USDA Forest Service

Pacific Southwest Research Station

Pacific Southwest
Research Station

800 Buchanan Street
Albany, CA 94710-0011
(510) 883-8830
United States Department of Agriculture Forest Service. USDA logo which links to the department's national site. Forest Service logo which links to the agency's national site.

Biodiversity and Conservation Biology

F. Thomas Ledig

My research is primarily in conservation genetics and evolutionary biology, specifically, (1) the conservation genetics and mating systems of rare Mexican spruces and pinyon pines, (2) the recent evolutionary history and biogeography of Californian conifers, and (3) the response of pines to global warming using pitch pine, a species native to the eastern U.S., as a model. We use isozymes and common garden tests to investigate natural populations of forest trees. In the conservation of plant species, the choice to protect or neglect often depends on taxonomic status, and our research frequently begins with phylogenetic questions and proceeds to studies of genetic structure and mating systems. We reconstruct evolutionary history and determine the processes (selection, mutation, genetic drift, migration) that shape a species' genetic structure. The objective is to develop principles for the conservation of biodiversity, often based on studies of the genetic structure of rare endemics which serve as models for more widespread species fragmented by loss of habitat.

Conservation biology of rare and endemic species
  • Phylogeny and diversity in the southwestern white pine-Mexican white pine complex.
  • Effects of fragmentation on various endemic species, including Mexican spruces and Pacific Coast endemics, such as Santa Lucia fir, Brewer spruce, and Coulter pine.
  • Biogeography and the effects of migration during global warming on the genetic structure of the big-cone pines.
  • Evolution and genetic structure of several Californian and Mexican conifers as an aid to conservation.
Adaptation and adaptability
  • Adaptability in pitch pine, Coulter pine, Torrey pine, and other tree species in common garden tests.
  • Reproductive trade-offs and the extension of 'clutch size' hypotheses to conifers.
  • Changes in springwood/summerwood ratio in pitch pine as a result of climate change.
Relationship of genetic diversity to developmental stability and viability
Bristlecone pines
  • Effect of genetic diversity on survival and fitness surrogates in sugar pine, Coulter pine, and pitch pine.
  • Population homeostasis, individual heterozygousity, and developmental stability in Coulter pine.
  • Effect of the injection of diversity on fitness in Torrey pine.
Origin of genetic variation in long lived perennials
  • Origin of diversity by somatic mutation in bristlecone pine.
  • The production of novel alleles, or hybrizymes, in the F2 and backcrosses of the Jeffrey x Coulter pine hybrid.

These approaches provide insights into ecosystem dynamics, and suggest new approaches for management of forests.

Studies range from regional to international in scope. Cooperators in México include: Colegio de Postgraduados en Ciencias Agricolas, Montecillo; Universidad Autónoma Agraria Antonio Narro, Saltillo; Instituto de Investigaciónes sobre los Recursos Naturales, Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Michoacan. Other cooperators are: CAMCORE, Raleigh, NC; International Programs, USDA Forest Service, Washington, DC.

FAO North American Forest Commission