| Claus-Peter Stelzer | |||||||||
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2006 – Research Scientist at the Institute of Limnology, Mondsee 2003 – 2005 Lecturer (Wissenschaftlicher Assistent); University of Münster (Germany) 2001 – 2003 Postdoctoral Research Associate; Georgia Institute of Technology, Atlanta (USA) 1995 – 2000 MSc and PhD Thesis at the Max-Planck Institute of Limnology, Plön (Germany) 2000 PhD in Zoology/Limnology; University of Kiel (Germany) 1996 MSc (Diplom) in Biology; University of Ulm (Germany) |
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| Research | |||||||||
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I am interested in various topics at the intersection of ecology and evolution. In my research I use rotifers as model organisms for experimental studies at the individual and population level. Rotifers are ideally suited for this, because populations of thousands can be kept in small containers in the lab, while single individuals can still be handled conveniently. Their short generation times allow experimental investigations of individual life history patterns as well as population studies on microevolution over dozens of generations. For genetic characterization I mainly use DNA barcoding (COI and ITS1 genes) and AFLPs.
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Evolution of (a)sexThe ubiquity of sexual reproduction is an evolutionary puzzle because asexuality should confer major theoretical advantages. I am studying this problem from various angles, for instance concerning the mechanism of asexual origins or the evolutionary and ecological consequences of obligate asexuality. As model system I use the rotifer Brachionus calyciflorus, which normally uses a mixed reproductive mode (sexual and asexual reproduction), but can occasionally gives rise to obligately asexual lineages. Together with my team I have recently discovered that obligate asexuality in B. calyciflorus is inherited in a simple Mendelian fashion: Obligate asexuals are homozygous for a recessive allele, which causes inability to respond to the chemical signals that normally induce sexual reproduction in this species (Fig. 1). Interestingly, obligate parthenogens are also dwarfs (approximately 50% smaller than cyclical parthenogens), indicating pleiotropy or linkage with genes that strongly affect body size. I have recently quantified the “cost of sex” in this system and found that obligate asexuals can have substantial short-term fitness advantages and displace populations of sexuals within only a few days. This calls for explanations on how sexual reproduction is stabilized in this system. We are currently addressing various hypotheses on the maintenance of sex in this system in lab experiments. Representative publications: |
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Genome size evolutionGenome size, measured as the haploid nuclear DNA content (C-value), is extremely variable among eukaryotes. In the last decades it has become clear that the observed genome size variation is largely caused by differences in the content of non-coding and/or repetitive DNA, such as introns, pseudogenes, or transposable elements. Nevertheless, there are still many unanswered questions about genome size diversity, such as the actual causes driving the differences in DNA content, speed and mode of changes in genome size over population genetic and longer evolutionary time scales, or the cellular and organismal consequences of large vs. small genome size. I have recently established the flow cytometry method for measuring genome sizes in rotifers (example, see (Fig. 2). So far, the results indicate that rotifer genomes are rather small in comparison to most metazoans (C-values ranging from 0.06 to 0.416pg). In a comparative study of the Brachionus plicatilis complex, we have found an unexpectedly high variation even among closely related species (up to 7-fold), and indications of whole-genome duplications in this species complex. My future work will address the significance of intraspecific genome size variation within populations, as well as the question whether such variation can be experimentally selected over microevolutionary time scales. Representative publications: | |||||||||
Sexual signals & speciationI am also interested in sexual signals and their divergence during and after speciation. Since my time as postdoc in Terry Snell’s lab (http://www.biology.gatech.edu/people/terry-snell), I have worked on mate recognition and sexual induction in Brachionus rotifers. For instance, we found that the induction of sexual reproduction in Brachionus plicatilis is mediated by a protein that is secreted into the water at high population densities. In a comparative study of the Brachionus plicatilis complex we found evidence for evolutionary stasis of this signal, as even distantly related species could cross-induce sex among each other. Similar to sex induction, mate recognition is also mediated by proteins in Brachionus. We have developed a protocol by which such proteins can be removed from the body surface and transferred among species, or isolated and characterized biochemically. Terry Snell and co-workers have continued on this line of research and have recently succeeded in characterizing the protein sequence of the mate recognition protein. Representative publications: |
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Life history evolutionI am interested in resource allocation patterns and the resulting physiological trade offs between somatic growth, survival and reproduction. My main model organism for such questions has been the rotifer Synchaeta pectinata, a very common and widespread rotifer in the plankton of large lakes. Synchaeta has a completely transparent body surface, which makes it easy to study the dynamics of nutritive tissues within individuals. This experimental approach allowed inferring temporally variable allocation schemes, e.g. the adjustment of reproductive effort in response to variable resource abundances. I have also worked on the problem of “Bergmann’s rule in ectothermes”, the observation that many invertebrates exhibit temperature clines in body size (they reach higher adult body sizes at low temperatures). In Synchaeta females do not only grow to larger body sizes at low temperatures, they also invest more into individual offspring, which additionally increases body size in the next generation. Representative publications: |
