, Andrea Pilar [1], Chuyong, George [2], Kenfack, David [3], Thomas, Duncan [4], Dunham, Amy [5].

Pollination ecology of seven co-flowering Cola spp. at different densities in an Afrotropical forest: geitonogamy not floral neighborhood drives pollination outcomes.

Tropical forests are notable for their species-rich tree genera, yet how so many similar species co-occur, despite the potential for reproductive interference, is still little understood. The density and composition of the flowering neighborhood can influence pollinator-mediated interactions. Due to their lower numbers, rarer congeners may face greater challenges when competing for pollination services, leading to poorer pollination outcomes. We studied the pollination ecology of a group of seven co-flowering monoecious Cola spp. found at differing abundances in the Afrotropical understory. We modeled both floral visits and pollination success of an individual tree at a particular sampling date as functions of the density of: flowering conspecifics, congeners weighted by pollinator niche similarity, and all heterospecifics, at both local (10m, 20m) and 25ha plot scales. Our models accounted for a tree’s floral surface area, and sexual morphology at sampling time. All species had actinomorphic flowers visited by diverse insects, though flies, ants and beetles dominated. Floral surface area of the focal tree was negatively related to visitation, but not pollination. Neither visitation nor pollination was sensitive to any measure of flowering density at local scales, but at the plot scale, pollination outcomes showed a negative relationship with conspecific density: pollination outcomes were highest for low- and intermediate-density species, as well as for individuals of abundant species flowering outside of their peak. The presence of male flowers was important for pollination success across species, suggesting pollen transfer within trees, rather than pollinator movement among trees, contributed to high pollen tube counts. Rarer species were as, or more, successful than their abundant congeners, suggesting species differences interact with flowering density to mediate pollination outcomes. However, the low levels of pollination in trees lacking male flowers suggest there is pollen limitation to seed set across species in this genus of tropical trees.

1 - Rice University, Biosciences, 6100 Main Street, MS-170,, Houston, TX, 77005, USA
2 - University of Buea, Department of Botany and Plant Physiology, PO Box 63, Buea, SW, Cameroon
3 - Smithsonian Tropical Research Institute, Center for Tropical Forest Science-ForestGEO, PO Box 37012, Washington, DC, 20013, USA
4 - University of Washington, Vancouver, Biology, 14204 NE Salmon Creek Ave, Vancouver, WA, 98686, USA
5 - Rice University, Biosciences, 6100 Main St., MS-170, Houston, TX, 77005, USA

Keywords:
Pollination
relative abundance
density
co-flowering
tropical trees.

Presentation Type: Oral Paper
Session: REP1, Reproductive Processes 1
Location: San Luis 2/Starr Pass
Date: Wednesday, July 31st, 2019
Time: 10:30 AM
Number: REP1010
Abstract ID:378
Candidate for Awards:None