Systematics Research
The Gentian Research Network
The Gentian Research Network is a free, not-for-profit, web-based forum for worldwide research on the natural history and evolution of the flowering plant family Gentianaceae (gentians).
Evolution of Gentians and Gentian Relatives
The focus of my research (starting when I was an undergraduate student) is the historical evolution and biodiversity of angiosperms, especially plants from the order Gentianales and its families: Apocynaceae (dogbanes and milkweeds), Gelsemiaceae (Carolina jessamine), Gentianaceae (gentians), Loganiaceae (strychnine family), and to a lesser degree Rubiaceae (coffee and madder family). I investigate species diversity, evolution, and biogeography based on phylogenetic reconstructions using anatomical, morphological, and molecular data. Much of my recent work has focused on the classification and phylogeny of the families Gentianaceae and Loganiaceae, for which I have provided the most recent international family classifications.
The gentian family is also the focus of my research in the evolution of morphology and New World biogeography. To understand the evolution of the gentian family I look at a group of plants and track their ancestors. In addition I follow changes in their looks and attributes through their evolution tens of millions of years into the past. I ask questions such as: How old are these species? Where did they evolve? How did they get there? Which traits have they inherited from their ancestors? Why do they look like this? How did they come to look like this? How do their flowers and fruits develop? What are their proper names and how many species are exist? Are they endangered? How are they useful to humans? Why do some grow in the mountains and some grow in rainforests or savannas?
I study these questions using modern molecular (DNA) and traditional (morphological) techniques. This requires field work for collecting new plant material, visits to herbaria in many countries to study specimens collected during the last 300 years, and work in my laboratory with DNA sequencing, herbarium material, computers, and microscopes. We also use methodologies such as histological preparations, SEM, GIS, statistical methods (multivariate statistics, etc.), light microscopy, and phylogenetic analyses (parsimony, Bayesian, and maximum likelihood). As part of my research I developed the Spatial Evolutionary and Ecological Vicariance Analysis (SEEVA) method with collaborators.
Our systematic botany research focuses mainly on the evolution and biogeography of the flowering plant order Gentianales, which includes:
- The gentians (Gentianaceae)
- The strychnine family (Loganiaceae)
- The false or yellow jessamine family (Gelsemiaceae)
- Milkweeds and dogbanes (Apocynaceae, including Asclepiadaceae)
- The coffee and quinine family (Rubiaceae)
More Specifics on Our Lab’s Taxonomic Research in Gentianales
What are gentians?
The gentian family (Gentianaceae), commonly known gentians, includes: deep-blue flowered alpine gentians (Gentiana), the pink-flowered centaury (Centaurium) and marsh-pink (Sabatia), as well as the cut flowers and potted plants of lisianthus (Eustoma) and Persian violet (Exacum). I use phylogenetic data from gentians to understand the biogeography of plants from tropical areas, especially in Latin America (the Neotropics). The gentian family comprises ca. 87 genera and ca. 1650 species classified into six tribes. Gentians are distributed worldwide, but has the highest number of genera, and greatest morphological diversity, in the tropical areas of the world. My research includes phylogenetic, biogeographic, taxonomic, and floristic projects using data derived from molecular, morphological, and anatomical studies (e.g. flower anatomy and development, palynology, seed anatomy, and DNA sequencing).
Publications: Struwe & Albert, 2002
Classification and monograph of the gentian family
The book Gentianaceae – Systematics and Natural History (Struwe & Albert, 2002) includes chapters written by experts on the evolution, biogeography, morphological and molecular-based phylogenetic studies, phytochemistry and pharmacology, seed anatomy, and palynology of the gentian family. The book also includes a new family-level classification of the gentians written in collaboration with Victor Albert, Joachim Kadereit, Jens Klackenberg, the late Siwert Nilsson, Mike Thiv, and Bernhard von Hagen. This was the first classification of gentians since Ernst Gilg’s system (1895). It was also the first comprehensive treatment of the family since Grisebach’s (1839) gentian monograph, which was published in Latin.
The most recent worldwide family treatment will be published soon as part of the global Families and Genera of Vascular Plant series (in press).
Publications: Struwe & Pringle, in press; Struwe & Albert, 2002; Struwe et al., 2002
Neotropical biogeography: geology, speciation and geography in Latin America
Neotropical biogeography is one of my main interests, focusing primarily on the tepuis and lowland white-sand savannas (on nutrient-poor and ancient sediments, with vegetation known as Amazon caatinga) in the Amazon basin. The tepuis are flat-topped and sharp-cliffed mountains in the Guiana Highlands in eastern Venezuela, northern Brazil, and Guyana. I work to answer research questions such as: Are the montane species of the tepui summits derived from ancestral lineages present in lowland rainforests and white-sand savannas, or from montane areas, such as the Andes? Are species endemic to the nutrient poor and ancient lowland white-sand areas in the Amazonas the oldest, relictual remnants of isolated evolutionary branches of the gentian family tree? What are the biogeographic relationships between plants in the Andes, the Amazon Basin, the Caribbean, and the two ancient geological Shields in South America (the Brazilian Shield in the southeast and the Guiana Shield in the north)? The tribe Helieae and the genus Potalia are used as model organisms for these biogeographic studies.
