Genetic Variation and Population Structure of Red-cockaded Woodpeckers

Our objective was to survey genetic variability and examine population structure in the endangered Redcockaded Woodpecker, a species whose distribution has been fragmented by land-use patterns. Sixteen presumptive gene loci were resolved from feather pulp of nestlings and adults from 26 populations rangewide. Mean heterozygosity in the Red-cockaded Woodpecker was 7.8% and ranged from 3.1%-10.3% across populations. Heterozygosity was significantly but weakly associated with population size; this association was dependent on low heterozygosity in two small populations. The percentage of polymorphic loci and mean number of alleles per locus were also positively correlated with population size. Relative to other species of birds, there is a large among-population component of genetic variance (Fst = 0.14). Genetic distance among populations increased with geographic distance. Although heterozygosity is reduced in some small populations, most exhibit "normal" levels. Small populations should therefore not be considered "lost causes" from the genetic standpoint. Small populations are important as reservoirs of unique genetic combinations and to help facilitate gene flow among larger populations.