Phylogenetics and Systematics
My research revolves around
generating molecular phylogenetic hypotheses at the species and higher level
mainly of Old World Gesneriaceae. We are particularly interested in the testing
of systematic treatments of the study groups, but also to unravel evolutionary
histories. We mainly use nuclear ribosomal and chloroplast DNA sequence data.
We also test the utilisation of putative single-copy developmental genes for
phylogenetic purposes, such as the flower developmental gene CYCLOIDEA,
for this purpose.
For some genera, such as Agalmyla, Didymocarpus and Streptocarpus we have constructed extensive phylogenies.
The recent focus was the unravelling of inter-generic relationships among OW Gesneriaceae, and testing the monophyly and relationships of traditionally accepted genera and tribes. This research has lead to the abandonment of these tribes and a new informal classification formulated in Weber (2004). It also resulted in the re-definition of several genera, such as Hemiboea, Oreocharis and Petrocodon, and the split into five genera, and the abandonment of the genus name, Chirita. This line of research is ongoing and currently focuses is the inter-generic and clade relationships of the Old World Gesneriaceae.
[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.]
* taxonomic revisions in Madagascan Streptocarpus (with Prof Dirk U Bellstedt, University of Stellenbosch).
* The genus Paraboea (Gesneriaceae): taxonomy, biogeography, phylogeny and evolution (with Carmen Puglisi, RBGE/University of Edinburgh; Richard Milne, University of Edinburgh; David Middleton RBGE).
* Conservation biology of Paraisometrum mileense W.T.Wang [now Oreocharis mileensis (W.T.Wang) Mich.Möller & A.Weber]. (with CHEN Wen-Hong, WANG Hong, SHUI Yu-Min, Kunming Institute of Botany).
* Tribal relationships in Old World Gesneriaceae (with Prof Anton Weber & Prof Michael Kiehn, University of Vienna, Austria; Dr Michelle Hollingsworth & Alexandra Clark, RBGE).
* Phylogenetic relationships of monotypic and small genera in Gesneriaceae from China (with Prof Wei Yi-Gang, Guangxi Institute of Botany).
Chen WH, M MÖLLER, MD Zhang, YM Shui (2012). Paraboea hekouensis and P. manhaoensis, two new species of Gesneriaceae from China. Annales Botanici Fennici 49:179-187.
MÖLLER M, A Forrest, YG Wei, A Weber (2011). A molecular phylogenetic assessment of the advanced Asiatic and Malesian didymocarpoid Gesneriaceae with focus on non-monophyletic and monotypic genera. Plant Systematics and Evolution 292(3-4):223-248.
MÖLLER M, D Middleton, K Nishii, YG Wei, S Sontag, A Weber (2011). A new delineation for Oreocharis incorporating an additional ten genera of Chinese Gesneriaceae. Phytotaxa 23:1-36.
Puglisi C, DJ Middleton, P Triboun, M MÖLLER (2011). New insights into the relationships between Paraboea, Trisepalum, and Phylloboea (Gesneriaceae) and their taxonomic consequences. Taxon, 60(6):1693-1702.
Puglisi C, YG Wei, K Nishii, M MÖLLER (2011). Oreocharis × heterandra (Gesneriaceae): a natural hybrid from the Shengtangshan Mountains, Guangxi, China. Phytotaxa 38:1-18.
Weber A, DJ Middleton, A Forrest, R Kiew, CL Lim, AR Rafidah, TL Yao, M MÖLLER (2011). Molecular systematics and remodelling of Chirita and associated genera (Gesneriaceae). Taxon 60:767-790.
Weber A, YG WEI, C Puglisi, F Wen, V Mayer, M MÖLLER (2011). A new definition of the genus Petrocodon (Gesneriaceae). Phytotaxa 23:49-67.
Weber A, YG Wei, S Sontag, M MÖLLER (2011). Inclusion of Metabriggsia into Hemiboea (Gesneriaceae). Phytotaxa 23:37-48.
Middleton DJ, C Puglisi, P Triboun, M MÖLLER (2010). Proposal to conserve Paraboea against Phylloboea and Trisepalum (Gesneriaceae). Taxon 59:1603.
