Evolutionary Institution of Oceanogra s Palmas,

of two other species of Arbacia, and our data show that it is hybridizing with one of limited overlap in the subtropics. This separation has tropical sea urchin genus contains species in more than et al. 1997). An alternate route around the southern tip Present address: Science Applications International Corporation, MD, USA. Molecular Ecology (2012) 21, 130–144 doi: 10.1111/j.1365-294X.2011.05303.ximportant biogeographical consequences, because one ocean, because such contacts were possible in the past. The Tethys Sea in the Northern Hemisphere had connected the Indo-Pacific with the Atlantic until th