Data for: Surrounding landscape, habitat and hybridization dynamics drive population structure and genetic diversity in the Saltmarsh Sparrow (Ammospiza caudacuta)

Determining factors that shape a species’ population genetic structure is beneficial for identifying effective conservation practices. We assessed population structure and genetic diversity for Saltmarsh Sparrow (Ammospiza caudacuta), an imperiled tidal marsh specialist, using 13 microsatellite markers and 964 individuals sampled from 24 marshes across the breeding range. We show that Saltmarsh Sparrow populations are structured regionally by isolation-by-distance, with gene flow occurring among marshes within ~110-135 km of one another. Isolation-by-resistance and isolation-by-environment also shape genetic variation; several habitat and landscape features are associated with genetic diversity and genetic divergence among populations. Human development in the surrounding landscape isolates breeding marshes, reducing genetic diversity and increasing population genetic divergence, while surrounding marshland and patch habitat quality (proportion high marsh and sea-level-rise trend) have ..., Saltmarsh Sparrows (n = 964) were sampled from 24 marshes along the northeastern coastline of the United States over a nine-year period, between 2007-2015 (Figure 1; Table S1). Sampling covered approximately 60% of the global breeding range of Saltmarsh Sparrows, with sites in Maine (n = 6), New Hampshire (n = 4), Massachusetts (n = 2), Rhode Island (n = 2), Connecticut (n = 3), New York (n = 5), and New Jersey (n = 2). A portion of the samples analyzed in this study were collected in 2007 – 2008 for a study evaluating fine-scale genetic structure in Saltmarsh Sparrows in the northern portion of their range (Walsh et al. 2012) and in 2012 – 2013 while studying patterns of introgression between Saltmarsh Sparrows and their sister species, the Nelson’s Sparrow (Walsh et al. 2015). The majority of the remaining samples were collected during a three-year (2011 – 2013) study investigating survival and fecundity of Saltmarsh Sparrows (Ruskin et al., 2017a,b, Field et al. 2017b). We captured a...,