Wei YG, F Wen, WH Chen, YM Shui, M MÖLLER (2010). Litostigma, a new genus from China: a morphological link between basal and derived Didymocarpoid Gesneriaceae. Edinburgh Journal of Botany 67(1):161-184.
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.
Palee P, J Denduangboripant, V. Anusarnsunthorn, M MÖLLER (2006). Molecular phylogeny and character evolution of Didymocarpus (Gesneriaceae) in Thailand. Edinburgh Journal of Botany 63(2&3):231-251.
MacMaster G, M MÖLLER, M Hughes, TJ Edwards, DU Bellstedt. (2005) A new species of Streptocarpus (Gesneriaceae) endemic to Madagascar. Adansonia 27(1):131-136.
Wang CN, M MÖLLER, QCB Cronk (2004). Phylogenetic position of Titanotrichum oldhamii (Gesneriaceae) inferred from four different gene regions. Systematic Botany 29(2):407-418.
Mayer V, M MÖLLER, M Perret, A Weber, A. (2003). Phylogenetic position and generic differentiation of Epithemateae (Gesneriaceae) inferred from cpDNA sequence data. American Journal of Botany 90(2):319-327.
MÖLLER M, QCB Cronk (1999). New approaches to the taxonomy of Saintpaulia and Streptocarpus. In: S Andrews, AC Leslie, C Alexander (eds.) Taxonomy of Cultivated Plants. Proceedings of the Third International Symposium, pp. 253-264 Royal Botanic Gardens, Kew.
Smith JF, ME Kresge, M MÖLLER, QCB Cronk (1998). A cladistic analysis of ndhF sequences from representative species of Saintpaulia and Streptocarpus sections Streptocarpus and Streptocarpella (Gesneriaceae). Edinburgh Journal of Botany 55(1):1-11.
MÖLLER M, QCB Cronk (1997a). Origin and relationships of Saintpaulia (Gesneriaceae) based on ribosomal DNA internal transcribed spacer (ITS) sequences. American Journal of Botany 84(8):956-965.
MÖLLER M, QCB Cronk (1997b). Phylogeny and disjunct distribution: evolution of Saintpaulia (Gesneriaceae). Proceedings of the Royal Society of London, Series B 264:1827-1836.
Character Evolution and Evolutionary Development
Robust phylogenetic hypotheses are
essential for an analysis of morphological changes over evolutionary times. In
Evo-Devo we are utilizing these phylogenetic trees to investigate the type and
direction of morphological change and the level of parallelism, convergence, in
character evolution. For instance, actinomorphic flowers are rare in OW
Gesneriaceae, and only 5 out of ~85 genera possess regular flowers. Our results
have shown that this trait has evolved independently several times.
We are also interested in understanding the underlying genetics of inter-specific phenotype variation. To this end we isolate candidate genes putatively responsible for the morphological variation and study their expression pattern.
We have shown that the gene CYCLOIDEA (CYC), involved in flower symmetry is likely down-regulated rather than switched off in actinomorphic genera.
Besides floral characters we study the evolution of vegetative variation. The African genus Streptocarpus shows a very labile vegetative morphology, with unifoliate, rosulate and caulescent morphs. We study genes, shown to be involved in meristem establishment and maintenance in the model plant Arabidopsis, for their behaviour in Streptocarpus. We investigated genes such as FILAMENT (FIL), PHANTASTICA (PHAN), WUSCHEL (WUS), and KNOX1 genes, such as BREVIPEDICELLUS (BP) and SHOOTMERISTEMLESS (STM), for their involvement in the meristem formation in Streptocarpus from embryo development to mature plants.
* Meristem evolution in Gesneriaceae (with Dr Kanae Nishii, Prof Wang Chun-Neng [Bruce], National Taiwan University, Taipei).
* Hormone involvement in anisocotyly of Streptocarpus (with Dr Kanae Nishii, Prof Wang Chun-Neng [Bruce], National Taiwan University, Taipei; Dr Alberto Spada, University of Milan).
* The involvement and expression of meristem genes in the phyllomorphic concept in Streptocarpus (Gesneriaceae) (with Prof Toshiyuki Nagata, University of Tokyo; Dr Alberto Spada, University of Milan).
