Research in Old World Gesneriaceae
Members of the mainly tropical family Gesneriaceae (African Violet family) are mostly herbs and subshrubs found in both the Old and New Worlds. The family is of great biogeographical interest: of the four subfamilies recognised in Weber's recent classification of the family in Kubitzki (Weber, 2004)*, Gesnerioideae is Neotropical, Coronantheroideae has a southern hemisphere distribution, and Epithematoideae and Didymocarpoideae (formerly Cyrtandroideae excluding Epithemateae) are Old World but with one species of the latter in Central America. Most species are plants of primary forests and so are under threat from human activity. At RBGE we are studying mainly the Epithematoideae and Didymocarpoideae, which encompasses 85 genera and over 1900 species.
*Weber, A. 2004. Gesneriaceae. In K. Kubitzki and J. W. Kadereit [eds.], The Families and Genera of Vascular Plants, Vol. 7: 63-158. Springer Verlag, Berlin.
The Royal Botanic Garden has had a long standing commitment to taxonomic work on the Old World Gesneriaceae. Recent monographic treatments have included Agalmyla, Didymocarpus, Ridleyandra and Didissandra. New genera such as Kaisupeea have also been published. Current taxonomic research is concentrated in Aeschynanthus and Cyrtandra. Fieldwork is an integral part of this, providing the raw material for these taxonomic studies and for the production of molecular phylogenies. Much of eastern Malesia and Indo-China is still botanically under-explored, and work is continuing in these areas. As the Gesneriaceae have been a focus of taxonomic research at the RBGE for many years, the herbarium, living collections and the library are particularly rich in materials for this work.
The genus Aeschynanthus is being revised. There are approximately 160 species in the genus which is distributed from the Himalayas and southern India east to southern China, and throughout Southeast Asia and Malesia to the Solomon Islands. Studies of Aeschynanthus seed morphology revealed a major division within the genus that correlates well with molecular results and distribution patterns. Monographic work will result in a series of regional revisions. More than half of the species of the genus are already in cultivation at the RBGE.
The genus Cyrtandra contains over 600 species and yet is poorly known. It is distributed through Southeast Asia out into the Pacific as far as Hawaii. The Sulawesi, Sumatran and Peninsular Malaysian Cyrtandra have recently been or are currently being revised, as are a group from Borneo, one of the centres of development for the genus. Cyrtandra presents a problem associated with many very large genera: how to revise them in an effective and timely fashion. Different approaches have been published in Cyrtandra including revising all of the species on a local level or on a regional level, and by identifying smaller and more manageable monophyletic groups and revising the species within those groups.
Atkins, H. & Cronk, Q.C.B. (2001). The genus Cyrtandra (Gesneriaceae) in Palawan, Philippines. Edinburgh Journal of Botany 58(3): 443-458.
Bramley, G.L.C. & Cronk Q.C.B. (2003) The Cyrtandra (Gesneriaceae) species of Mount Kerinci, Sumatra. Harvard Papers in Botany 7: 407-421.
Burtt, B.L. & Wiehler, H. (1995). Classification of the family Gesneriaceae. Gesneriana 1(1): 1-4.
Hilliard, O.M. & Burtt, B.L. (2002a). The genus Agalmyla. (Gesneriaceae - Cyrtandroideae). Edinburgh Journal of Botany 59(1): 1-210.
Mendum, M. (1998). Notes on Aeschynanthus (Gesneriaceae) from Seram. Edinburgh Journal of Botany 55: 359-365.
Middleton, D.J. (2007). A new species and a new combination in Aeschynanthus (Gesneriaceae) from Laos. Edinburgh Journal of Botany 64: 45-50.
Middleton, D.J. (2007). A revision of Aeschynanthus (Gesneriaceae) in Thailand. Edinburgh Journal of Botany 64: 363-429.
Middleton, D.J. & Scott, S.M. (2008). A new species of Agalmyla (Gesneriaceae) from Sulawesi. Edinburgh Journal of Botany 65: 49-52
Xu, Z.R., Burtt, B. L., Skog, L.E. & Middleton, D.J. (2008). A Revision Of Paraboea (Gesneriaceae). Edinburgh Journal of Botany 65: 161-347
In recent years the application of molecular techniques has allowed the accumulation of gene sequence data at a rapid rate. Molecular data have been applied extensively to investigations of phylogenetic relationships at different taxonomic levels in Gesneriaceae. The genera Aeschynanthus, Agalmyla, Cyrtandra, Didymocarpus and Streptocarpus have been investigated at the species level and, in collaboration with the University of Vienna, we are currently examining phylogenetic relationships at the generic level, particularly within the Old World subfamilies.
An excellent example for ‘phylogeny and classification' is the confusion around the placement of the genus Titanotrichum. In Kubitzki's* recent taxonomic classification of vascular plants it is treated under Scrophulariaceae: The genus was originally described under Scrophulariaceae but was later repeatedly regarded to belong to Gesneriaceae, and placed it in the latter family as a tribe of its own (Titanotricheae). Molecular studies carried out by Chun-Neng [Bruce] Wang (Wang et al. 2004) have confirmed that Titanotrichum is part of the family Gesneriaceae, and closely related to the New World subfamilies Coronantheroideae and Gesnerioideae.
* Kubitzki, K. & Kadereit, J. W. (2004). The Families and Genera of Vascular Plants, Vol. 7. Springer Verlag, Berlin.
MÖLLER M, M Pfosser, CG Jang, V Mayer, A Clark, ML Hollingsworth, MHJ Barfuss, YZ Wang, M Kiehn, A Weber (2009). A preliminary phylogeny of the "Didymocarpoid Gesneriaceae" based on three molecular data sets: incongruence with available tribal classifications. American Journal of Botany 96(5):989-1010.
Denduangboripant, J., Mendum, M. & Cronk, Q.C.B. (2001). Evolution in Aeschynanthus (Gesneriaceae) inferred from ITS sequences. Plant Systematics and Evolution 228: 181-197.
Mayer, V., Möller, M., Perret, M. & Weber, A. (2003). Phylogenetic position and generic differentiation of Epithemateae (Gesneriaceae) inferred from cpDNA sequence data. American Journal of Botany 90(2): 319-327.
Wang C.-N., Möller, M. & Cronk, Q.C.B. (2004) Phylogenetic position of Titanotrichum oldhamii (Gesneriaceae) inferred from four different gene regions. Systematic Botany 29(2): 407-418.
Other research on Gesneriaceae at RBGE
We also carry out research into the ontogeny and cytology of Gesneriaceae, which make extensive use of the highly diverse Gesneriaceae living collection. See also the pages describing evo-devo research into the family.
For further information, please contact the Gesneriaceae Research Group members:
Michael Möller: Streptocarpus, Evo-Devo, cytology and general enquiries.
David Middleton: Aeschynanthus, taxonomy
Carmen Puglisi Boea
Frieda Christie: seed ontogeny, SEM, light microscopy
Steve Scott: horticulture
Olive M. Hilliard
B. L. Burtt