Ecogeographical tolerance range variation in aquatic macrophytes

A portion of central Canada (area B) and a smaller, soft-water area within it on the Precambrian Shield (area A) were surveyed for aquatic macrophytes in relation to eight water chemistry parameters. pH, total dissolved solids and total alkalinity appeared to be the three most important factors correlated with macrophyte distribution. T-tests indicated that species for which water chemistry affinities were not discrepant in areas A and B could be identified as specialized or unspecialized plants with respect to area A. Other species behaved quite differently in the two areas. In most cases for pH and dissolved inorganics macrophytes showed lower mean values and lower upper tolerance range limits in area A than in area B, reflecting the prevailing water chemistry values in the two areas. These results suggested that adaptation had occurred in one or both sets of populations. A number of interspecific associations were demonstrated in area A, many of which coincided with similarities in water chemistry affinities.