Genetic variability of Acartia tonsa (Crustacea: Copepoda) on the Brazilian coast

Marine plankton is characterized by a large number of populations and their potential for dispersal by ocean currents, although it is unclear whether they may represent the same species or a number of different cryptic species. A number of studies have detected genetic structuring over a range of spatial scales, including ocean basins, gyres within the same ocean basin and, regionally, among coastal features such as estuaries and inlets (Goetze, 2003; Blanco-Bercial et al., 2011; Chen and Hare, 2011). Patterns of genetic structuring may also vary between holoplanktonic species from the same site (e.g. Eucalanus hyalinus vs. Eucalanus spinifer; Goetze, 2005). The calanoid copepod Acartia tonsa, a species described more than 150 years ago, is seasonally dominant in many coastal and estuarine environments in the Atlantic and Indo-Pacific (Mauchline, 1998). Recent genetic analyses