GEIGER, JOHN H. Florida International University, University Park, Dept. of Biological Sciences, Miami, FL., 33199. - Pollination and reproduction of Ruellia succulenta Small in pine rockland fragments.
The purpose of this research was to study the effects of habitat
fragmentation on pollination and reproduction of Ruellia succulenta
Small (Acanthaceae). Many studies have documented reduced seed set in
plants occurring in fragments relative to plants in continuous
habitat. The mechanisms explaining this reduction in reproduction have
generally been resource limitation, pollinator limitation, and genetic
erosion/inbreeding depression. My study focused on resource and
pollinator limitation. I chose three sites in each of the following
four size classes of habitat: small (< 3 ha), medium (3-9 ha), large
(> 10 ha), and intact (in Everglades National Park). At each site, 20
randomly chosen plants were tagged. All plants were surveyed weekly
for a year and data were collected on # of open flowers, # of mature
fruit, # of seeds/fruit, and seed predators/fruit. If present, stigmas
from untagged plants were mounted in Fuchsin gel on microscope slides.
These were analyzed for number of conspecific and heterospecific
pollen grains. If open flowers were present, timed pollinator watches
were performed. Number and identification of floral insect visitors
were recorded. The results of the ANOVA test on area of site and the
three reproductive variables all were highly significant but the trend
of reduced reproduction in smaller size classes was not shown. All
three reproductive variables had highly significant negative Spearman
rank correlations with the factor time since last fire. There appeared
to be no correlation between conspecific/heterospecific pollen on
stigmas (indirect measure of pollination) and either area of site or
time since last fire. There were highly significant differences in the
proportion of the orders of flower visiting insects by site. In
conclusion, reduced seed set appeared to be the result of resource
limitation (light and nutrients) rather than pollinator limitation.
Fragmentation did, however, affect the composition and abundance of
the pollinator guild.
Key words: fragmentation, pollination, pollinator guilds, Ruellia succulenta, seed set