Molecules and morphology: conflicts and congruence within the fern genus Trichomanes (Hymenophyllaceae)

The interaction between three independent data sets (anatomy/morphology, cytology, molecules) has been evaluated within the controversial genus Trichomanes (Hymenophyllaceae). Anatomy/morphology, cytology, and rbcL sequences, despite their high and significant level of incongruence, were thus empirically combined with differential weighting in a cladistic analysis within Trichomanes in order to give an appreciation of the contribution of each data set in the resulting topologies and to study more precisely the nature of potential conflicts. Results show that any standard statistics values (such as bootstrap) do not appear to be objectively useful for the choice of the "best" topology or the "good" clades provided by the combination. This weighting approach reveals three cases: (i) some clades (such as subgenus Didymoglossum) are always retrieved and correspond to the absence of conflicts between the different data, (ii) some new clades (such as subgenus Achomanes) are either provided or reenforced as a "synergetic" result of the combination of the data and (iii) that remaining conflicting clades reflect the persistence of incongruence between data whatever the weighting.