The increased application of phylogenetic hypotheses for a spectrum of biological questions requires that these phylogenetic trees are not only well resolved but also well supported statistically. Results from basal angiosperms and selected eudicot orders indicate that non-coding DNA (spacers and introns) are highly efficient markers for phylogenetic reconstruction within angiosperms. Up to now, spacers and introns had largely been employed at the genus and family levels.
The eudicot clade comprises 75% of angiosperm species diversity. Relationships among several major lineages are still insufficiently known, as are phylogenies for several clades such as Ranunculales, Lamiales and Malpighiales. The project focuses on the mutational dynamics of non-coding genomic regions and their phylogenetic potential for further resolving the tree of eudicots. It is assumed that structure and selective constrains are lower in group I-introns and spacers as compared to group II-introns, whereas the quality of phylogenetic signal is higher. Structure and function of a genomic region will therefore govern levels of homoplasy. Because complex secondary structure models of introns are available or predictable via minimum energy calculations we are studying structural effects of mutations. Expected outputs of the project are threefold: (1) Understanding eudicot evolution, (2) Explaining different qualities of phylogenetic signals (=levels of homoplasy) and therefore differences in the performance of genomic regions in phylogeny reconstruction, and (3) Problem oriented optimization of specific molecular marker application or combination.
Anna-Magdalena Barniske: Molecular Evolution and Phylogenetic Signal of Chloroplast Introns (PhD)
Andreas Worberg: Phylogeny and Evolution of Rosids (PhD)
Karsten Salomo: Molecular Evolution of the petD group II Intron in Asterids (Diploma)
Nadja Korotkova: Phylogeny of Malpighiales (eudicots): Analysis of a Radiation with petD group II-Intron Sequences (Diploma completed June 2006)
Molecular Evolution of Chloroplast Introns and their Phylogenetic Signal
The chloroplast genome contains a variety of group II introns but only a single group I intron in trnL. Although secondary structures of group I and group II introns are strikingly different, they can be characterized by a patchwork pattern consisting of highly conserved elements that alter with more freely evolving regions. In this project the mutational dynamics of the different intron partitions is analysed (e.g., the PQRS catalytic core in group I introns versus P8; or the conserved helical parts of domains I to VI in group II introns versus the remaining stem-loop regions). By comparing similar structural elements from a number of introns the structural effects on sequence variability and their impact on the phylogenetic signal are studied. A wide spectrum of intron sequences from different genomic locations across eudicots offers the possibility to detect lineage specific effects and possible effect of a non-independent evolution of intron groups.
Anna-Magdalena Barniske (PhD)
Andreas Wilm (Universität Düsseldorf)
Evolution of Growth Forms within Ranunculales
In many angiosperm families and genera a shift from one growth form to another can be observed. While changes from a primary woody to herbaceous plants seems to be a regular case, the opposite way is comparatively rare. For Aristolochiaceae we were able to show that self-supporting species from Central America (Aristolochia arborea, A. tricaudata, A. salvadorensis) derived from lianescent or herbarceous ancestors by preserving an early developmental stage of juvenile lianas.
Currently we are interested in the shift of growth forms in the primarily lianescent family Lardizabalaceae, and within the genus Clematis. By combining anatomical, biomechanical data with molecular phylogenies we hope to explain the origin of indivicual species that are shrubs or small trees (e.g. Decaisnea in Lardizabalaceae). Furthermore we would like to find out whether the self-supporting growth in Clematis occurred only once or has a multiple origin e.g. Clematis heracleifolia, C. urticifolia.
N.N. (see above)
Prof. Dr. Nick Rowe (University of Montpellier)
The rosid clade comprises a large variety of plants (about 70.000 species and >140 families) and accounts for ~30% of angiosperm species diversity. Within the rosids 14 monophyletic orders have been established (see APG II, 2003) and it is also likely that Crossosomatales, Geraniales, and Myrtales are first branching, wheres the remaining orders fall into two big clades, known as eurosids I and II. Relationships among many of these orders and also among many families (most strikingly within Malpighiales) still remain to be elucidated. In this project a number of non-coding and rapidly evolving genomic regions is sequenced for about 140 genera representing most families. Phylogenetic analyses and work on molecular evolutionary patterns are intended to evaluate the contribution of chloroplast introns and spacer data to understanding the evolution of rosids.
Andreas Worberg (PhD)
Radiation of Malpighiales
The Malpighiales are the most speciose clade in the rosids. Current efforts aim to better understand the molecular evolution of a number of fast-evolving and non-coding genomic regions in Malpighiales and to evaluate their phylogenetic utility. It is hoped to improve resolution within the order using a set of introns and spacers.
Nadja Korotkova (diploma completed June 2006)
Pollen characters provide highly significant information at various taxonomic levels in angiosperms. Work aims at understanding pollen evolution in a phylogenetic context and to search for synapomorphies for clades found with molecular data. The Caryophyllales and in particular the Amaranthaceae-Chenopodiaceae alliance are used as a model because of a relatively large amount of pollen data available and phylogenetic relationships becoming essentially clear.
Ivonne Sanchez-del Pino: Phylogeny and floral evolution in the subfamily Gomphrenoideae (Amaranthaceae) (PhD, Cullmann Program for Molecular Systematics Studies, The New York Botanical Garden completed december 2006)
Kerstin Wilhelm: Evolution of african Amaranthaceae (PhD)
Kai Müller: Evolution of Amaranthaceae - A case study integrating molecular phylogenetics and pollen data (PhD - completed december 2005)
Gudrun Kadereit (Universität Mainz), Hilda Flores (Universidad Nacional Autonoma de México), Tim Motley (The New York Botanical Garden), Donald Pratt (Stephen F. Austin State University, Nacogdoches), Helmut Freitag and Kurt Weising (Universität Kassel)
The Lamiales (oregano, deadnettle and relatives) with its 22.000 species is one of the largest angiosperm orders. Still, the relationships of the Lamiales backbone are largely unknown. Recently, the analysis of non-coding and fast evolving genomic regions has yielded some progress, indicating Plocospermataceae and Oleaceae branch first, followed by families such as Calceolariaceae, Gesneriaceae, Gratiolaceae and Plantaginaceae. Here we aim at further utilizing non-coding DNA to eventually resolve the Lamiales tree. Among the lineages of Lamiales, extreme differences in mutational rates occur. This has first been observed in the parasitic Orobanchaceae and now also in the carnivourous Lentibulariaceae. Mutational rates and possible factors governing them are important issues in analysing the evolutionary diversification of the Lamiales.
Current efforts aim to better understand the molecular evolution of group II introns in asterids.
Karsten Salomo (diploma)
Andreas Wilm (Universität Düsseldorf)