Population genetics of a snail species complex in the British Isles: Littorina saxatilis (Olivi), L-neglecta bean and L-tenebrosa (Montagu), using SSCP analysis of cytochrome-B gene fragments

The intertidal snail Littorina,saxntilis displays a range of shell morpholo gies associated with a variety of habitats. Since morphology has an environ mental and genetic basis, shell-based taxonomy may not accurately reflect g enetic relationships. We explored genetic structure among adjacent populati ons of L. saxatilis (the robust open-shore type). L. neglecta (the tiny bar nacle-dwelling type) and L. tenebrosa (the fragile brackish-water type), at nine sites in Britain. Using single-strand conformational polymorphism ana lysis of a 375bp fragment of cytochrome-b we found no evidence of species d istinction. In AMOVA tests significant variation was contained among popula tions (68%;,) and among individuals (32%, both P < 0.001), and insignifican t variation was found among ecotypes. Genetic patterns suggested gene flow among ecotypes over small scales and a strong random input over larger scal es.