RATHCKE, BEVERLY J. Department of Biology, University of Michigan, Ann Arbor, MI 48109. - After the hurricane: pollen- and resource-limitation of fruit set in the bird-pollinated, endemic Bahama swamp-bush, Pavonia bahamensis Hitchc. (Malvaceae).
Bahama swamp-bush, a shrub endemic to the Bahama Islands, appears to
be exclusively pollinated by two bird species on San Salvador Island:
bananaquits and Bahama woodstars. The populations of these
nectarivorous birds apparently were decimated by Hurricane Lili in
October 1996 which stripped most plants of their floral resources and
leaves. After this hurricane, these birds were seldom seen visiting
flowers of Bahama swamp-bush during the major winter flowering period
in 1996-7, and 49% of the flowers had no pollen deposition on stigmas.
In contrast, in winter 1994-5, these birds were frequent flower
visitors, and only 2% of the flowers had no pollen deposition.
Correspondingly, fruit set (fruit/flower) declined dramatically from
82% in 1994-5 to 11% in 1996-7. Based on pollen augmentation
experiments, this reduced fruit set was caused by both
pollen-limitation and resource-limitation. In several other studies,
severe hurricanes have been demonstrated to devastate populations of
nectarivorous birds. These results indicate that hurricanes can
substantially limit the fruit set of bird-pollinated plants, both
indirectly through effects on bird pollinators and directly through
resource limitation.
Key words: bird pollination, hurricane effects, Pavonia bahamensis (Malvaceae), pollen limitation of fruit set, pollination, resource limitation of fruit set