XVI International Botanical Congess
Bryophyte taxonomy has traditionally been based strictly on morphological characters, although ordinary means of separating species routinely include microscopic features. In this century, the trend has been for bryophyte taxonomists to lump many species that were originally described by authors of local floras. Thus, species of mosses and liverworts commonly have very wide ranges, many are intercontinentally disjunct. Recent evidence from molecular genetic markers, however, suggests that these isolated sets of populations are sometimes strongly genetically differentiated, and more careful examination reveals morphological and ecological differences as well. Moreover, some recent studies of liverworts and mosses have detected strong genetic divergence even within areas of sympatry. These cryptic species pose a challenge to traditional bryophyte taxonomy. A collision of worldviews appears imminent.