Spatial and environmental components of evolutionary change: interactive effects of salinity and temperature on Fucus vesiculosus as an example

Abstract

Intertidal algae experience aerial temperatures as well as those of ambient seawater and, during their periods of emergence, are subject to considerable variation in salinity. The eastern Atlantic distribution of Fucus vesiculosus L. (Phaeophyta) lies within the 5° and 20° August isotherms. Experiments indicate that this plant can survive temperatures above and below these at normal salinity (34‰). However, at extreme temperatures it is evidently much more susceptible to saline changes than at those of the limiting isotherms. Thus the temperature limits for surviving acute saline change appear to give a better biogeographical fit than temperature alone. Nevertheless, the presence of F. vesiculosus in estuaries at or near both geographical limits is inconsistent with the experimental results obtained from British plants. Some population divergence may therefore have occurred. © 1987 Biologische Anstalt Helgoland.