* Genetics and evolution of floral shapes in Streptocarpus (Gesneriaceae) (with Prof Wang Chun-Neng [Bruce], National Taiwan University, Taipei)
Nishii K, T Nagata, CN Wang, M MÖLLER (2012). Light as environmental regulator for germination and macrocotyledon development in Streptocarpus rexii (Gesneriaceae). South African Journal of Botany 81:50-60.
Nishii, K, CN Wang, A Spada, T Nagata, M MÖLLER (2012). Gibberellin as a suppressor of lateral dominance and inducer of apical growth in the unifoliate Streptocarpus wendlandii. New Zealand Journal of Botany doi: 10.1080/0028825X.2012.671775.
Nishii K, M MÖLLER, T Nagata (2011). One-leaf plants and their relatives. Japanese Journal of Heredity, 65:10-17.
Nishii K, M MÖLLER, C Kidner, A Spada, R Mantegazza, CN Wang, T Nagata (2010). A complex case of simple leaves: indeterminate leaves co-express ARP and KNOX1 genes. Developmental Genes and Evolution 220:25-40.
Tononi P, M MÖLLER, S Bencivenga, A Spada (2010). GRAMINIFOLIA homolog expression in Streptocarpus rexii is associated with the basal meristems in phyllomorphs, a morphological novelty in Gesneriaceae. Evolution & Development 12(1):61-73.
Mantegazza R, P Tononi, M MÖLLER, A Spada (2009). WUS and STM homologues are linked to the expression of lateral dominance in the acaulescent Streptocarpus rexii (Gesneriaceae). Planta 230(3): 529-542.
Mantegazza R, M MÖLLER, CJ Harrison, S Fior, C DeLuca, A Spada. (2007). Anisocotyly and meristem initiation in an unorthodox plant, Streptocarpus rexii (Gesneriaceae). Planta 225(3):653-663.
Palee P, J Denduangboripant, V. Anusarnsunthorn, M MÖLLER (2006). Molecular phylogeny and character evolution of Didymocarpus (Gesneriaceae) in Thailand. Edinburgh Journal of Botany 63(2&3):231-251.
Harrison J, M MÖLLER, J Langdale, Q Cronk, A Hudson (2005). The role of KNOX genes in the evolution of morphological novelty in Streptocarpus. The Plant Cell 17:430-443.
Wang CN, M MÖLLER, QCB Cronk (2004a). Altered expression of GFLO, the Gesneriaceae homologue of FLORICAULA/LEAFY, is associated with the transition to bulbil formation in Titanotrichum oldhamii. Development Genes and Evolution 214:122-127.
Wang CN, M MÖLLER, QCB Cronk (2004b). Aspects of sexual failure in the reproductive processes of a rare bulbiliferous plant, Titanotrichum oldhamii (Gesneriaceae) in subtropical Asia. Sexual Plant Reproduction 17:23-31.
Wang YZ, M MÖLLER, DY Hong (2002). Floral development in Whytockia (Gesneriaceae) with phylogenetic implications. Plant Biology 4:492-502.
MÖLLER M, QCB Cronk (2001a). Evolution of morphological novelty: a phylogenetic analysis of growth patterns in Streptocarpus (Gesneriaceae). Evolution 55(5):918-929.
Citerne HL, M MÖLLER, QCB Cronk (2000). Diversity of cycloidea-like genes in Gesneriaceae in relation to floral symmetry. Annals of Botany 86(1):167-176.
Harrison CJ, M MÖLLER, QCB Cronk (1999). Evolution and development of floral diversity in Streptocarpus and Saintpaulia. Annals of Botany 84:49-60.
MÖLLER M, M Clokie, P Cubas, QCB Cronk (1999). Integrating molecular phylogenies and developmental genetics: a Gesneriaceae case study. In: PM Hollingsworth, RM Bateman, RJ Gornall (eds) Molecular systematics and plant evolution. 375-402. London: Taylor & Francis.
Cronk QCB, M MÖLLER (1997a). Genetics of floral symmetry revealed. Trends in Ecology and Evolution 12(3):85-86.
Cronk QCB, M MÖLLER (1997b). Strange morphogenesis - organ determination in Monophyllaea. Trends in Plant Science 2(9):327-328.
