Assessment of species limits among yellow-breasted meadowlarks (sturnella spp.) using mitochondrial and sex-linked markers

The yellow-breasted meadowlarks have endured more than a century of debate over species limits and patterns of diversity, ending with the current recognition of two species, the Eastern and Western meadowlarks (Sturnella magna and S. neglecta), by most authorities. Recently, it has been suggested that a form of the Eastern Meadowlark from the desert Southwest of the United States and northern Mexico is a distinct taxon, Lilian's Meadowlark (S. lilianae). We gathered sequence data from the mitochondrial genes cytochrome b and ND2 and from an intron of the sex-linked gene aconitase 1, from samples of all three forms from across their ranges. By genealogical concordance, these data strongly support the existence of three differentiated, historically isolated lineages. We recommend species recognition for S. lilianae (including the Mexican form auropectoralis), and note that its distributional limits in Mexico require clarification. Finally, we note that Z-linked nuclear markers may be particularly useful for lineage delimitation and phylogeny estimation in groups characterized by large variance in male reproductive success.