Systematics of the Menidia beryllina Complex (Pisces: Atherinidae) from the Gulf of Mexico and Its Tributaries

The Menidia beryllina complex from the Gulf of Mexico and Gulf slope drainages includes those forms referred to M. audens, M. beryllina, M. beryllina atrimentis, M. beryllina peninsulae, M. peninsulae and M. peninsulae atrimentis. The relationship between the Mississippi Valley form (M. audens) and the coastal form (M. beryllina) is clinal for several purportedly diagnostic characters, and within populations, character variation is often large and differences between size classes are noted. Variation of the M. beryllina phenotype is also found in other rivers. The relationship between M. beryllina and M. peninsulae has been obscured by historical treatment. Menidia peninsulae, from Florida to Tamiahua, Mexico, can be distinguished by several morphometric and vertebral characteristics. We conclude that M. audens, M. beryllina atrimentis and M. peninsulae atrimentis are synonyms of M. beryllina and that M. peninsulae is a distinct species; a redescription of M. peninsulae is included.