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Dr. C.J.M. (Martijn) Egas

Universitair Hoofddocent Evolutie en Gedrag
Faculteit der Natuurwetenschappen, Wiskunde en Informatica
Institute for Biodiversity and Ecosystem Dynamics
Fotograaf: onbekend

  • Science Park 904
  • Kamernummer: C3.214
  • Postbus 94240
    1090 GE Amsterdam
  • Profile
    Visit the website of the research institute IBED


    Welcome to my personal webpages at the University of Amsterdam.
    I am associate professor in Evolution and Behaviour at the Institute for Biodiversity and Ecosystem Dynamics.
    Currently, I am supervising one PhD student:

    • Dajo Boog


    Graduated PhD students:

    • Pedro Branco (thesis defence: October 2021)
    • Bram Knegt (thesis defence: June 2019)
    • Alexandra Revynthi (thesis defence: December 2017)
    • Paulien de Bruijn (thesis defence: June 2015)
    • Eva van den Broek (thesis defence: January 2014)
    • Mathias Spichtig (thesis defence: June 2013)
    • Nicola Tien (thesis defence: November 2010)
    • Beata Sznajder (thesis defence: September 2010)


    Please do refer to the information on my research, teaching activities and publications, which can be accessed through the links below.

    Overview of the Department of Evolutionary and Population Biology
  • Research



    Generally, I am interested in social evolution and multi-level selection, and have worked on projects related to: effects of learning on the evolution of exploitation strategies of mite predators (with Beata Sznajder; PhD awarded September 2010), evolution of prudent predation in the predatory mite Phytoseiulus persimilis (with Alexandra Revynthi; PhD awarded December 2017), evolution of diapause (with Annemarie Kroon, postdoc), communicating the nature of danger in thrips (with Paulien de Bruijn - see also below; PhD awarded June 2015), and evolution of the interaction between cytoplasmic bacteria and the animal hosts they infect (with Filipa Vala and Hans Breeuwer). More recently, I have also worked on alternative male mating tactics in the two-spotted spider mite, Tetranychus urticae, with Yukie Sato. My research focus is in the combined experimental and theoretical study of evolutionary dynamics (i.e., feedbacks between evolutionary and ecological processes - nowadays called eco-evolutionary dynamics - and the role of genetic factors in determining these dynamics). In this context I have worked with various collaborators on 1) the evolution of specialization in herbivorous arthropods, and 2) the evolution of cooperation and altruism in humans and arthropods.

    Specialization is a widespread biological phenomenon, particularly among herbivorous arthropods, and its evolutionary explanation therefore poses important questions. With Sara Magalhaes (University of Lisbon) and Isabelle Olivieri (University of Montpellier), I studied patterns of local adaptation to new host plants using an experimental evolution approach with T. urticae. Our main findings were that local adaptation builds up trade-offs between performance on two new host plants and that phenotypic plasticity (in the form of maternal effects) plays a large role in the evolutionary response to new host plants. With Nicola Tien (PhD awarded November 2010), I studied the evolutionary genetics of life-history traits of T. urticae, such as development time, juvenile survival or egg-laying rate. Of all life-history traits, egg-laying rate stood out as a trait with high additive genetic variance (resulting in a high degree of heritability) as well as strong effects of (partly recessive) deleterious variation. The latter finding suggests that host-plant specialization in this species may be explained by “mutation accumulation” rather than fitness trade-offs, a theoretical possibility that has not been tested in herbivorous arthropods. With Bram Knegt (PhD awarded June 2019) I studied aspects of host plant specialization of the spider mite Tetranychus evansi, which is on record as a specialist on solanaceous plants. We assessed genetic variation in the ability of this mite to suppress direct defence mechanisms in its host plant tomato.

