Adrienne I. Kovach

Eco‐phylogeographic approaches to comparative population genetic analyses allow for the inclusion of intrinsic influences as drivers of intraspecific genetic structure. This insight into microevolutionary processes, including changes within a species or lineage, provides better mechanistic understanding of species‐specific interactions and enables predictions of evolutionary responses to environmental change. In this study, we used single nucleotide polymorphisms (SNPs) identified from reduced representation sequencing to compare neutral population structure, isolation by distance (IBD), genetic diversity and effective population size ( N e ) across three closely related and co‐distributed saltmarsh sparrow species differing along a specialization gradient—Nelson's ( Ammospiza nelsoni subvirgata ), saltmarsh ( A. caudacuta ) and seaside sparrows ( A. maritima maritima ). Using an eco‐phylogeographic lens within a conservation management context, we tested predictions about species' degree of evolutionary history and ecological specialization to tidal marshes, habitat, current distribution and population status on population genetic metrics. Population structure differed among the species consistent with their current distribution and habitat factors, rather than degree of ecological specialization: seaside sparrows were panmictic, saltmarsh sparrows showed hierarchical structure and Nelson's sparrows were differentiated into multiple, genetically distinct populations. Neutral population genetic theory and demographic/evolutionary history predicted patterns of genetic diversity and N e rather than degree of ecological specialization. Patterns of population variation and evolutionary distinctiveness (Shapely metric) suggest different conservation measures for long‐term persistence and evolutionary potential in each species. Our findings contribute to a broader understanding of the complex factors influencing genetic variation, beyond specialist‐generalist status and support the role of an eco‐phylogeographic approach in population and conservation genetics.

Saltmarsh ( Ammospiza caudacuta ) and Nelson's ( A. nelsoni ) sparrows are sister taxa that breed in tidal marshes along the coast of the Northeastern United States and Canada. The Saltmarsh Sparrow breeds from mid‐coast Maine south to Virginia, while the Acadian Nelson's Sparrow breeds from the Canadian maritime provinces south to northern Massachusetts. Here, we present three extralimital observations of breeding Saltmarsh ( n = 2) and Nelson's ( n = 1) sparrows. In 2021 and 2022, we observed Saltmarsh Sparrow females attending nests at Mendall Marsh, ME, and Milbridge, ME, respectively, approximately 60 and 110 km beyond the documented northern extent of the Saltmarsh Sparrow breeding range. In 2022, we observed a breeding‐condition male Nelson's sparrow singing in the upriver portion of a marsh on Cape Cod, Massachusetts, approximately 115 km beyond the previously documented southern extent of the Nelson's Sparrow breeding range. We confirmed morphological species identification using a panel of microsatellite DNA loci. Due to both the well‐documented population declines of these species in the region and the intensity of sampling effort undertaken in recent years, we suggest that these observations likely are not indicative of range expansion. However, they do indicate that these 2 taxa have the capacity to use and successfully reproduce in marshes well beyond their established breeding limits. Our findings provide novel insight into the potential for these taxa to occur and successfully breed outside their documented breeding ranges. Given increased interest in their conservation, these results support the idea that management actions aimed at creating or maintaining nesting habitat across both species ranges could benefit both taxa.