On the occurrence of asymmetrical underleaves associated with left-right symmetry in Mastigolejeunea, and the status of Mastigolejeunea undulata Gradst. & Grolle (Lejeuneaceae)

摘要

Underleaves of leafy liverworts may be bilaterally symmetrical or asymmetrical and are usually free from the leaves; occasionally they are adnate to the leaves on one or both sides. Adnate underleaves have been observed in the Lepodoziaceae genus Bazzania, in members of Lophocoleaceae (Chiloscyphus, Clasmatocolea, Heteroscyphus, Leptoscyphus, Lophocolea, etc.) and in the Lejeuneaceae genus Thysananthus (e.g., Fulford, 1963, 1976; Engel, 1980; Piippo, 1985; Srivastava & Srivastava, 2002; Sukkharak & Gradstein, 2010a; Sukkharak, 2014). Interestingly, adnation of underleaves in Thysananthus occurs in a left-right symmetrical pattern: on right-hand branches underleaves are connected to leaves on the left-hand side whereas on left-hand branches on the right-hand side (Sukkharak & Gradstein, 2010a). Left-right symmetry has to our knowledge not been observed in other genera with adnate underleaves and seems to support the distant relationship of Jungermanniales and Porellales (e.g., Frey & Stech, 2005; Heinrichs et al., 2005; He-Nygrén et al., 2006; Crandall-Stotler et al., 2009).