The degree of reproductive synchrony in plant populations defines several important ecological dynamics. At the population level, reproductive synchrony defines patterns of cross-pollination, and therefore shapes genetic diversity and structure. At the individual level, synchrony influences the intensity of fitness-related, density-dependent processes like herbivory, seed predation, pollination and seed dispersal. In spite of its profound consequences, the factors that drive different degrees of reproductive synchrony among individuals in a population remain poorly understood. We analyzed the reproductive phenology of a premontane Ecuadorian palm, Oenocarpus bataua, to explore the role of genetic relatedness and geographic distance among individuals as drivers of the degree of reproductive synchrony among trees within a single population.
In an Ecuadorian site (7900450W, 000220N; elevation: 436–615m), we geolocated, genotyped all adult trees and documented the reproductive stage of each one over a period of 9 years. We computed the degree of reproductive overlap (synchrony) for each pair of individuals through the study period, and evaluated the effects of genetic relatedness (Loiselle’s Kinship Coefficient) and geographic distance using simple matrix regression and Mantel correlograms respectively.
Results/Conclusions
We observed significantly lower synchrony for trees flowering and bearing mature fruits at small distances from each other (<95m for flowering, <190m for mature fruits). In contrast, we observed no significant associations between genetic relatedness and reproductive synchrony.
We show that synchrony patterns within populations can have an underlying spatial structure, and suggest small-scale geographic distance might modulate them through its effect on density-dependent processes such as herbivory and dispersal services. Our results also suggest that spatially dependent processes could predominate over genetic factors to determine patterns of reproductive synchrony in tropical plant populations. Although our results are suggestive, further work on the genetic underpinnings of reproductive development in O. bataua and direct assessment of the effects of density on fitness-related processes such as herbivory and dispersal services are needed to determine the mechanisms underlying our results.