Molecular phylogenetics of the Neanthes acuminata (Annelida: Nereididae) species complex

Reish, D.J., Anderson, F.E., Horn, K.M. and Hardege, J. 2014. Molecular phylogenetics of the Neanthes acuminata (Annelida: Nereididae) species complex . Memoirs of Museum Victoria 71: 271-278. The Neanthes acuminata (Nereididae) species complex is a broadly distributed group of marine benthic polychaetous annelids that is known by many names around the world and comprises at least four species. They are the only nereidids known that show exclusively male parental care. The female dies after laying her eggs in a common mucoid tube where they are fertilized, and the male incubates the eggs until the young leave the tube. All of the species in the N. acuminata complex are identical in their morphological characteristics and they all possess a similar number of segments and paragnath distribution and similarly shaped parapodia. However, populations from the U.S. East Coast, southern California, Hawaii and Portugal differ in chromosome number. Eye and egg colour also vary among populations—some worms in southern California have red eyes and produce bright yellow/orange eggs, while others have black eyes and produce pale yellow eggs. These variations suggest that N. acuminata may represent multiple evolutionarily significant units. Clarification of the phylogenetic relationships among lineages in this species complex will provide a framework for studying character evolution and revising taxonomy within this intriguing group of nereidids. To that end, we sequenced regions of one nuclear and two mitochondrial genes from worms sampled from multiple sites in North America (southern California, Mexico and Connecticut), the central Pacific (Hawaii) and Europe (Germany, Portugal and the UK). Maximum likelihood and Bayesian analyses of these data clarify relationships in this complex and show that worms sampled from California and Mexico represent two geographically intermingled subclades. These two subclades are congruent with eye and egg colour data; one subclade consists of red-eyed worms, the other consists of black-eyed worms. Furthermore, we found evidence that individuals representing these subclades can occasionally be found at the same locality.