Pollen flow influences key ecological processes including reproductive success, gene flow, and spatial genetic structure. Pollen movement and the diversity of pollen sources has been well characterized for many plant species for discrete time periods, such as a single breeding season. Yet, relatively little is known about the degree to which pollination dynamics vary within a plant population over longer time periods and what factors may drive this temporal variation. Moving from 'snap-shot' studies to understand temporal variation in pollination dynamics therefore represents an important advancement for plant ecologists. Among plant species that are pollinated by animal vectors, differences in the spatial distribution of concurrently flowering adults is likely to impact pollinator movements, which in turn may impact pollen movement and diversity. Here, we investigate the impacts of density (defined as abundance of concurrently flowering conspecifics in a population) and clustering (defined as abundance of concurrently flowering conspecifics within the local pollen neighborhood) on pollen movement and pollen pool diversity in the tropical palm Oenocarpus bataua over a five-year period. To do so, we used a combination of microsatellite analysis from offspring collected from geolocated maternal trees and a phenology record to calculate density and clustering for each maternal tree.
Results/Conclusions
Using nine microsatellite loci, we genotyped 854 offspring from 41 progeny arrays that were collected from 37 distinct maternal trees from 2012-2017. We observed substantial variation in pollen movement over time, and found that clustering has a strong effect on both pollen movement and pollen pool diversity. The mean, minimum, and maximum distance pollen traveled had an inverse relationship with clustering, indicating that the more dispersed pollen resources were, the further pollen was moved. In contrast, the number of effective fathers (Nep) showed a significantly positive relationship with clustering. Furthermore, no significant relationships were found between pollen diversity or movement and density. These results indicate that patterns of pollen flow may change considerably over time within a single system as a function of the distribution of concurrently flowering adults, highlighting the need for longitudinal studies, particularly in tropical systems. More broadly, this study indicates the causal role of clustering of flowering adults in driving animal-mediate pollen flow.