Systematics Section / ASPT
Ballard, H. E. , de Paula-Souza, Juliana , Feng, Min .
Dismantling the Polyphyletic Genus Hybanthus Jacq. (Violaceae).
The genus Hybanthus Jacq. has been distinguished from other Violaceae by its conspicuously enlarged bottom petal with saccate to short-spurred base. Revisionary studies have detected over 100 distinct species in this pantropical and subtropical (rarely temperate) genus. Molecular phylogenetic analyses of the family using rbcL and trnL-F spacer gene sequences, including Hybanthus species from around the world, reveal Hybanthus as highly polyphyletic. The search for phenotypic corroboration and circumscription of seven biogeographically coherent chloroplast clades has uncovered a suite of 12 morphological, anatomical and cytogenetic characteristics circumscribing and differentiating the clades. These include features of corolla architecture and symmetry, filament and gland morphology in the androecium, fruit and seed morphology, calcium oxalate crystal morphology and distribution in the leaves, and base chromosome number. Cursory surveys suggest further differences in the embryo, pollen and vessel elements. Well defined genera to be segregated from Hybanthus sensu lato consist of (1) Hybanthus s. str. in Mesoamerica and the Caribbean [6 spp.]; (2) Cubelium Raf. in eastern North America [1 sp.]; (3 and 4) two unnamed groups in Mesoamerica [2 spp. each]; (5) Pombalia Vand. in the southwestern US and Latin America [55 spp.]; (6) Pigea DC. in South Africa, southern Australia and New Caledonia [15 spp.]; and (7) an unnamed group in Africa, Indochina and Southeast Asia [15-25 spp.].
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1 - Ohio University, Dept. of Environmental & Plant Biology, and Molecular & Cellular Biology Program, 317 Porter Hall, Athens, Ohio, 45701, USA
2 - Universidade de São Paulo, Herbário ESA, Av. Pádua Dias 11, C.P. 09, 13418-900 Piracicaba, São Paulo, , Brazil
3 - Chinese Academy of Sciences, Institute of Botany, Cas, The Center Of Systematic And Evolutionary Botany, 20 Nanxincun, Xiangshan, Beijing, 100093, China
segregate genus circumscription
Presentation Type: Oral Paper
Location: Salon G - Austin Grand Ballroom/Hilton
Date: Wednesday, August 17th, 2005
Time: 9:00 AM