Subfamilies of the Gesneriaceae

Much of the information on this page is from two articles (WGRC 01 and WGRC 02) published in 2013 about the classification of the gesneriad family.  Even though they aren't 100% consistent with each other, they represent the best information we have at the moment about the composition of the family.

This table shows the four subfamilies that have been either widely accepted or proposed recently.  In the most recent publications, however, the Coronantheroideae have been submerged in the Gesnerioideae, and the Epithemateae put back into the Didymocarpeae, restoring the traditional two subfamilies.

The genus Sanango is sister to all the rest of the gesneriad family.  Therefore, if it is included in the family, a new subfamily must be created just to house this one genus with one species.  The choice is mostly a matter of convenience, since the phylogenetic placement of Sanango has apparently been settled.  The alternative is to create a new family just for that one species.

Gesnerioideae

The Western Hemisphere gesneriads almost all belong to the Gesnerioideae.  They have symmetrical cotyledons, unlike the Didymocarpoideae.  Most of them are pollinated by hummingbirds, and others are pollinated by euglossine bees.  A special pigment type (3-deoxyanthocyanins) is found in most genera of this subfamily.  These pigments are bright red or yellow, and are associated with hummingbird pollination.

The gesneria tribe (genera Gesneria, Rhytidophyllum, Bellonia) is found mostly on the islands of the Caribbean.  The sinningia subtribe is found mostly in Brazil.  Other gesnerioid tribes are found in Mexico, Central America, and northern South America.

Underground storage organs, like scaly rhizomes and tubers, are found in a number of genera of the Gesnerioideae.

Recently, it has been proposed that the genus Titanotrichum, from Taiwan and eastern mainland China, is actually a member of the Gesnerioideae.

Didymocarpoideae

The largest subfamily of the Gesneriaceae is, except for one species, confined to the eastern hemisphere.  [But see below.] It has two centers of concentration: South Africa and Madagascar (Saintpaulia and Streptocarpus) and Southeast Asia (all other genera).

The Didymocarpoideae are characterized by the accrescent cotyledon.

This subfamily includes two of the youngest and fastest-growing genera of the family: Cyrtandra and Aeschynanthus.  Possession of berry fruit has allowed Cyrtandra to colonize the (geologically young) islands of the Pacific.  It may be that the hairy seeds of Aeschynanthus also contribute to its dispersal through the South Pacific (over a range not as large as that of Cyrtandra).  Many (most?) aeschynanthus are pollinated by birds, although not by hummingbirds, since hummingbirds are confined to the western hemisphere.

There is one character found in a number of widely separated genera of this subfamily.  Streptocarpus, Boea, Paraboea, and several others have long fruits which are spirally twisted.  This may be an innovation to facilitate seed dispersal.  When the fruit is ripe, it splits open and untwists, releasing the seeds gradually.  Since Streptocarpus is not closely related to the others which have this trait and widely separated from them geographically, this trait must have evolved separately in the two groups.

Coronantheroideae

The late Hans Wiehler split off the tribe Coronanthereae from the Gesnerioideae into a separate subfamily, the Coronantheroideae.  Since tribal members Sarmienta and Mitraria share a special pigment (3-deoxyanthocyanins) with the Gesnerioideae, the chemical evidence suggests that the Coronantheroideae might perhaps be an entity multiplied without necessity.

Coronantheroids are native to the Pacific coast of Chile (Sarmienta, Mitraria, Asteranthera) and islands of the South Pacific (Fieldia, Negria, Rhabdothamnus).

Epithemateae

In Mayer et al. (2003), it was proposed that the tribe Klugieae, comprising some species of unusual gesneriads, be removed from the Didymocarpoideae to its own subfamily.  The largest genus in the tribe is Monophyllaea, with perhaps 30 species.

The implication of the split (and the gist of the molecular data) is that the Epithemateae branched off from the old-world gesneriaceae before any further radiation of the latter into Primulina, Streptocarpus, Aeschynanthus, Cyrtandra, and so on.  Furthermore, the surviving members of the subfamily have evolved a long way since the split.  Thus this tribe is the relic of what was probably a much more wide-spread and numerous group.

Most recent classifications have kept the Epithemateae in the subfamily Didymocarpeae as a sister group to the rest of the subfamily.

Most species of the Epithemateae are found in southeast Asia.  One relic, Epithema tenue, is found in western Africa.  This tribe also includes one species, Rhynchoglossum azureum, found in Central America.  How it got there nobody knows, since it does not have a fruit designed for long-range dispersal.  Perhaps not coincidentally, Rhynchoglossum is sister to the rest of the Epithemateae.  Rhynchoglossum contains about 10 species, one of them (R. notonianum from southern India) close to R. azureum, suggesting that the latter is a relatively recent immigrant to the neotropics.