New approaches to the systematics of liverworts
Bischler, Helene; Boisselier-Dubayle, Marie-Catherine
Species are a practical necessity. Morphological data alone often prove to be insufficient for unambiguous identification of taxonomic units. We attempted to clarify the delimitation of some taxonomically controversial species or groups of taxa in combining morphological data, chromosome counts and information from molecular markers. In some Marchantialean species, morphological variation considered to be diagnostic was found to have no genetic background, in others, haploid and polyploid sibling taxa were detected. Unknown polyploids and interspecific hybrids were discovered in both the Marchantiales and Jungermanniales. Allopolyploidy must be recognized as an important process in liverwort evolution. Moreover, similar morphological patterns appear to be maintained, with or without genetic diversification, between intercontinentally disjunct conspecific populations in the Marchantiales. This morphological stability remains unexplained. More research linking morphology to population biology is needed to confirm the genetic coherence of taxonomic liverwort species.