Finescale Biogeography and Speciation
My interest in biogeography in Gesneriaceae is the effect of biogeographic history on speciation. This research focuses on fine-scale mechanisms of plant dispersal and speciation. While continental drift has affected plant communities on a large scale over a larger period of geological time, fluctuations in global climate in recent times (in the late Tertiary and Quarternary) affected greatly regional floras. This is shown as an example for the genus Streptocarpus on the African continent, where the species evolved in a North (Kenya/Tanzania) to South (South Africa) cline. Under a Leverhulme funded project, collaborators from the University of Stellenbosch and Natal, we investigated this North-South trend in detail at the population level and found strong evidence that suggests a link between species range expansion, and Pleistocene climatic cycles, the populations utilising coastal forest micro-refugia as stepping stones.
Recent biogrographic work focused on China and widespread the genus Corallodiscus, occurring from the Western Ghat in India to Hebei province in northeastern China.
* fine-scale biogeography in Corallodiscus (Gesneriaceae) in China (with Prof LI DeZhu, Dr GAO Lian-Ming, Kunming Institute of Botany, Yunnan, China).
* hybridization and incomplete lineage sorting in African Streptocarpus (with Prof Dirk U Bellstedt, University of Stellenbosch; Mark Hughes, RBGE).
* Biosystematic studies in the genus Corallodiscus (Gesneriaceae) in China and adjacent regions (with Dr LI Jie, Xishuangbanna Tropical Botanical Garden, Yunnan, China).
* Biogeography and speciation in the genus Streptocarpus (Gesneriaceae) (with Dr Mark Hughes, RBGE, Prof Dirk U Bellstedt, University of Stellenbosch & Prof Trevor J Edwards, University of Natal).
Gao LM, ZR Zhang, P Zhou, M MÖLLER, DZ Li (2012). Microsatellite makers developed for Corallodiscus lanuginosus (Gesneriaceae) using the FIASCO approach. American Journal of Botany, Primer Notes & Protocols in Plant Sciences, in press.
Kokubugata G, Y Hirayama, CI Peng, M Yokota, M MÖLLER (2011). Phytogeographic aspects of Lysionotus pauciflorus sensu lato (Gesneriaceae) in the China, Japan and Taiwan regions: phylogenetic and morphological relationships and taxonomic consequences. Plant Systematics and Evolution 292(3-4):177-188.
Hughes M, M MÖLLER, TJ Edwards, DU Bellstedt, M De Villiers (2007). The impact of pollination syndrome and habitat on gene flow: a comparative study of two Streptocarpus (Gesneriaceae) species. American Journal of Botany 94(10).
Hughes M, G MacMaster, M MÖLLER, DU Bellstedt, TJ Edwards (2006). Breeding system of a plesiomorphic floral type: an investigation of small flowered Streptocarpus (Gesneriaceae) species. Plant Systematics and Evolution 262:13-24.
Hughes M, M MÖLLER, DU Bellstedt, TJ Edwards, M De Villiers (2005). Refugia, dispersal and divergence in a forest archipelago: a study of Streptocarpus in eastern South Africa. Molecular Ecology 14:4415-4426.
Hughes M, M MÖLLER, DU Bellstedt, TJ Edwards, M Woodhead (2004). EST and random genomic nuclear microsatellite markers for Streptocarpus. Molecular Ecology Notes 4:36-38.
MÖLLER M, KJ Brooks, M Hughes (2004). Plastid inheritance in Streptocarpus (Gesneriaceae) and an inferred hybrid origin for a population of S. aff. primulifolius from Igoda River, South Africa. Edinburgh Journal of Botany 60(3):389-408.
Wang CN, M MÖLLER, QCB Cronk (2004). Population genetic structure of Titanotrichum oldhamii (Gesneriaceae), a subtropical bulbiliferous plant with mixed sexual and asexual reproduction. Annals of Botany 93:201-209.
Pico FX, M MÖLLER, NJ Ouborg, QCB Cronk (2002). Single nucleotide polymorphisms in the coding region of the developmental gene Gcyc in natural populations of the relict Ramonda myconi (Gesneriaceae). Plant Biology 4:625-629.
MÖLLER M, QCB Cronk (2001). Phylogenetic studies in Streptocarpus (Gesneriaceae): reconstruction of biogeographic history and distribution patterns. Systematics and Geography of Plants 71(2):545-555.
