Genome-wide assessment of population structure in Florida’s coastal seaside sparrows

The distribution and genetic relatedness of subspecies among the populations of seaside sparrow (Ammospiza maritima [Wilson 1810]) along the coast of Florida are poorly understood. We evaluated genetic support for three defined Florida Gulf coast subspecies, as well as a fourth subspecies on the Atlantic coast, and assessed whether genetic clusters corresponded geographically with the defined ranges of subspecific designations. Data generated using double digest restriction site-associated DNA sequencing (ddRADseq) suggest that the Florida endemics, A. m. peninsulae and A. m. juncicola, are genetically indistinguishable, but that the third Gulf coast subspecies, A. m. fisheri, and the Atlantic coast subspecies, A. m. macgillivraii, are genetically distinct units. These three distinct genetic groups were identified in three main geographic areas within the state of Florida, USA: (1) Florida’s panhandle (2) Florida’s Gulf coast peninsula, and (3) the Atlantic coast. Admixture was detected between genetic clusters in sites near the transition zone between the Florida panhandle and peninsula. Geographic distributions of genetic clusters on the Gulf coast do not match currently defined subspecific ranges for A. m. fisheri and A. m. peninsulae.