Points of Interest
"To tree or not to tree?"
How useful are molecular, morphological, and other data sets to reveal evolutionary pathways and systematic relationships within different plant groups, especially at the intrageneric level?
Is phylogentic tree building the prime choice to understand evolution? Does a principally dichotomous evolution generate data containing strictly dichotomous signal?
Is the more information in sequences than current algorithms extract?
Are molecular marker the ultimate tool of systematics and taxonomy?
When does sense start to become nonsense in molecular-based taxonomic and systematic concepts?
Molecular genetics and its impact on palaeobotany.
How can fossils stand against enormous amounts of molecular data?
What is the impact of missing data? Is there solid information in the fossil record, if 95% of 'species' are lost? And how much information can be extracted from the living (via DNA), if they represent a maximum of 2% of life diversity through earth's history?
Plants in Focus
Beeches not beaches, like other geologists (Fagus, Fagaceae)
The beech tree is one of most abundant and successful northern hemispheric trees despite its low number of accepted species (~9); e.g. compared to >200 described species of its relative, the oak (Quercus). Beech trees have conquered large areas since the last glacial period, becoming dominant elements of forests until the formation of 'monocultures', even in absence of a visible anthropogenic impact. Based on the available data from the internal transcribed spacers ITS1 and ITS2, species and individuals are more variable than whole sections or genera of other northern-hemispheric trees, in particular in comparison to oaks or the Betulaceae. This remarkable intrageneric variability correspond to the potential biogeographic history and evolution of the genus.
Link to poster presented in Bochum 2001
Own publications dealing with the evolution and differentiation of beech trees:
T Denk, G Grimm, et al (2002). Plant Syst Evol 232: 213-236.
GW Grimm (2003). Ph.D.thesis, Tübingen. - Link to full text -
T Denk, GW Grimm, V Hemleben (2005). Am J Bot 92: 1006-1016.
GW Grimm, T Denk, V Hemleben (2007). Syst Biodiv 5: xxx-xxx.Link to pre-print proof.
Cycads (order Cycadales)
see also presentation at IOPC-VI in Qinhuangdao, China, 2000.
Maples (Acer, fam. Sapindaceae)
With 124 species (van Gelderen & al 1994, "Maples of the World") maples form the second largest tree genus of the northern hemisphere. Maples exhibit a wide range of morphological features including significant variability and plasticity below the species level, which is exhibiting by the number of discussed subspecies and variants and its horticultural importance (maple cultivars are the basis of any "Japanese Garden"). The fossil record throughout the Tertiary is rich, however, only poorly understood and organized up to now. The internal transcribed spacers ITS1 and ITS2 of the nuclear encoded 35S rRNA genes have been proven to bear a high potential for taxonomic, systematic and phylogenetic purposes as they allow defining species borders and higher taxonomic groups as well as reconstructing details of evolution.
Maples have been subject of my following publications:
GW Grimm (2003). Ph.D. thesis, Tübingen. - Link to full text -
GW Grimm, SS Renner, et al (2006). Evol Bioinform 2: 279-294 - Link to full text -
GW Grimm, T Denk, V Hemleben. Evolutionary History and Systematics of Acer section Acer. Plant Syst Evol
Online Supplement A: Patterns of ITS motif evolution
Online Supplement B: Comprehensive motif table
T Denk, GW Grimm (2005). Bot J Linn Soc 147: 129-157.