Genome and Chromosome Evolution
In cytology, the chromosome and
genome evolution, as studied in the context of molecular phylogenetic
hypotheses, is of particular interest to me and my collaborators. Our main
focus in the family Gesneriaceae, is on genera where robust molecular
phylogenies exist, such as Aeschynanthus, Agalmyla, Streptocarpus.
Here we are interested in understanding the evolution of basic chromosome
numbers, as suggested by the phylogenetic trees. Great variations can be found
in the patterns of changes of basic numbers between related genera; while Streptocarpus
is rather conservative showing only one change in basic number, the genus Aeschynanthus
displays several parallel changes in the basic chromosome number.
Ribosomal DNA are arranged in hundreds of copies in tandem arrays in at least one nucleolar organiser region (NOR) per haploid genome per cell. We founds that in Streptocarpus at least, these NOR sites are inherited as a single unit (or locus) rather than as mosaic sequences of both parents as found in some other plants, such as Amelanchier or Ilex. This has important implications on the interpretation of phylogenetic trees where hybridisation is involved.
We also study chromosomal markers, such as the ribosomal DNA sites, the data source for numerous phylogentic analyses, for which fluorescent probes exist. Fluorescent in situ hybridisation (FISH) is particularly helpful in cases where no variation in chromosome numbers exist between species. We analysed selected genera of Gesneriaceae for their variation in these markers using FISH. Our initial results show that different, genus specific patterns exist in Gesneriaceae.
Over recent years, our living research collection has increased dramatically, allowing cytotaxonomic studies to proceed. Currently, we determine the basic chromosome numbers of taxa not previously examined focusing on newly defined genera, based on our molecular phylogenetic work.
With input from M. Kiehn (University of Vienna), L. Skog (Smithsonian Institution, Washington) and M. Pullan (RBGE) we have prepared a webbrowser-based database for cytological investigations on Gesneriaceae, ‘ WebCyte'. This research tool allows easy access to all current cytological data published for the family.
* Chromosome numbers among the newly defined genera in Old World Gesneriaceae (with Frieda Christie, Sadie Barber, RBGE).
* Evolution of rDNA in selected genera of Old World Gesneriaceae (with Dr Goro Kokubugata, Tsukuba Botanical Garden, Japan; Dr Kwiton Jong, RBGE).
Christie F, S Barber, M MÖLLER (2012). New chromosome counts in Old World Gesneriaceae: numbers for species hitherto regarded as Chirita, and their systematic and evolutionary significance. Edinburgh Journal of Botany 69(2):323-345.
MÖLLER M, G Kokubugata, K Jong (2008). Aspects of genome evolution in Gesneriaceae: patterns of 45S-nrDNA site evolution based on evidence from fluorescent in-situ hybridization (FISH). International Journal of Plant Sciences 169(5): 667-676.
Denduangboripant J, QCB Cronk, G Kokubugata, M MÖLLER (2007). Variation and inheritance of nuclear ribosomal DNA clusters in Streptocarpus (Gesneriaceae) and their biological and phylogenetic implications. International Journal of Plant Sciences 168(4):455-467.
Jong K, M MÖLLER (2000). New chromosome counts in Streptocarpus (Gesneriaceae) from Madagascar and the Comoro Islands and their taxonomic significance. Plant Systematics and Evolution 224:173-182.
MÖLLER M, M Kiehn (2004). A synopsis of cytological studies in Gesneriaceae. Edinburgh Journal of Botany 60(3):425-447.
Zhou P, ZJ Gu, M MÖLLER (2004). New chromosome counts and nuclear characteristics for some members of Gesneriaceae subfamily Cyrtandroideae from China and Vietnam. Edinburgh Journal of Botany 60(3):449-466.
Molecular - morphological approaches to a complex group
* Population genetics, phylogenetics and taxonomic revision of the genus Taxus L. (Taxaceae) in China (with Prof Li De-Zhu, Dr Gao Lian-Ming, Kunming Institute of Botany, China; Prof Mary Gibby, Dr Michelle Hollingsworth, Dr Robert Mill, RBGE).
