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Abstract

Understanding species boundaries is a fundamental, but challenging, component of describing and understanding the generation and maintenance of biodiversity. Examining differences among very recently diverged populations can provide insight into the traits and evolutionary mechanisms that drive divergence. The genus Sturnella includes two recently diverged species, the Eastern (Sturnella magna) and Western (S. neglecta) Meadowlark, the former of which has a complex of subspecies distributed across the Americas. Of the Eastern Meadowlark subspecies that occur in the U.S., S. m. lilianae is the only one with a disjunct range in the southwestern U.S. and central Mexico. It also has markedly different song patterns than all other Eastern Meadowlark subspecies. In order to assess population differentiation, we performed whole genome sequencing of 35 birds as well as analysis of various song characteristics, including maximum and minimum frequencies. Results were visualized using principal component analyses and analyzed by running linear discriminant function analyses. S. m. lilianae exhibits high levels of genetic and vocal differentiation from both the Eastern Meadowlark and the Western Meadowlark, and likely forms a distinct evolutionary lineage. Additionally, the subspecies S. m. auropectoralis shows no genetic or acoustic differentiation from S. m. lilianae, suggesting that the subspecies falls within the lilianae group and not the magna group.