PARENT SESSION
Oral Session #45: Biogeography and Metapopulations.
Presiding: T. Miller
Tuesday, August 6. 1:00 PM to 4:45 PM. Grand Ballroom Central, Radisson.
Metapopulation dynamics at two scales in Polygonella basiramia (Polygonaceae), a Florida scrub endemic plant.
Boyle, Owen*,1,2, Menges, Eric2, Waller, Donald1, 1 University of Wisconsin, Madison, WI2 Archbold Biological Station, Lake Placid, FL
ABSTRACT- Metapopulation ecology is concerned with the effects of local population dynamics, namely extinction and colonization, on the regional persistence of a species. The metapopulation approach is a useful tool for managing populations of many endangered species, but has seldom been applied to plants. We studied the metapopulation ecology of Polygonella basiramia, a short-lived perennial herb endemic to Florida scrub, occurring primarily in networks of open sand gaps within a shrub matrix. We observed metapopulation dynamics at two spatial and temporal scales: between 88 shrub patches (over 10 years at a ca.100 m, i.e. "large-scale"), and between 1,228 gaps within 19 shrub patches (over 3 years at a ca. 1 m, i.e. "small-scale"). While patch isolation played a greater role in predicting occupancy at the large scale, patch area explained a greater portion of the variation in occupancy at the small scale. Turnover of entire P. basiramia networks occurred with average extinction and colonization rates of 1 shrub patch (0.8%) per year. Small-scale subpopulation extinction rate (77±15 gaps or 6.7% per year) was greater than colonization rate (26±2 gaps or 2.3% per year) and average abundance of plants in gaps decreased by 52%, indicating that the metapopulation is not at a stochastic steady state but is declining. Given that P. basiramia is locally common across its range, metapopulation decline is likely a short-term phenomenon due to the persistence of regional drought conditions during the early spring of 2000 and 2001. Since large-scale metapopulation dynamics are apparently in equilibrium, an examination of occupancy at this level alone would not have uncovered the dramatic local decline of P. basiramia. This study illustrates the importance of explicitly considering the spatial and temporal scales of metapopulation monitoring.
KEY WORDS: metapopulation dynamics, endemic plant, Florida scrub, gapology