Population genetic structure of the American oystercatcher in Northwestern Mexico

Abstract Assessments of genetic diversity and population structure are essential for defining management units to prioritize conservation and management efforts. A susbspecies of the American oystercatcher ( Haematopus palliatus frazari ) breeds in northwestern Mexico and is endangered due to its small population size, restricted distribution, and high vulnerability to anthropogenic activities. This study analyzed the genetic diversity and population structure of the American oystercatcher in six areas in northwestern Mexico. We used two molecular markers, the mtDNA control region and single nucleotide polymorphisms (SNPs), to calculate genetic diversity, population structure, the kinship coefficient, and migration rates among these geographic areas. Genetic diversity was high when calculated using mtDNA (h = 0.689) and relatively high for SNPs (h = 0.222). We identified genetic structure across geographic areas based on 1,889 SNPs. Individuals from the Baja California peninsula were genetically differentiated from those of the Sonora and Sinaloa populations. Indeed, the population of the Baja California peninsula can be considered a distinct demographic unit. This may be explained by high philopatry (low dispersal and recruitment of breeders) and regional habitat discontinuity (Sonora and Sinaloa were similar but different from the Baja California peninsula). Of note, the Bahia Santa María (Sinaloa) population serves as a source of individuals to other populations in the region. We recommend that conservation efforts prioritize major concentration sites, such as Bahia Santa María (Sinaloa), while also protecting smaller, isolated demographic units, such as the populations of Bahia de la Paz (Baja California Sur) and Bahia de Ceuta (Sinaloa).