Publications: Mansion & Struwe, 2004; Struwe, 1999, in press; Struwe & Albert, 2002; Struwe et al., 2002, 2006
Evolution in tribe Helieae (Gentianaceae)
The gentian tribe Helieae occur only in Latin America and include Calolisianthus, Chelonanthus, Irlbachia, Macrocarpaea, Symbolanthus, and Tachia, etc. This monophyletic group of ca. 200 species contains both woody and herbaceous species and displays large variation in habit, leaves, flowers, and fruits. Many species are narrow endemics and restricted to small areas or habitats such as the tepui summits and their associated slopes, rainforests, or white-sand savannas, Andean mountain ridges, islands in the Caribbean, or highland savannas or forests in southeastern Brazil. Molecular data from the ITS and 5S-NTS DNA regions is used to resolve phylogenetic relationships within this group and to analyze biogeographical patterns. In the Helieae, many different pollinators can be found, ranging from hummingbirds in Symbolanthus and Lagenanthus, bats in some Chelonanthus and Macrocarpaea, insects in several genera, and hawkmoth pollination in Aripuana and Macrocarpaea. I investigate the evolution of floral traits and pollination syndromes, and also characters such as secondary woodiness, hairy leaves, inflorescence position, and pollen aggregation into tetrads and polyads in this group of gentians. The traditionally difficult generic delimitations and species relationships in the group are resolved using cladistic methods and modern molecular techniques.
Publications: Gould & Struwe, 2004; Grant & Struwe, 2001, 2003; Grant et al., 2006; Struwe, 2003; Struwe & Albert, 1998, 2002; Struwe & Gould, 2004; Struwe et al., 1999, 2002, 2005
Saccifolium (Gentianaceae; formerly Saccifoliaceae)
The phylogenetic position of Saccifolium bandeirae, from the Sierra de la Neblina mountain on the Brazil-Venezuela border, had been uncertain since its discovery decades ago when it was described as the sole member of the family Saccifoliaceae. Saccifolium has now been shown to be a member of the most basal clade of the Gentianaceae, the new tribe Saccifolieae, together with e.g. Curtia and the saprophytic genus Voyriella.
Publications: Struwe & Albert, 2002; Struwe et al., 2002; Thiv et al., 1999
Evolution in Potalieae (Anthocleista, Fagraea, and Potalia; Gentianaceae)
The tribe Potalieae was also excluded from Loganiaceae, and is now placed in the Gentianaceae, a strongly supported position based on molecular, morphological, anatomical, and phytochemical data. Phylogenetic and biogeographic relationships between and within Potalia, African-Malagasy Anthocleista, and Asian-Australian-Pacific Fagraea (all in the Potalieae) are being investigated using morphological and molecular data. Potalia, and its closely related genera Anthocleista and Fagraea of Potalieae, are tropical woody genera with showy flowers and fleshy or leathery berries, whereas most gentians are smaller herbs or shrubs with dry capsular fruits. Potalia is restricted to the Neotropics, and seven species are now recognized, compared to the only one species recognized previously. Potalia is also the gentian that is most used pharmacologically by people in the New World. It is used against snake bites and other animal bites, poisonings, stomach aches, inflammations, fungal infections, fevers, and many other health problems.
Publications: Struwe & Albert, 1997, 2002, 2004; Struwe et al., 1998, 2002
Flower development in gentians
My research also extends to studying floral and fruit development in Gentianaceae. I investigate postgenital fusion of ovaries, development of berries vs. capsules, and anatomy and vascularization of flowers in the tribe Helieae and Potalieae. Another research project is early flower development of the supermerous flowers of Potalia and Anthocleista of tribe Potalieae. Their unique flowers have 8-16 corolla and stamen parts instead of the usual 4 or 5 lobes/stamens characteristic for most other gentians.
Publications: Struwe, 1999; Struwe & Albert, 2002; Struwe et al., 1997, 2002
Evolution in Loganiaceae
I have also been working on the systematics of the tropical and subtropical family Loganiaceae in its older, traditional and larger circumscription. Nowadays, several former Loganiaceae genera are placed in other families, for example: the butterfly bush (Buddleja) in Buddlejaceae (order Lamiales), Desfontainia in Desfontainiaceae, yellow jessamine (Gelsemium) in Gelsemiaceae (Gentianales), Sanango and Peltanthera in Gesneriaceae (Lamiales), and Retzia in Stilbaceae (Lamiales). Left in Loganiaceae proper are only 13 genera, namely Antonia, Bonyunia, Gardneria, Geniostoma, Labordia, Logania, Mitrasacme, Mitreola, Neuburgia, Norrisia, Spigelia, Strychnos, and Usteria. Graduate student Cynthia Frasier participates in this project.
Publications: Albert & Struwe, 2002; Molina & Struwe, 2004; Struwe & Albert, 1997; Struwe & Motley, in press; Struwe et al., 1994.