    Explaining the evolution and maintenance of cooperation among unrelated individuals is one of the fundamental problems in biology and the social sciences. To study this problem, I have collaborated with Aljaz Ule, Eva van den Broek, Matthijs van Veelen and Arthur Schram (Experimental Economics, UvA) and Arno Riedl (Behavioural Economics, Maastricht University) to study the interactive evolution of social norms and cooperation. Experiments confirmed a role for group competition in within-group cooperation. Also, we showed that humans use both personal experience and reputation information about others in helping decisions, and that humans show distinct moral rules in assessing reputation information (with Eva van den Broek, PhD awarded January 2014, and Lucas Molleman, PhD awarded at Groningen University, February 2014). Theoretical study focused on the role of mutation in the maintenance of cooperation by direct reciprocity, and on sexual selection for cooperative behaviour (with Mathias Spichtig, PhD awarded June 2013). More recently, we collaborate with Evolutionary Psychologist Annemie Ploeger in a project to study sexual selection on altruistic behaviour (with PhD student Dajo Boog). I also study spiteful behaviour (male killing) in social spider mites (with Yukie Sato), and alarm communication in thrips (with Paulien de Bruijn, PhD awarded June 2015). We have shown that thrips larvae exhibit context-dependent communication of predation danger (relating to predator nearby vs actual predator attack) by means of varying the ratio of two chemical components in their alarm pheromone, and showing appropriate responses to the various alarm signals. We also showed that thrips larvae can recognize kin. Taken together this means that we now have a lab system for studying the evolutionary mechanisms that in theory can maintain such a communication system, a topic of general interest that is so far only investigated in prairie dogs, ground squirrels and several other mammals under natural conditions.

    My expertise in both theory and experiments on specialization has led to collaboration with the group of Jef Huisman (Aquatic Microbiology, University of Amsterdam) on the evolution of specialization and life-history traits in phytoplankton and their herbivores (with Jef Huisman). This collaboration also resulted in daily supervision of one of the PhD students of Jef Huisman (Pedro Branco, PhD awarded October 2021) on evolution of ecological stochiometric relationships in phytoplankton and zooplankton.

  • Teaching


    I am involved in the following courses and other teaching activities:

    Bachelor programme Biology

    • Course: "Neurobiology and Behaviour" (for biologists)
    • Course: "Evolutionary Biology" (for biologists)
    • Course: "Dynamical Systems in Biology" (for biologists)
    • Course: "Evolution and Behaviour" (for psychobiologists)
    • Literature thesis supervision
    • Bachelor thesis supervision

    Master programme Biological Sciences

    • Coordinator of the MSc track General Biology
    • Courses: "Masterclasses in Ecology & Evolution", involved in "Experimental Design and Analysis"
    • Supervision of MSc projects and literature theses

    PhD courses

    • "Evolutionary Dynamics"


    • Chairman Examination Board Earth and Life Sciences (2020-present)
    • Chairman IBED Advisory Committee on Teaching and Education (IBED-ACTE) (2017-present)


  • Publicaties


    • Kobayashi, H., Sato, Y., & Egas, M. (2022). Males mate with females even after sperm depletion in the two-spotted spider mite. Experimental & Applied Acarology. https://doi.org/10.1007/s10493-022-00706-x
    • Revynthi, A. M., Verkleij, D., Janssen, A., & Egas, M. (2022). Artificial selection for timing of dispersal in predatory mites yields lines that differ in prey exploitation strategies. Ecology and Evolution, 12(3), [e8760]. https://doi.org/10.1002/ece3.8760






    • Knegt, B., Potter, T., Pearson, N. A., Sato, Y., Staudacher, H., Schimmel, B. C. J., Kiers, E. T., & Egas, M. (2017). Detection of genetic incompatibilities in non-model systems using simple genetic markers: hybrid breakdown in the haplodiploid spider mite Tetranychus evansi. Heredity, 118(4), 311-321. https://doi.org/10.1038/hdy.2016.103 [details]









    • Magalhães, S., Blanchet, E., Egas, M., & Olivieri, I. (2009). Are adaptation costs necessary to build up a local adaptation pattern? BMC Evolutionary Biology, 9, 182. https://doi.org/10.1186/1471-2148-9-182 [details]
    • Tien, N. S. H., Sabelis, M. W., & Egas, M. (2009). Heritability of defence and life-history traits in the two-spotted spider mite. Evolutionary Ecology Research, 11(8), 1271-1281. [details]


    • Egas, M., & Riedl, A. (2008). The economics of altruistic punishment and the maintenance of cooperation. Proceedings of the Royal Society B-Biological Sciences, 275(1637), 871-878. https://doi.org/10.1098/rspb.2007.1558 [details]
    • Kroon, A., Veenendaal, R. L., Bruin, J., Egas, M., & Sabelis, M. W. (2008). "Sleeping with the enemy"—predator-induced diapause in a mite. Naturwissenschaften, 95(12), 1195-1198. https://doi.org/10.1007/s00114-008-0442-4 [details]
    • Stomp, M., van Dijk, M. A., van Overzee, H. M. J., Wortel, M. T., Sigon, C. A. M., Egas, M., ... Huisman, J. (2008). The timescale of phenotypic plasticity and its impact on competition in fluctuating environments. American Naturalist, 172(5), E169-E185. https://doi.org/10.1086/591680 [details]


    • Sabelis, M. W., van Baalen, M., Bakker, FM., Bruin, J., Drukker, B., Egas, C. J. M., ... Brown, VK. (Ed.) (1998). Evolution of direct and indirect plant defence against herbivorous arthropods. In Herbivores: Between Plants and Predators (pp. 109-166). London: Blackwell.


