Abstract
Red‐cockaded woodpeckers (RCW; Dryobates borealis) declined after human activities reduced their fire‐maintained pine ecosystem to <3% of its historical range in the southeastern United States and degraded remaining habitat. An estimated 1.6 million RCW cooperative breeding groups declined to about 3,500 groups with no more than 10,000 birds by 1978. Management has increased RCW population abundances since they were at their lowest in the 1990s. However, no range‐wide study has been undertaken since then to investigate the impacts of this massive bottleneck or infer the effects of conservation management and recent demographic recoveries. We used mitochondrial DNA sequences (mtDNA) and nine nuclear microsatellite loci to determine if range‐wide demographic declines resulted in changes to genetic structure and diversity in RCW by comparing samples collected before 1970 (mtDNA data only), between 1992 and 1995 (mtDNA and microsatellites), and between 2010 and 2014 (mtDNA and microsatellites). We show that genetic diversity has been lost as detected by a reduction in the number of mitochondrial haplotypes. This reduction was apparent in comparisons of pre‐1970 mtDNA data with data from the 1992–1995 and 2010–2014 time points, with no change between the latter two time points in mtDNA and microsatellite analyses. The mtDNA data also revealed increases in range‐wide genetic differentiation, with a genetically panmictic population present throughout the southeastern United States in the pre‐1970s data and subsequent development of genetic structure that has remained unchanged since the 1990s. Genetic structure was also uncovered with the microsatellite data, which like the mtDNA data showed little change between the 1992–1995 and 2010–2014 data sets. Temporal haplotype networks revealed a consistent, star‐like phylogeny, suggesting that despite the overall loss of haplotypes, no phylogenetically distinct mtDNA lineages were lost when the population declined. Our results may suggest that management during the last two decades has prevented additional losses of genetic diversity.
Highlights
Most population genetic studies provide a snapshot of the current status of the species under investigation
Because of differences in sampling locations and sample sizes associated with the three Mitochondrial DNA (mtDNA) data sets described above, differentiation was calculated for various comparable partitions of the data similar to our analyses of genetic diversity
The availability of historical museum samples for use in retrospective comparisons with contemporary samples allows researchers to determine the extent of genetic changes that occur within a species over time
Summary
Most population genetic studies provide a snapshot of the current status of the species under investigation. Techniques for constructing artificial cavities in living pine trees were developed (Allen, 1991; Copeyon, 1990) as a means to sustain existing territories with natural cavity limitations and to create new viable territories at recruitment clusters, a management technique that has been highly successful in increasing the numbers of breeding groups in a population (Conner et al, 2001; Walters, Robinson, Starnes, & Goodson, 1995). The first and most recent range‐wide population genetic studies of RCWs were conducted in the early 1990s when population abundances were at their lowest (Haig, Belthoff, & Allen, 1993b; Haig, Bowman, & Mullins, 1996; Haig, Rhymer, & Heckel, 1994; Stangel, Lennartz, & Smith, 1992) These studies applied allozyme, DNA fingerprints, and randomly amplified polymorphic DNA (RAPD) markers and found low genetic diversity, especially in smaller populations. | 5423 whether management actions have had an impact on population genetic parameters
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