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.
The effects of habitat fragmentation on pollinator visitation rates and fruit and seed production on a tropical tree, Tabebuia rosea (Bertol.) DC (Bignoniaceae).
JOHNS, JENNIFER*,1, HANDEL, STEVEN2, 1 Willamette University, Salem, OR2 Rutgers University, New Brunswick, NJ
ABSTRACT- In examing the effects of habitat fragmentation on a given species, the researcher, policy maker, and land manager ultimately want to answer the question: is lifetime fitness compromised by habitat fragmentation? Is the species at risk of local extinction? A number of attributes of habitat fragments may act alone or in concert to contribute to a reduction in fitness, including increased exposure to edge effects, increased isolation, decreased diversity and population size and/or density, and a change in the geometry of the population and the landscape matrix. The consequences of these various effects of fragmentation may be similar. For instance, both increased isolation and decreased population size could lead to a reduction in mate availability. We investigated the effects of habitat fragmentation on the reproductive success of a self-incompatible tropical tree, Tabebuia rosea, in the Barro Colorado Nature Monument in the Republic of Panama. We studied trees in three habitat types: small forest fragments (3-10 ha), edge habitat of a large continuous forest, and interior forest. We found that the number of pollinating visits varied among forest fragments, edge habitats, and interior forests, for different bee species, but there was no significant difference in total number of visits. However, significantly less pollen was delivered to flowers on trees in forest fragments than to flowers on trees in the edge or interior habitats. This difference persisted in the number of seeds produced per fruit. That is, trees in forest fragments produced significantly fewer seeds per fruit than trees in edge habitat and trees in interior forest. Fruit production, standardized by cm dbh, varied considerably within each habitat type. Consequently, there was no significant difference in fruit production among the three habitats. A significant reduction in seed production could affect the lifetime fitness of individuals in forest fragments, particularly if the seedlings produced are less robust or have a higher rate of mortality in the field. Subsequent studies of this species indicate that early seedling growth is significantly reduced in seedlings produced by trees in forest fragments.
KEY WORDS: pollination, forest fragmentation, Barro Colorado Nature Monument, fruit and seed production