XVI International Botanical Congess

Sections and species complexes within Sphagnum are easy to recognize, but morphologically defined species within complexes are problematic. Nucleotide sequence variation in the ITS (nrDNA) and trnL (cpDNA) was used to assess the relationship between gene genealogies and morphological species in the sect. Acutifolia. Complexes of species (e.g., the S. capillifolium group) appear to be monophyletic (i.e., gene trees are congruent with presumed organismal relationships), but narrowly defined species within complexes are para- or polyphyletic. A complex of tropical American taxa form a monophyletic clade that appears to represent a relatively recent diversification from boreal species. No differentiation between North American and European populations is evident within the S. capillifolium complex. Many widespread bryophyte species may well prove to be para- or polyphyletic.