PARENT SESSION
Oral Session #81: Pollination and Dispersal.
Presiding: T. Ricketts
Thursday, August 8. 9:00 AM to 11:30 AM. Grand Ballroom Central, Radisson.
Mosaic landscapes, isolation, and pollination.
ELMQVIST, THOMAS*,1, LUNDBERG, JAKOB1, AXELSSON, SANDRA1, CHAN, WAN-YING2, BANACK, SANDRA2, 1 Stockholm University, Stockholm, Sweden2 California State University, Fullerton
ABSTRACT- We are currently witnessing a dramatic change in land use with an increasingly skewed size distribution of habitat remnants, with a few large and many small patches. Habitat fragmentation immediately reduces the size of populations, increases their isolation, surrounds them in a matrix consisting of new environments and commonly changes their biotic environment. Specialist pollinators may rapidly disappear in small fragments either as an effect of small fragment size and diminished sources per se, or as an effect of increased competition from generalist pollinators. Plant species may show different vulnerabilities to declines in pollinators. Isolated populations of obligately outcrossing plant species with specialized tubular flowers and small rewards may suffer a much higher risk of extinction when pollinators decline compared to a similarly isolated population of at least partly self-pollinating plant species with open generalized flowers. In field surveys and studies of experimental populations of the dioecious Silene dioica in an archipelago of islands differing in size, vegetation cover and distances to the mainland, we addressed the following questions: a) does the size of an island and distance to mainland affect the size and composition of the pollinator guild, b)does variation in pollinator guild composition influence the seed set of Silene dioica, and c) is there a temporal variation in the risk of pollen limited seed set? The results of the surveys and experiments suggest that island size and distance influence the composition of pollinator guilds with generalist pollinators being relatively more dominant on small and isolated islands. Seed set of the experimental populations of Silene dioica was not affected by island size and isolation in the early part of the flowering season, while later in the season, seed set was significantly reduced on islands near the mainland.
KEY WORDS: pollination, isolation, generalist