    • Branco, P., Egas, M., Elser, J. J., & Huisman, J. (2021). Correction to: Eco-evolutionary dynamics of ecological stoichiometry in plankton communities” (American Naturalist 192: E1–E20). American Naturalist, 197(4). https://doi.org/10.1086/713285



    • Knegt, B., Alba, J. M., Ataide, L. M. S., Barbosa, T. A., Bernardo, A. M. G., Chafi, R., ... Egas, M. (2017). Meta-analysis reveals intraspecific variation in herbivores for plant-mediated interactions. Poster session presented at Gordon Research Conference "Plant - Herbivore Interactions", Ventura, CA, USA, United States.


    • Blankers-, T., Bisschop, K., Groot, A. & Egas, M. (2020). NWA Small Project Call.


    • Egas, M. (editor) (2020-2026). ANIMAL BIOLOGY (Journal).


    • Egas, C. J. M., Janssen, A. & Revynthi, A. (8-3-2022). Artificial selection for dispersal results in lines with different exploitation strategies. Universiteit van Amsterdam. https://doi.org/10.21942/uva.19322555.v1


    • Egas, M., Sato, Y., Gotoh, T., Fujiwara, S. & Matsuda, T. (1-1-2021). Additional file 2 of Patterns of reproductive isolation in a haplodiploid mite, Amphitetranychus viennensis: prezygotic isolation, hybrid inviability and hybrid sterility. figshare Academic Research System. https://doi.org/10.6084/m9.figshare.16664386.v1
    • Matsuda, T., Sato, Y., Gotoh, T., Egas, M. & Fujiwara, S. (1-1-2021). Additional file 3 of Patterns of reproductive isolation in a haplodiploid mite, Amphitetranychus viennensis: prezygotic isolation, hybrid inviability and hybrid sterility. figshare Academic Research System. https://doi.org/10.6084/m9.figshare.16664389.v1
    • Egas, M., Fujiwara, S., Sato, Y., Matsuda, T. & Gotoh, T. (1-1-2021). Additional file 1 of Patterns of reproductive isolation in a haplodiploid mite, Amphitetranychus viennensis: prezygotic isolation, hybrid inviability and hybrid sterility. figshare Academic Research System. https://doi.org/10.6084/m9.figshare.16664383.v1
    • Gotoh, T., Fujiwara, S., Egas, M., Sato, Y. & Matsuda, T. (1-1-2021). Patterns of reproductive isolation in a haplodiploid mite, Amphitetranychus viennensis: prezygotic isolation, hybrid inviability and hybrid sterility. figshare Academic Research System. https://doi.org/10.6084/m9.figshare.c.5630047.v1



    • Revynthi, A. M., Egas, M., Janssen, A. & Sabelis, M. W. (1-11-2018). Data from: Prey exploitation and dispersal strategies vary among natural populations of a predatory mite. DRYAD. https://doi.org/10.5061/dryad.8hs46jv
    • Gotoh, T., Mochizuki, A., Egas, M., Sakamoto, H., Sato, Y., Chao, J.-T. & Saito, Y. (1-6-2018). Data from: Patterns of reproductive isolation in a haplodiploid – strong post‐mating, prezygotic barriers among three forms of a social spider mite. DRYAD. https://doi.org/10.5061/dryad.354f92m


    • Kiers, E. T., Sato, Y., Knegt, B., Staudacher, H., Egas, M., Potter, T., Schimmel, B. C. J. & Pearson, N. A. (1-4-2017). Data from: Detection of genetic incompatibilities in non-model systems using simple genetic markers: hybrid breakdown in the haplodiploid spider mite Tetranychus evansi. DRYAD. https://doi.org/10.5061/dryad.0j4m5
    This list of publications is extracted from the UvA-Current Research Information System. Questions? Ask the library or the Pure staff of your faculty / institute. Log in to Pure to edit your publications. Log in to Personal Page Publication Selection tool to manage the visibility of your publications on this list.
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