Gesneria and Rhytidophyllum are sister groups (i.e., share a recent common ancestor), and as a result of their close relationship, they share many distinguishing features. The following list of characters (Fig. 2) differentiates them from all other members of the New World Gesneriaceae.
- The ovaries are inferior in Gesneria and Rhytidophyllum. Inferior means that the ovary is below the attachment of the petals and sepals (Fig. 2A). In contrast, most New World Gesneriaceae, with very few exceptions, have superior ovaries. Superior means that the ovary is above the attachment of the petals and sepals (Fig. 2B).
- The leaf arrangement in Gesneria and Rhytidophyllum is alternate (Fig. 2C). In contrast, most other New World Gesneriaceae are characterized by opposite leaves (Fig. 2D).
- The fruits in Gesneria and Rhytidophyllum have woody capsules (Fig. 2E). In contrast, most fruits of New World Gesneriaceae have fleshy berries or fleshy capsules (Fig. 2F), with few exceptions.
- The nectary for Gesneria and Rhytidophyllum is annular (Fig. 4G). In contrast, nectaries for most other New World genera are lobed. Examples include five separate lobes (esp. Columnea) to bilobed or single-lobed on the upper surface of the ovary.