Bachman\u27s Sparrow (Peucaea aestivalis) population structure across the southeastern USA

Understanding gene flow and population structure in wildlife populations helps managers to protect distinct genetic lineages and genetic variation in small, isolated populations at high risk of extinction. I assessed genetic diversity in Bachman’s Sparrows (Peucaea aestivalis) to evaluate the role of natural barriers in shaping evolutionarily significant units as well as the effect of anthropogenically-caused habitat loss and fragmentation on population differentiation and diversity. Genetic diversity was assessed across the geographic range of Bachman’s Sparrow by genotyping 226 individuals at 18 microsatellite loci and sequencing 48 individuals at nuclear and mitochondrial DNA genes. Multiple analyses consistently demonstrated high levels of gene flow, which appear to have maintained high levels of genetic variation and panmixia in populations throughout the species’ range. Based on these genetic data, separate management units/subspecies designations or artificial gene flow among populations in habitat fragments do not seem necessary. High vagility in Bachman’s Sparrow may be an adaptation to colonize ephemeral, fire-mediated longleaf pine habitat, but in recent times, it also appears to have reduced inbreeding and loss of genetic diversity in habitat fragments

Adaptation to ephemeral habitat may overcome natural barriers and severe habitat fragmentation in a fire-dependent species, the Bachman\u27s Sparrow (Peucaea aestivalis)

Bachman\u27s Sparrow (Peucaea aestivalis) is a fire-dependent species that has undergone range-wide population declines in recent decades. We examined genetic diversity in Bachman\u27s Sparrows to determine whether natural barriers have led to distinct population units and to assess the effect of anthropogenic habitat loss and fragmentation. Genetic diversity was examined across the geographic range by genotyping 226 individuals at 18 microsatellite loci and sequencing 48 individuals at mitochondrial and nuclear genes. Multiple analyses consistently demonstrated little genetic structure and high levels of genetic variation, suggesting that populations are panmictic. Based on these genetic data, separate management units/subspecies designations or translocations to promote gene flow among fragmented populations do not appear to be necessary. Panmixia in Bachman\u27s Sparrow may be a consequence of an historical range expansion and retraction. Alternatively, high vagility in Bachman\u27s Sparrow may be an adaptation to the ephemeral, fire-mediated habitat that this species prefers. In recent times, high vagility also appears to have offset inbreeding and loss of genetic diversity in highly fragmented habitat. © 2014 Cerame et al

Factorial correspondence analysis of 226 Bachman's Sparrow individuals from eleven study populations.

<p>Population abbreviations are as follows: Abita Springs (AS), Avon Park (AP), Dry Prong (DP), Fort Polk WMA (FP), Kisatchie National Forest (KNF), North Carolina (NC), Palustris Experimental Forest (PEF), Sandy Hollow WMA (SH), Tall Timbers Research Station (TTRS), Talisheek Pine Wetlands Preserve (TNC), Camp Whispering Pines (WP).</p

Bachman's Sparrow distribution including historic range expansion and subspecific ranges.

<p>Ranges as described by the AOU <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0105782#pone.0105782-AOU1" target="_blank">[21]</a> and Dunning <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0105782#pone.0105782-Dunning1" target="_blank">[74]</a>. Sampling locations include: Fort Polk WMA (FP), Palustris Experimental Forest (PEF), Kisatchie National Forest (KNF), Dry Prong WMA (DP), Camp Whispering Pines (WP), Sandy Hollow WMA (SH), Talisheek Pines Wetland Preserve (TNC), Abita Springs (AS), Tall Timbers Research Station (TTRS), Avon Park Air Force Range (AP), and North Carolina (NC).</p

AMOVA results using mitochondrial ND2 and nuclear TGFβ2 sequences from five regional Bachman's Sparrow populations.

<p>AMOVA results using mitochondrial ND2 and nuclear TGFβ2 sequences from five regional Bachman's Sparrow populations.</p

STRUCTURE plot with LocPrior for K = 2 populations.

<p>Each column represents an individual, each color denotes a population cluster. Population abbreviations are as follows: Abita Springs (AS), Avon Park (AP), Dry Prong (DP), Fort Polk WMA (FP), Kisatchie National Forest (KNF), North Carolina (NC), Palustris Experimental Forest (PEF), Sandy Hollow WMA (SH), Tall Timbers Research Station (TTRS), Talisheek Pine Wetlands Preserve (TNC), Camp Whispering Pines (WP).</p

Pairwise estimates of F_ST (below diagonal) and R_ST (above diagonal) for eleven populations, arranged from west to east.

<p>Significant p-values (p≤0.05) indicated in bold. DP  =  Dry Prong, FP  =  Fort Polk, KNF  =  Kisatchie National Forest, PEF  =  Palustris Experimental Forest, WP  =  Camp Whispering Pines, SH  =  Sandy Hollow, TNC  =  Talisheek Pine Wetlands Preserve, AS  =  Abita Springs, TTRS  =  Tall Timbers Research Station, AP  =  Avon Park, NC  =  North Carolina.</p><p>Pairwise estimates of F_ST (below diagonal) and R_ST (above diagonal) for eleven populations, arranged from west to east.</p

Mean of estimated ln probability of data using LocPrior in Structure for K = 1–11.

<p>Using Structure Harvester, the most likely K = 2.</p

Results of migrant detection analysis in GENECLASS showing individuals with significant assignment probabilities (p<0.01) for population origins other than the study site in which they were sampled.

<p>Results of migrant detection analysis in GENECLASS showing individuals with significant assignment probabilities (p<0.01) for population origins other than the study site in which they were sampled.</p

Genetic diversity at ND2 and TGFβ2 for five regional Bachman's Sparrow populations including sample size (n), nucleotide diversity (π), number of haplotypes, and haplotype diversity with standard deviation.

<p>The western Louisiana grouping includes Fort Polk WMA, Dry Prong, Kisatchie National Forest and Palustris Experimental Forest sampling locations. The eastern Louisiana grouping includes Camp Whispering Pines, Sandy Hollow WMA, Abita Springs, Talisheek Pines Wetlands Preserve and Lee Memorial Forest. Northern Florida is the Tall Timbers Research Station and southern Florida is the Avon Park Air Force Range.</p><p>Genetic diversity at ND2 and TGFβ2 for five regional Bachman's Sparrow populations including sample size (n), nucleotide diversity (π), number of haplotypes, and haplotype diversity with standard deviation.</p