Number of Genera
The number of genera is around 150, and is thus much higher than usually given in textbooks and horticultural pages. In his generic revision of Gesneriaceae for Kubitzki’s “Families and genera of vascular plants”, the present author recognized 147 genera (Weber 2004). In the classification paper of Weber et al. (2013) 150 genera were recorded. Christenhuiz & Byng (2016) presented the number 152, and at the time of posting this page (2017), the genus count is again 147 (but – as compared to Weber 2004 – with many new or re-established genera and others sunk in synonymy). For several reasons, there is permanent fluctuation:
(1) There is still some discussion about the delimitation of some genera; for instance, the Australian genus Lenbrassia is sometimes kept separate, sometimes included in Fieldia; the two species of Depanthus should possibly be returned to Coronanthera; it is still unsettled whether Sepikea should be kept separate from Cyrtandra; it has been suggested to split the huge genus Columnea into 5 genera, but there is no general agreement on this.
(2) New taxonomic revisions almost always end up in establishing new genera, reviving old genera, or combining genera.
(3) Molecular-phylogenetic studies have changed – and continue to change – our understanding of species relationships and generic delimitations dramatically; in particular, deep revisions have occurred in the Chinese Gesneriaceae. Many traditional Chinese genera have been split, merged or newly defined. In the paper “You win some you lose some …” Möller et al. (2015) summarized the taxonomic changes that have occurred in the Chinese Gesneriaceae and documented the high fluctuation in the number of genera.
Number of Species
Estimation of species number is still more difficult than the indication of the number of genera. The numbers given in some textbooks, and in particular by H. Wiehler (1983) “over 3700”, seems to be a bit generous. J. K. Boggan from the Smithsonian Institution has scrupulously summed up all species accepted in 2004, and presented a number of 3220 species (see World Checklist of Gesneriaceae, details in the next page, Genera and Species in Detail). This is, however, just a snapshot. New species are continuously being described (in an almost inflationary manner from China) and with every new revision, the number changes as old names are sunk into synonymy and new names are established. Much of this uncertainty is due to a few poorly known large genera, e.g., Besleria, Aeschynanthus, and especially Cyrtandra. In the latter genus the range of species number is given as 400 to 800 (Atkins et al. 2013: 652-818). If the highest number is taken, the total species number indeed may reach or even surpass 3700. A realistic and easily remembered number is perhaps 3500.