September 1, 2012 - present: Research Scientist at the Research Department for Limnology, Mondsee of the University of Innsbruck; "Privatdozent" at the University of Salzburg (since 2012)
2006 - August 31, 2012: Research Scientist at the Institute of Limnology, Mondsee; "Privatdozent" at the University of Salzburg (since 2012)
2012: Habilitation (venia legendi) in Evolutionary Ecology; University of Salzburg (Austria)
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)
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.
Evolution of (a)sex
The 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: Stelzer, C.P. (2008) Obligate asex in a rotifer and the role of sexual signals. Journal of Evolutionary Biology 21 (1): 287–293. 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. Stelzer, C.P. (2011). The cost of sex and competition between cyclical and obligate parthenogenetic rotifers. American Naturalist 177(2): E43-E53.
Genome size evolution
Genome 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: Stelzer, C.P. (2011). A first assessment of genome size diversity in Monogonont rotifers. Hydrobiologia 662: 77–82. Stelzer, C.P., S. Riss, P. Stadler (2011). Genome size evolution at the speciation level: The cryptic species complex Brachionus plicatilis. BMC Evolutionary Biology 11:90.
Sexual signals & speciation
Brachionus plicalilis female with dwarf male (Photograph courtesy of T.W. Snell and G. Melone).
I 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: 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. 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. Snell, T.W. and Stelzer, C.P. (2005): "Removal of surface glycoproteins and transfer among Brachionus species." Hydrobiologia 546: 267-274.
Life history evolution
Synchaeta pectinata female
I 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: 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. Stelzer, C.P. (2001): "Resource limitation and reproductive effort in a planktonic rotifer." Ecology 82: 2521-2533.
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.
Austrian Science Fonds (FWF P26256) "Mechanisms and significance of genome size variation in rotifers" (PI: Claus-Peter Stelzer) 2014 - 2018
Abstract. Despite an explosive increase of genomic information during the last ten years, the ultimate causes of genome size variation in eukaryotes are still controversial. At the core of this controversy is the puzzling genome size variation across eukaryotic taxa, which spans approximately five orders of magnitude. In this project we aim to investigate the mechanisms and significance of genome size variation at short evolutionary timescales, such as variation among closely related species, among populations, and among individuals within a population. Intrapopulation genome size variation can be a powerful test bed for analyzing the ultimate causes of genome size evolution, because it allows studying the effects of changes in genome size in a relatively homogeneous genomic background.
Our model system is the facultative (a)sexual rotifer Brachionus plicatilis, a cryptic species complex consisting of at least 14 closely related species. Within this complex we will focus on the so-called ‘Austria’-lineage, which has undergone a 1.9-3.5 fold increase in genome size relative to its sister-species. Furthermore, we will study in detail the OHJ-population, a population from “Obere Halbjochlacke” (a small alkaline water body near Illmitz, Lower Austria) within the ‘Austria’-lineage, which exhibits a remarkable 25% (1.25 fold) variation in genome size.
Specifically, we propose the following aims: (1) Elucidate the mechanisms of genome size variation by comparative genome sequencing (i) between the ‘Austria’-lineage and its sister species, (ii) among populations within the ‘Austria’-lineage, (iii) within the OHJ-population, (2) to experimentally determine how variation in genome size is maintained in the OHJ-population and inherited during sexual reproduction, and (3) to test assumptions and predictions of general hypotheses on genome size evolution using intrapopulation genome size variation of the OHJ-population. Specifically, we will address the following assumptions and predictions: (i) Genome size variation at the population level significantly covaries with cell size, body size and egg development time, (ii) Clones with large genome size accumulate deleterious mutations faster than clones with small genome size, and (iii) Clones with small genome size are favored by selection for maximum population growth rates under nutrient limitation.
We expect that the proposed work will contribute new and general insights into the mechanisms and ultimate causes of genome size variation. Our model system B. plicatilis offers an exceptionally broad methodology, including population-level experiments across many generations owing to its short life cycle, which is unparalleled by most current model organisms in genome size evolution. In addition, the proposed project would contribute new genomic data on an important understudied invertebrate.
Austrian Science Fonds (FWF 20735-B17) "Evolution of asexuality in experimental rotifer populations" (PI: Claus-Peter Stelzer) 2008-2012
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.