 Synchaeta pectinata female |
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Method development In the last years I have developed and refined several methods for experimentation with rotifers. Most of these applications were targeted to either experimental evolution and/or population ecology. One example is an automated system for sampling, counting, and biological analysis of rotifer populations (Fig. 3). This system uses computer-aided image analysis and allows sampling up to 40 independent rotifer populations at intervals of a few hours. It counts females and males in these populations, and estimates body size distributions automatically. The system makes use of the most recent advances in digital imaging and contains hardware components that are also found in industrial production control. Most recently, I also have developed an inexpensive slow-rate cooling device, which uses Peltier-elements instead of liquid nitrogen. It allows endpoint temperatures of less than -40°C, while allowing controlled cooling rates as low as 0.1°C/min. This device is aimed at cryopreservervation of clonal lines in the rotifer Brachionus plicatilis for studies in experimental evolution. Stelzer, C.P. (2009) Automated system for sampling, counting, and biological analysis of rotifer populations. Limnol. Oceanogr. Methods7: 856-864. |
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| Staff | |||||||||
Sabine Ullrich (Laboratory technician) Peter Stadler (Laboratory technician) Thomas Scheuerl (PhD) Simone Riß (Postdoc) - on maternity leave |
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| Projects | |||||||||
Austrian Science Fonds (FWF 20735-B17) "Evolution of asexuality in experimental rotifer populations" (PI: Claus-Peter Stelzer) |
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| Teaching | |||||||||
2003-2006: since 2007: |
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| Publications | |||||||||
| 2012 Stelzer, C.P. (2012) Population regulation in sexual and asexual rotifers: an eco-evolutionary feedback to population size? Functional Ecology, 26, 180–188. PDF 2011 Scheuerl, T., Riss, S., Stelzer, C.P. (2011). Phenotypic effects of an allele causing obligate parthenogenesis in a rotifer. Journal of Heredity. PDF Stelzer, C.P., Riss, S., Stadler, P. (2011) Genome size evolution at the speciation level: The cryptic species complex Brachionus plicatilis (Rotifera) BMC Evolutionary Biology 11: 90. PDF Stelzer, C.P. (2011). A first assessment of genome size diversity in Monogonont rotifers. Hydrobiologia 662: 77–82 PDF Stelzer, C.P. (2011). The cost of sex and competition between cyclical and obligate parthenogenetic rotifers. American Naturalist 177 (2): E43-E53. PDF 2010 Stelzer, C.P., Schmidt, J., Wiedlroither, A., Riss, S. (2010) Loss of Sexual Reproduction and Dwarfing in a Small Metazoan. PLoS ONE 5(9): e12854. doi:10.1371/journal.pone.0012854. PDF 2009 Stelzer, C.P. (2009) Automated system for sampling, counting, and biological analysis of rotifer populations. Limnol. Oceanogr. Methods 7: 856-864. PDF 2008 Stelzer, C.P. (2008): Obligate asex in a rotifer and the role of sexual signals. Journal of Evolutionary Biology 21 (1): 287–293. PDF 2006 Stelzer, C.P. (2006): "Changes in the competitive abilities of two planktonic rotifer species at different temperatures: an experimental test." Freshwater Biology 51: 2187-2199. PDF Timmermeyer, N. and Stelzer, C.P. (2006): "Induction of sexual reproduction in Synchaeta tremula (Rotifera, Monogononta)." Journal of Plankton Research 28: 1233-1239. PDF Snell, T.W., Kubanek, J.,Carter, W. , Payne, A. B., Kim, J., Hicks, M., and Stelzer, C.P. (2006): "A protein signal triggers sexual reproduction in Brachionus plicatilis (Rotifera)." Marine Biology 149: 763-773. PDF Stelzer, C.P. and Snell, T.W. (2006): "Specificity of the crowding response in the Brachionus plicatilis species complex." Limnology and Oceanography 51: 125-130. PDF Stelzer, C.-P. (2006) Competition between two planktonic rotifer species at different temperatures: an experimental test. Freshwater Biology *51* (12), 2187-2199. PDF 2005 Snell, T.W. and Stelzer, C.P. (2005): "Removal of surface glycoproteins and transfer among Brachionus species." Hydrobiologia 546: 267-274. PDF Stelzer, C.P. (2005): "Evolution of rotifer life histories." (Review) Hydrobiologia 546: 335-346. PDF 2003 Stelzer, C.P. and Snell, T.W. (2003): "Induction of sexual reproduction in Brachionus plicatilis (Monogononta, Rotifera) by a density-dependent chemical cue." Limnology and Oceanography 48: 939-943. PDF 2002 Stelzer, C.P. (2002): "Phenotypic plasticity of body size at different temperatures in a planktonic rotifer: mechanisms and adaptive significance." Functional Ecology 16: 835-841. PDF 2001 Stelzer, C.P. (2001): "Resource limitation and reproductive effort in a planktonic rotifer." Ecology 82: 2521-2533. PDF 2000 Boersma, M. and Stelzer, C.P. (2000): "Response of a zooplankton community to the addition of unsaturated fatty acids: an enclosure study." Freshwater Biology 45: 179-188. PDF 1998 Stelzer, C.P. (1998): "Feeding behaviour of the rotifer Ascomorpha ovalis: functional response, handling time and exploitation of individual Ceratium cells." Journal of Plankton Research 20: 1131-1144. PDF Stelzer, C.P. (1998): "Population growth in planktonic rotifers: Does temperature shift the competitive advantage for different species?" Hydrobiologia 387/388: 349-353. PDF |
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