Weather, Pollination and the Phenology of Geranium maculatum

Abstract

-We examined spatial and temporal patterns of pollen receipt, pollen removal and maternal reproductive success in Geranium maculatum. These three variables differed among sites and sampling dates. Sites with the densest tree canopy had the lowest pollen receipt and fruit production. Differences between years were accompanied by different climatic conditions and may have been caused by different levels of pollinator activity. Within blooming seasons, fruit production and pollen receipt declined at all sites with date, accompanying canopy closure. Pollen removal varied with date, but not in parallel with pollen receipt, indicating that pollen receipt and deposition were influenced, in part, by different factors. Of three weather variables examined, ambient temperature was significantly positively correlated with rate of floral development, but not consistently with pollen receipt, pollen removal or fruit production. Pollen receipt was inversely related to cloud cover, presumably due to effects of the latter on pollinator activity. The earliest-blooming plants had the highest reproductive success.