Iris douglasiana

Abstract: Chloroplast DNA (cpDNA) markers were developed that provided markers unique to a species or that delimited a large area within a species. These markers were then followed across two hybrid zones: Iris douglasiana/lIris innominata, and Iris chrysophylla/lIris tenax. In each case the cline in haplotype frequency was compared to the cline for a morphologically based hybrid index. In all three transects across the I. douglasianall. innominata hybrid zone, the cpDNA cline was displaced 1-2 km relative to the morphologically defined hybrid zone; the displacement was not found in the other hybrid zone. The observed displacement represents introgression of cpDNA from I. douglasiana into I. innominata. It may be that the I. douglasianall. innominata hybrid zone has shifted in recent time, leaving the slowly dispersing chloroplast DNA behind. The populations known as Iris thompsonii do not form a phylogenetic species and are best viewed as products of hybridization between I. douglasiana and I. innominata.

Abstract: The reproductive biology of a population of Iris douglasiana was studied at the University of California's Marine Biological Station at Bodega Bay. The main pollinators of this copious nectar-producer are long-tongued, nectar-collecting bees of three genera, Emphoropsis, Bombus and Anthophora. Although I. douglasiana is a vigorous vegetative reproducer, outcrossing in this species is increased through the interaction of nectar flow, flower phenology and pollinator behavior. The flowers are protandrous, with a peak nectar production on the 1 st day of stigma receptivity. Pooling of the nectar allows bees to remove most of the liquid reward from any one of the three floral units of each I. douglasiana flower. Bees have a strong tendency to visit only one unit of each flower before flying to another flower, thus increasing the possibility of outcrossing. Bees also show a consistently strong directionality in their flights, while showing no difference in the distance flown on calm or windy days. Pollinators do not appear to use the presence of nectar as a cue for visitation, but there is a correlation between stigma receptivity and avoidance of that flower by bees.

Abstract: Acroceridae is a family of spider-parasitic flies that often visit flowers as adults, although little is known about their possible role as pollinators. Eulonchus tristis Loew visiting flowers of Brodiaea elegans Hoover (Liliaceae s.l.) and Iris douglasiana Herbert (Iridaceae) were collected in California. Individuals carried large pollen loads, although visitors to B. elegans carried significantly more pollen grains than visitors to I. douglasiana. Visitors to B. elegans also carried a higher percentage of focal-plant pollen (91%) than visitors to I. douglasiana (38%). There was no difference in the diversity of pollen species (approximately nine) carried by visitors to either plant species. For visitors to B. elegans, no difference was seen in the amount or diversity of pollen carried with respect to the sex of the visitor. The behaviour potentially resulting in the acquisition of these pollen loads is discussed. These results show that E. tristis has the potential to be an important pollinator for thes...