Red-cockaded woodpeckers (RCW) have been on the federal list of endangered species since 1975, primarily due to habitat destruction and fragmentation that reduced RCW population sizes by 99% over the past century. In recent decades, the Department of Defense (DoD) has provided extensive support for RCW research, monitoring, and management on its extensive longleaf-pine (Pinus palustrus) forest holdings. By addressing the hypothesis that genetic structure of RCW has not changed over time, this project provided an updated view of the species over the past 100 years. Researchers determined the effects that translocations of birds among populations have had on their population genetics and examined the long-term effects of forest fragmentation on changes in genetic differentiation and diversity across the species.

Researchers used a multidisciplinary approach that integrated population genetics (i.e., microsatellite markers and mitochondrial DNA sequences), ancient DNA techniques, and landscape ecology in a manner that permitted a better understanding of the status of RCW populations, particularly those that have been monitored and managed on DoD land for over three decades. Existing data on translocation histories, and habitat loss throughout the southeast was used to identify factors that affected RCW genetics, historically and in modern times.

The project team used mitochondrial DNA sequences (mtDNA) and nine nuclear microsatellite loci to determine if demographic declines across the range of RCW was associated with changes in genetic structure and diversit over time. The project team compared samples collected before 1970 (mtDNA data only), between 1992 and 1995 (mtDNA and microsatellites), and between 2010 and 2014 (mtDNA and microsatellites). The analyses revealed that genetic diversity had been lost, as reflected by a reduction in the number of mitochondrial haplotypes. This change was observed in comparisons of pre‐1970 mtDNA data with data from the 1992–1995 and 2010–2014 time points; no change between the latter two time points in mtDNA and microsatellite analyses was detected. The mtDNA data also revealed increases in range‐wide genetic differentiation. No evidence for genetic differentiation of populations was identified in the pre-1970’s data set, indicating that a genetically panmictic population existed. By contrast, genetic structure and subdivided populations were identified and appeared to be unchanged after the 1990’s. Similar results were noted with the microsatellite data set, which revealed little change between the 1992–1995 and 2010–2014 time points. Comparisons of haplotype networks over time revealed a consistent star‐like phylogeny, indicating that, despite the overall loss of haplotypes, no phylogenetically distinct mtDNA lineages were lost when the population declined. The results may suggest that management actions since the 1990’s, including translocations, has prevented additional losses of genetic diversity.

The outcomes from this project included an updated assessment of the genetic status of RCW that includes an assessment of changes over time. Insights included evaluations of the roles that translocations and other management actions have had in preserving or enhancing genetic diversity within and among populations. Researchers also provided DoD and other biologists guidance to help them evaluate the pros/cons of potential movements of birds based on relative comparisons of genetic diversity among different populations in order to maintain the healthiest populations possible.