Taxus plants are an important source for taxol, an effective anti-tumor agent for cancer treatments. Natural resources are depleted rapidly over the last decades and the plants have become endangered and populations fragmented. This collaborative projects investigates the genetic status of Taxus wallichiana in China and adjacent regions with the ultimate goal to clarify its taxonomy in this area.
Liu J, LM Gao, DZ Li, DQ Zhang, M MÖLLER (2011). Cross-species amplification and development of new microsatellite loci for Taxus wallichiana (Taxaceae). American Journal of Botany, Primer Notes & Protocols in Plant Sciences 98(4): e70-73.
Liu J, M MÖLLER, LM Gao, DQ Zhang, DZ Li (2011). DNA barcoding for the discrimination of Eurasian yews (Taxus L., Taxaceae) and the discovery of cryptic species. Molecular Ecology Resources 11:89-100.
Zhang XM, LM Gao, M MÖLLER, DZ Li (2009). Molecular evidence for fragmentation among populations of Taxus wallichiana var. mairei, a highly endangered conifer in China. Canadian Journal of Forest Research 39(4):755-764.
Gao LM, M MÖLLER, XM Zhang, ML Hollingsworth, J Liu, RR Mill, M Gibby, DZ Li (2007). High variation and strong phylogeographic pattern among cpDNA haplotypes in Taxus wallichiana (Taxaceae) in China and North Vietnam. Molecular Ecology doi:10.1111/j.1365-294X.2007.03537.x
MÖLLER M, LM Gao, RR Mill, DZ Li, ML Hollingsworth, M Gibby (2007) Morphometric analysis of the Taxus wallichiana complex (Taxaceae) based on herbarium material. Botanical Journal of the Linnean Society 155(3):307-335.
Shah A, DZ Li, LM Gao, HT Li, M MÖLLER (2007). Genetic diversity within and among populations of the endangered species Taxus fuana (Taxaceae) from Pakistan and implications for its conservation. Biochemical Systematics and Ecology in press.
Shah A, DZ Li, M MÖLLER, LM Gao, ML Hollingsworth, M Gibby (2007). Delimitation of Taxus fuana Nan Li & R.R. Mill (Taxaceae) based on morphological and molecular data. Taxon in press.
* Taxonomic revision of the genus Vitex L. (Lamiaceae) in Africa (with Prof Fatima Sales, Celia Cabral, University of Coimbra, Portugal). (Other people involved: Dr D. Harris, RBGE, R. Olmstead, University of Washington, US)
The genus Vitex is investigated at species level and phylogenies are generated using samples collected to reflect its panglobal range of distribution. Reconstruction of the geographic history of the genus attempts to reveal the origin of the genus, and the direction and means of range expansion. More detailed studies have been carried out on the morphology, including pollen, and essential oils of African taxa belonging to Grex Pilosae of Pieper.
Cabral C, M MÖLLER, F Sales (2008). The palynological compass: a case study in Viticoideae (Vitex L.). Microscopy and Microanalysis 14 (supp 3):158-161.
Refuting Gondwanaland Origins
* Biogeography of the genus Exacum and tribe Exaceae (with Dr Yuan Yong-Ming, Université de Neuchâtel, Switzerland)
The genus Exacum (Gentianaceae) has a classical Gondwanaland distribution, and its origin and diversification has been linked to this break-up of this paleo-continent more than 100 MY ago. In this collaboration project we use fossils and molecular dating methods to demonstrate that the genus is much too young to have originated on the Gonwanan continent, and that its present day distribution is more likely to have resulted from an origin in Madagascar not before the Eocene followed by long-distance dispersals to Sri Lanka and southern India through the Indian-Ocean-Basin (IOB).
Yuan YM, S Wohlhauser, M MÖLLER, J Klackenberg, M Callmander, P Küpfer (2005). Phylogeny and biogeography of Exacum (Gentianaceae): a disjunctive distribution in the Indian Ocean Basin resulted from long distance dispersal and extensive radiation. Systematic Biology 54(1):21-34.
Yuan YM, S Wohlhauser, M MÖLLER, P Chassot, G Mansion, J Grant, P Küpfer, J Klackenberg (2003). Monophyly and relationships of the tribe Exaceae (Gentianaceae) inferred from nuclear ribosomal and chloroplast DNA sequences. Molecular Phylogenetics and Evolution. 28(3):500-517.