Stelzer C.P., Pichler M., Hatheuer, A. (2021). Linking genome size variation to population phenotypic variation within the rotifer, Brachionus asplanchnoidis. Commun Biol 4:596, https://doi.org/10.1038/s42003-021-02131-z
2020
Schärer L., J. N., Brand, P., Singh K., Zadesenets S., Stelzer C.-P., Viktorin G. (2020). A phylogenetically informed search for an alternative Macrostomum model species, with notes on taxonomy, mating behavior, karyology and genome size. Journal of Zoological Systematics and Evolutionary Research 58:41–65,DOI: 10.1111/jzs.12344
2019
Scheuerl T., Stelzer C.-P. (2019). Asexual reproduction changes predator population dynamics in a life predator-prey system. Population Ecology 61:210–216, doi.10.1002/pope.1017
Stelzer C.-P., Pichler M., Stadler P., Hatheuer A., Riss S. (2019): Within-population genome size variation is mediated by multiple genomic elements that segregate independently during meiosis. Genome Biology and Evolution, evz253, https://doi.org/10.1093/gbe/evz253
Pjeta R., Wunderer J., Bertemes P., Hofer T., Salvenmoser W., Lengerer B.; Coassin S., Erhart G, Beisel C., Sobral D., Kremser L., Lindner H, Curini-Galletti M., Stelzer C.P. , Hess M.W., Ladurner P. (2019). Temporary adhesion of the proseriate flatworm Minona ileanae. Phil. Trans. R. Soc. B 374:1784. doi/org/10.1098/rstb.2019.0194
Blommaert J., Riss S., Hecox-Lea B., Mark Welch D.B., Stelzer C.-P. (2019). Small, but surprisingly repetitive genomes: transposon expansion and not polyploidy has driven a doubling in genome size in a metazoan species complex. BMC Genomics 20: 466, doi.org/10.1186/s12864-019-5859-y
2017
Riss S., Arthofer W., Steiner F.M., Schlick-Steiner B.C., Pichler M., Stadler P., Stelzer C.-P. (2017). Do genome size differences within Brachionus asplanchnoidis (Rotifera, Monogononta) cause reproductive barriers among geographic populations? Hydrobiologia, 796(1): 59-75. doi:10.1007/s10750-016-2872-x
Stelzer C.P. (2017). Extremely short diapause in rotifers and its fitness consequences. Hydrobiologia, 796(1): 255-264. doi 10.1007/s 10750-016-2937-x
Mills S., Alcántara-Rodríguez J.A., Ciros-Pérez J., Gómez A., Hagiwara A., Hinson Galindo K., Jersabek C.D., Malekzadeh-Viayeh R., Leasi F., Lee J.-S., Welch D.B.M., Papakostas S., Riss S., Segers H., Serra M., Shiel R., Smolak R., Snell R.L., Stelzer C.-P., Tang C.Q., Wallace R.L., Fontaneto D., Walsh E.J. (2017). Fifteen species in one: deciphering the Brachionus plicatilis species complex (Rotifera, Monogononta) through DNA taxonomy. Hydrobiologia 796(1): 39-58, doi 10.1007/s10750-016-2725-7. PDF
Scheuerl T., Stelzer C.-P. (2017). Sex initiates adaptive evolution by recombination between beneficial loci. PLoS ONE 12(6): e0177895. doi.org/10.1371/journal.pone.0177895
Stelzer C.P., Lehtonen J. (2017) Diapause and maintenance of facultative sexual reproductive strategies. Phil. Trans. R. Soc. B 371: 20150536. doi.org/10.1098/rstb.2015.0536
Michaloudi E., Mills S., Papakostas S., Stelzer C.-P., Triantafyllidis A., Kappas I., Vasileiadou K., Proios K., Abatzopoulos T.J. (2016). Morphological and taxonomic demarcation of Brachionus asplanchnoidis Charin within the Brachionus plicatilis cryptic species complex (Rotifera, Monogononta). Hydrobiologia, doi 10.1007/s10750-016-2924-2
2015
Stelzer, C.-P. (2015). Does the avoidance of sexual costs increase fitness in asexual invaders? Proc Natl Acad Sci USA,doi: 10.1073/pnas.1501726112
2014
Routtu J., Hall D. M., Albere B., Beisel C., Bergeron D. R., Chaturvedi A., Choi J.-H., Colbourne J., De Meester L., Stephens T. M., Stelzer C.-P., Solorzano E., Thomas K. W., Pfrender E. M., Ebert D. (2014). An SNP-based second-generation genetic map of Daphnia magna and its application to QTL analysis of phenotypic traits. BMC Genomics 15:1033. Doi:10.1186/1471-2164-15-1033
2013
Scheuerl T., Stelzer C.P. (2013) Patterns and dynamics of rapid local adaptation and sex in varying habitat types in rotifers. Ecology and Evolution. DOI: 10.1002/ece3.781
Hanson, S.J., Stelzer, C.P., Welch, D.B., Logsdon, J.M. (2013) Comparative transcriptome analysis of obligately asexual and cyclically sexual rotifers reveals genes with putative functions in sexual reproduction, dormancy, and asexual egg production. BMC Genomics 14(1): 412. DOI: 10.1186/1471-2164-14-412
Hanson, S. J.,Schurko, A. M., Hecox-Lea, B., Mark Welch, D. B., Stelzer, C. P., Logsdon Jr., J. M. (2013) Inventory and Phylogenetic Analysis of Meiotic Genes in Monogonont Rotifers. J Hered. 104(3): 357-370. doi:10.1093/jhered/est011
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
Stelzer, C.P. (2012) Evolutionary Ecology of Rotifers. Habilitation Thesis PDF
2011
Scheuerl, T., Riss, S., Stelzer, C.P. (2011). Phenotypic effects of an allele causing obligate parthenogenesis in a rotifer. Journal of Heredity 102(4): 409-415. 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
