Flowering asynchrony in a population changes densities of flowering plants throughout a season. Few studies have examined how pollen mediated gene dispersal changes over the course of a flowering season. We investigated this relationship in a generalist-pollinated prairie perennial, Echinacea angustifolia. In addition, we examined the importance of seed ripening phenology, which is tightly linked to flowering phenology, in seed harvesting for ex situ conservation. There are many components of flowering phenology, including start and end dates, synchrony, skewness, intensity, and duration. We analyzed how each component influences pollen movement in a naturalized experimental plot. To characterize pollination patterns paternity was assigned to offspring using ten microsatellite loci. Candidate fathers included all 204 flowering plants in the experimental plot and twenty plants from a nearby population 250 meters away. For each of 30 maternal plants, 30 offspring were genotyped– ten offspring each from the beginning, end, and middle of the maternal plant’s flowering duration. Three methods of paternity analysis were compared, exclusion, maximum likelihood, and fractional allocation.
Results/Conclusions
Over 3% of pollinations came from plants at least 250 meters away, and nearly all of these gene flow events occurred either early or late in the flowering season when flowering plant densities were at their lowest. For individual plants, pollination distances were significantly greater at the beginning and middle of the plant’s flowering season than at the end. These findings demonstrate that flowering phenology can play an important role in pollen mediated gene dispersal in a generalist-pollinated herbaceous plant. Our findings have implications for habitat fragmentation since flowering phenology alters gene flow between nearby fragmented populations.
Seed harvesting is central to many aspects of ex situ conservation. Most seed harvesting protocols are based upon the number of maternal plants sampled with an assumption that there are more or less an equal number of paternal plants represented among the seeds of each maternal plant. However, we found significantly more paternal plants represented in seeds from early and peak harvested plants than from late harvested plants. Thus, phenology should be considered for seed harvesting when the goal is to maximize the genetic diversity sampled from a population for either restoration purposes or seed banking.
