The reproductive biology of Weigela subsessilis and W. florida and barriers to hybridization between two species were examined. In the floral color-changing species, W. subsessilis quercetin glycosides predominated in flora tissue at first deceasing in number and quantity with time by enzyme FLS and two cyanidin 3-0-glycosides became present predominantly in flower color changing tissue from yellow to mauve by enzyme ANS3GT. The cause of the color changing pattern is not certain yet. Weigela florida and W. subsessilis occasionally occur sympatrically, sometimes bloom synchronously, have similar flora morphology and require pollination by insects to set seed. Crossing experiments and pollinator observation at sites where they occurred sympatrically suggested that W. subsessilis and W. Florida were almost self-incompatible, with a mostly mixed mating system possibly facilitated by andrenid bees (Andrena halictoides). Flowers that were self-pollinated, cross-pollinated and hybridized showed ca, 10%, 100% and 100% fruit-set, respectively. Geitonogamic pollination resulted in fruits with significantly less seeds that open- and cross-pollinations between species and within the species. Andrenid bee and others were characterized by non-discriminating behavior for collecting pollen and were commonly found in both W. subsessilis and W. Florida. Barriers to hybridization between two species consisted of divergence mainly in a series of prezygotic isolating mechanisms such as ecological (habitat difference) and seasonal isolating mechanisms. The major morphological features and flavonoids chemistry of W. hortensis in Korea shared with those of either W. Florida and W. subsessilis suggested that these might have been derived from a hybridization event. The common observation of this current study, however, was the strong floral constancy exhibited by visitors to the Weigela species, which suggested that interspecific pollination had low potential to cause divergence in morphology. The following study will focus on whether or not tension zone of the putative hybrid, W. hortensis is present and clarify the existence of hybrid unfitness and parental dispersal.
PDF Links
Full text via DOI
Download Citation 
