9423662 EANES The dynamics of speciation in wide-ranging and widely dispersing organisms continues to challenge evolutionary biologists, especially in marine invertebrates where geographic isolation seems unlikely in many cases. Recent work suggests that the molecular interaction of sperm and eggs may play a major role in reproductive isolation in animals that release gametes freely into the water. In sea urchins in particular, a molecule (the protein "bindin") has been characterized that mediates species specific fertilization. DNA-techniques now permit us to examine the forces that underlie the evolution of this reproductive barrier, and the consequences for fitness can be easily studied in sea urchins. The free spawning echinoids Strongylocentrotus droebachiensis and S. pallidus are close relatives of a major model organism in cellular and developmental biology, S. purpuratus. They co-occur throughout northern high latitudes and may hybridize asymmetrically. This study will examine their population structure and the evolution of their bindin-molecules at the DNA level. Preliminary data show geographic differentiation and interesting patterns of molecular evolution. The project will also add to the scarce data on the population structure and dynamics of circumarctic species. This is particularly important for S. droebachiensis which is being harvested increasingly.
