PARENT SESSION
Poster Session #73: Plant Demography.
Friday, August 9. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC

Comparative demography of two Florida scrub endemic plant species and their widespread congeners in relation to time-since-fire and gap size.

Maliakal, Satya^*,1, Menges, Eric², Denslow, Julie³, ¹ Louisiana State University, Baton Rouge, LA² Archbold Biological Station, Lake Placid, FL³ USDA Forest Service, Hilo, HI

ABSTRACT- The demography of species restricted to small ranges and specific habitats may be more sensitive to within-habitat environmental variation than co-occurring species that are more broadly distributed. We tested this hypothesis by comparing the demography of two pairs of congeners that differ in geographic range and habitat specificity but co-occur in the same habitat type: Florida rosemary scrub. We measured the density, survival, and growth of two narrowly endemic plants, Polygonella basiramia and Lechea cernua, specialists of open sand gaps in Florida rosemary scrub, in large and small gaps within rosemary scrub patches of three time-since-fire classes. We also measured the density, survival and growth of their widespread, habitat-generalist congeners, Polygonella robusta and Lechea deckertii, in relation to time-since-fire and gap-size. Densities of all species were higher in recently burned sites. Densities of L. cernua, P. basiramia, and P. robusta were significantly higher in larger gaps, whereas densities of L. deckertii were significantly higher in smaller gaps. Annual survival of L. cernua, L. deckertii, and P. robusta was highest in recently burned sites and lowest in long-unburned sites. Annual survival of P. basiramia did not differ with respect to time-since-fire. Gap size did not have a significant effect on survival of any species. Growth rates of all species were higher in recently burned sites, but did not differ with respect to gap size. Our results suggest that both time-since-fire and gap size have important effects on the demography of both the rosemary scrub specialist species and their widespread congeners. At least with respect to time-since-fire and gap size, demographic parameters of narrowly endemic plants were not consistently different from their widely distributed congeners.

KEY WORDS: plant demography, rare plants, comparative demography, Florida scrub