Gentian Molecular Systematics
Gentianales: trnL sequence matrix (Struwe et al. 1999; 2002)
Gentianales – matK (Struwe et al., 2002)
Gentianales – trnL intron and matK, combined (Struwe et al., 2002)
Symbolanthus and Wurdackanthus: 5S-NTS (Gould & Struwe, 2004)
1. Gentianales – trnL intron
Data: aligned trnL intron sequences from Gentianales; Apocynaceae (incl. Asclepiadaceae), Gelsemiaceae, Gentianaceae, Loganiaceae (incl. Geniostomaceae), Rubiaceae, Saccifoliaceae, and Strychnaceae (incl. Antoniaceae), and some outgroups outside Gentianales. For GENBANK accession numbers see Struwe et al. (2002). Gaps are indicated with “-“; “?” indicates missing data. First four letters of taxon name indicates genus, next four species name.
Matrix type: Parsimony jackknife format (Xac), text-only.
References: Struwe, L., J. Kadereit, J. Klackenberg, S. Nilsson, M. Thiv, K. B. von Hagen, and V. A. Albert. (2002) Systematics, character evolution, and biogeography of Gentianaceae, including a new tribal and subtribal classification. In: Struwe, L. & V. A. Albert, eds. Gentianaceae – Systematics and Natural History. Cambridge University Press, Cambridge. See also: Thiv, M., L. Struwe, V. A. Albert, & J. W. Kadereit. 1999. The phylogenetic relationships of Saccifolium bandeirae Maguire & Pires (Gentianaceae) reconsidered. Harvard Papers in Botany 4: 519-526.
Contact person: Dr. Lena Struwe, lena.struwe@rutgers.edu
Date posted on WWW: 1998
Data also posted at The New York Botanical Garden’s web site [Note: summary at this page does not reflect most recent research results!]
2. Gentianales – matK
Data: aligned matK sequences from Gentianales; Apocynaceae (incl. Asclepiadaceae), Gelsemiaceae, Gentianaceae, Loganiaceae (incl. Geniostomaceae), Rubiaceae, Saccifoliaceae, and Strychnaceae (incl. Antoniaceae), and some outgroups outside Gentianales. For GENBANK accession numbers see Struwe et al. (2002). Gaps are indicated with “-“; “?” indicates missing data. First four letters of taxon name indicates genus, next four species name.
Matrix type: Parsimony jackknife format (Xac), text-only.
Reference: Struwe, L., J. Kadereit, J. Klackenberg, S. Nilsson, M. Thiv, K. B. von Hagen, and V. A. Albert. (2002) Systematics, character evolution, and biogeography of Gentianaceae, including a new tribal and subtribal classification. In: Struwe, L. & V. A. Albert, eds. Gentianaceae – Systematics and Natural History. Cambridge University Press, Cambridge.
Contact person: Dr. Lena Struwe, lena.struwe@rutgers.edu
Date posted on WWW: 10/01/01
View the data file: (html) (txt) File size 76 KB
3. Gentianales – trnL intron and matK, combined
Data: aligned trnL intron and matK sequences from Gentianales; Apocynaceae (incl. Asclepiadaceae), Gelsemiaceae, Gentianaceae, Loganiaceae (incl. Geniostomaceae), Rubiaceae, Saccifoliaceae, and Strychnaceae (incl. Antoniaceae), and some outgroups outside Gentianales. For GENBANK accession numbers see Struwe et al. (2002). Gaps are indicated with “-“; “?” indicates missing data. First four letters of taxon name indicates genus, next four species name.
Matrix type: Parsimony jackknife format (Xac), text-only.
Reference: Struwe, L., J. Kadereit, J. Klackenberg, S. Nilsson, M. Thiv, K. B. von Hagen, and V. A. Albert. (2002) Systematics, character evolution, and biogeography of Gentianaceae, including a new tribal and subtribal classification. In: Struwe, L. & V. A. Albert, eds. Gentianaceae – Systematics and Natural History. Cambridge University Press, Cambridge.
Contact person: Dr. Lena Struwe, lena.struwe@rutgers.edu
Date posted on WWW: 10/01/01
View the data file: (html) (txt) File size 116 kb
4. Symbolanthus and Wurdackanthus (Helieae: Gentianaceae): 5S-NTS
Data: aligned 5S-non transcribed spacer (5S-NTS) sequences from Symbolanthus and Wurdackanthus, with Chelonanthus as outgroup. For GENBANK accession numbers, see Gould & Struwe (2004), and these are also listed after each taxon name in the matrix. Abbreviations before Genbank numbers are our DNA extraction names. Gaps are indicated with “-“; “?” indicates missing data.
Matrix type: NEXUS format (PAUP), text-only.
Reference: Gould, K. R. & L. Struwe. 2004. Phylogeny and evolution of Symbolanthus and Wurdackanthus (Gentianaceae-Helieae) in the Guayana Highlands and Andes, based on ribosomal 5S-NTS sequences. Ann. Missouri Bot. Gard. 91: 438-446.
Contact person: Dr. Lena Struwe, lena.struwe@rutgers.edu
Date posted on WWW: 09/15/02
View the data file: (html) (txt) File size 6 kb