A study of Scirpus acutus and Scirpus validus in the Saskatchewan River delta

Abstract

A study of Scirpus populations (section Pterolepis) in the Saskatchewan River Delta was conducted to examine morphological and ecological characters of the Scirpus acutus Muhl. and S. validus Vahl complex to determine whether or not they should be differentiated as species.Population collections from stands of Scirpus and stands of suspected clonal hybrids were taken in 1966 and 1968 from various locations within the delta of the Saskatchewan River. Environmental data such as water depths were recorded at time of collection.Two morphologically and ecologically distinct groups emerged; their hybrids were sterile or nearly so. The features of panicle ray length and floral scale length: achene length ratio were found to be diagnostic morphological criteria for separating the Scirpus examined into two sets of distinct populations. These two sets of populations differed ecologically in terms of water depth tolerances: the S. acutus type tolerates between 60 and 150 cm, whereas the S. validus type occurs only at depths less than 65 cm.It was concluded that in the geographic area in which they were studied, these two separate populations would best be regarded as separate species.