Patterns of Variation in Sphagnum capillifolium Sensu Lato

Abstract

Complex patterns of morphological variation within Sphagnum capillifolium sensu lato have led to a confusing array of taxonomic treatments. An exploratory investigation was undertaken of the variation within a single peatland. Results of a multivariate analysis of a random sample of the population indicates that two taxa, a woodland taxon corresponding to S. subtile (Russow) Warnst. and an open bog taxon corresponding to S. rubellum Wils., may be recognized. Both taxa remained distinct in a common garden without any evidence of intergradation between them. These results are significant since S. subtile has been viewed by some taxonomists as a taxon of doubtful value. It is recommended that S. subtile deserves taxonomic recognition although further investigations are desirable to determine the taxonomic status of these and other taxa in S. ca- pillifolium sensu lato since this investigation was limited to a single peatland. Sphagnum capillifolium (Ehrh.) Hedw. is one of the most common species ofpeatmoss in the Sphag- num-dominated peatlands of northeastern North America and Eurasia (Crum 1975). Variation with- in the species appears to correspond to the vertical gradient of the hummock-hollow complex. Crum (1975, 1984) cites the variation of this species as an example of the stem leaves that vary in the direction of branch leaves in shape and structure. Small plants comprising the mat, small hummocks, and the base and sides of larger hummocks of many open bogs are referred to var. tenellum (Schimp.) Andr. while larger plants comprising large dry hummocks in open bog and woodland habitats are referred to var. ca- pillifolium (Ehrh.) Hedw. Vitt, Crum, and Snider (1975) reported var. tenellum growing above var. capillifolium in the general Sphagnum hummock- hollow sequence, but later admitted that they had the concepts of these varieties reversed (Andrus et al. 1984). Although there is no evidence indicating a genetic basis for the variation, Crum (1975, 1984) believes that the variation is consistent enough throughout the range of the species to justify taxo- nomic recognition. However, Hill (1976, 1978) maintains that intermediates are too common for