Geographical variation in the breeding cycles and recruitment of Patella spp.

Abstract

The effect of geographical differences in breeding cycles on the recruitment variation of the limpets — Patella vulgata L., P. aspera Röding and (to a limited extent) P. depressa Pennant — has been studied over much of their range in Britain and NW. Europe. In spite of considerable annual and local variation in recruitment success, broader patterns can be distinguished, which can be linked to spawning times and factors affecting the survival of newly-settled spat. The breeding cycles of P. vulgata and P. aspera differ across their ranges in that, in both species, spawning begins, and gametogenesis ends, earlier in the north and east than in the south and west. The cause of these differences can be correlated with geographical and annual differences in sea temperature over the potential breeding periods, and can be related to the regional incidence of conditions found experimentally to be necessary for successful settlement and survival of spat during a critical stage of their growth. The significance of this ‘temperature window’ in determining the littoral and geographical distribution of the species is discussed.