Rebecca Dolan is interested in patterns of genetic variation in plants and how they influence, and are influenced, by rarity. Following initial descriptive studies of overall isozyme variation in a suite of Florida’s scrub endemics, she investigated local scale patterns of genetic variation in Hypericum cumulicola during 1999-00. This species shows strikingly high differentiation between populations, indicating little current gene flow. Fire, an important restorative management practice in scrub vegetation, kills most mature plants but results in a flush of seed germination from a persistent seed bank. At two sites on the southern Lake Wales Ridge, Dolan and Archbold colleagues Eric Menges and Pedro Quintana-Ascencio (see pages 6-8) will be examining the dynamics of genetic change that this turnover in aboveground plants produces. Does the wholesale mortality of aboveground individuals force the population through a genetic bottleneck? Or does this allow expression of genetic traits stored in the soil seed bank? The work is funded by the Florida Division of Forestry.

During a sabbatical year (1998-99) at Archbold, Daniel Gagnon initiated a research project with Eric Menges and Carl Weekley on the annual soil moisture patterns affecting endangered endemic perennials of the Florida scrub. Soil moisture patterns of three scrub communities (rosemary scrub, scrubby flatwoods, hickory scrub) have been monitored continuously since October 1998. We found that higher soil moisture is associated with recent fire (reduction in transpiring plant biomass). During winter dry spells, gaps (see also; Gapology, page 8) in shrub cover have higher soil moisture than under shrub cover. These results support the hypothesis that one of the ways that fire is favorable to many scrub endemic perennials is by the increase in soil moisture after a fire has reduced the biomass of the larger shrub competitors. Many endemic perennials are found almost exclusively in gaps, and their populations decline with increasing time since fire. The higher soil moisture in gaps after a fire may be a critical factor for seedling recruitment of these species. Eric Menges is concurrently measuring pre-dawn water potential on two common shrubs and three endangered herb species to verify that low soil moisture correlates with water stress in the vegetation.

Doria Gordon continued to work with Hilary Swain and Eric Menges and collaborators. Together they worked on manuscripts from projects discussed in the previous Biennial Report. Gordon, Swain, and Leonard Brennan (Tall Timbers Res. Sta.) developed a manuscript from their effort to identify the highest priority research needs for conservation of biodiversity in Florida. The database of questions, organized by theoretical and management topic and priority, is now accessible on the Internet <http://www.TallTimbers.org/research/fcbrpdata.html>. The most interesting findings are that: 1) applied conservation research needs are a fairly narrow subset of the broader theoretical research agenda for biodiversity; and 2) much of the research needed can be integrated with existing management and will not need extra funding for treatment application. Additionally, Gordon is completing a manuscript on the demography and population viability of one of the seven rare scrub endemic plant species that she, Menges, and Rebecca Dolan investigated. Several papers are underway or have been produced from this project.