2006 – Research Scientist; Institute of Limnology, Mondsee

2003 – 2005 Assistant Professor (Wissenschaftlicher Assistent); University of Münster (Germany)

2001 – 2003 Postdoctoral Research Associate; Georgia Institute of Technology, Atlanta (USA)

1995 – 2000 Diplom and PhD Thesis at the Max-Planck Institute of Limnology, Plön (Germany)

2000 PhD in Zoology/Limnology; University of Kiel (Germany)

The working group “Experimental Evolutionary Ecology” focuses on evolutionary changes within populations and their feedback on ecological processes. Our main model organism is the rotifer Brachionus calyciflorus, a widespread zooplankter that occurs in small ponds and reservoirs. Rotifers of the genus Brachionus are sometimes called the “metazoan microbes”, since their growth rates are among the highest of all metazoans. In that respect, our model system bridges the gap between microbial and animal studies of ecology and evolution.Currently there are two main avenues in our research: First, in the recently funded FWF project P20735-B17 we have started to investigate the mechanisms and evolutionary consequences of transitions from cyclical to obligate parthenogenesis. Such transitions have high general relevance as they occur in many other cyclical parthenogens (e.g. Daphnia) and because they provide a valuable model system to investigate the “paradox of sex”, one of the big unsolved problems in evolutionary biology. Second, we are developing and refining the “toolbox” for experimental evolution using Brachionus. Such efforts comprise the development of automated counting systems, experimental setups for long-term evolution, cryopreservation, and the development of molecular markers (microsatellites). Such tools will allow, for the first time, to experimentally study evolution in a metazoan and will therefore provide a valuable extension to the existing microbial model systems.

Johanna Schmidt (Laboratory technician)

Anneliese Wiedlroither (Laboratory technician)

Thomas Scheuerl (PhD)

Simone Riß (Postdoc)

Austrian Science Fonds (FWF 20735-B17) "Evolution of asexuality in experimental rotifer populations" (PI: Claus-Peter Stelzer)

Abstract. Most multicellular organisms reproduce sexually, despite high costs associated with this reproductive mode (i.e., costs of males, costs of meiosis, costs associated with finding mates or mating itself). In the last three decades this “paradox of sex” has received considerable attention of both theoreticians and empiricists. Nonetheless, a single and universal explanation for the ubiquity of sex has remained elusive. In particular, explanations on the “paradox of sex” are challenged by the existence of organisms that frequently give rise to obligate asexual lineages. Such organisms should constantly face the danger of being displaced by their asexual variants. Hence, what holds these newly arising asexuals at bay? In this project, the monogonont rotifer Brachionus calyciflorus shall be used as a model system to address this question. The Brachionus system is distinct from most previously used animal models, because it allows an experimental approach: Rotifers have generation times of a few days only, they reproduce fast, and transitions to obligate asexuality can occur on time scales of weeks. In addition, rotifers are small and populations of thousands can be easily kept in laboratory, which allows studying evolutionary changes on the population level. The proposed work addresses three main questions: (i) What is the general mechanism of origin of obligate asexuality in Brachionus? (ii) How fit are asexuals compared to their sexual relatives - under which conditions will they spread/decline? (iii) What is the significance of obligate asexuality in field populations of Brachionus? A variety of methods will be used to answer these questions: lab and field experiments, molecular techniques (DNA barcoding, microsatellites), karyological methods, and automated lab cultures (chemostats). The results are expected to yield new insights into the "paradox of sex", particularly in terms of the factors influencing the success/failure of new asexual lineages. In addition, the expected results will likely contribute to a better understanding of the origin of asexuality in bdelloid rotifers, a sister group of monogonont rotifers that has evolved in the absence of sex for millions of years.

2003-2006:
Evolution and Biodiversity of Animals (Zoology course at the introductory level)
Evolutionary and Population Genetics (Lecture)
Biology of Ageing (Experimental laboratory course)
Evolution of Asexual Reproduction (Experimental laboratory course)

since 2007:
Evolution and Biodiversity (Lecture with exercises)

Submitted

Stelzer, C.P. A first assessment of genome size diversity in Monogonont rotifers.

Stelzer, C.P. The cost of sex and competition between cyclical and obligate parthenogenetic rotifers.

2009

Stelzer, C.P. (2009) Automated system for sampling, counting, and biological analysis of rotifer populations. Limnol. Oceanogr. Methods 7: 856-864.

2008

Stelzer, C.P. (2008): Obligate asex in a rotifer and the role of sexual signals. Journal of Evolutionary Biology 21 (1): 287–293.

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.

Timmermeyer, N. and Stelzer, C.P. (2006): "Induction of sexual reproduction in Synchaeta tremula (Rotifera, Monogononta)." Journal of Plankton Research 28: 1233-1239.

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.

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.

2005

Snell, T.W. and Stelzer, CP. (2005): "Removal of surface glycoproteins and transfer among Brachionus species." Hydrobiologia 546: 267-274.

Stelzer, C.P. (2005): "Evolution of rotifer life histories." (Review) Hydrobiologia 546: 335-346.

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.

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.

2001

Stelzer, C.P. (2001): "Resource limitation and reproductive effort in a planktonic rotifer." Ecology 82: 2521-2533.

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.

1998

Stelzer, C.P. (1998): "Population growth in planktonic rotifers: Does temperature shift the competitive advantage for different species?" Hydrobiologia 387/388: 349-353.

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