Fotograaf: FNWI

dhr. A.J. (Bram) Knegt MSc

  • Faculteit der Natuurwetenschappen, Wiskunde en Informatica
  • Bezoekadres
    Science Park A
    Science Park 904  Amsterdam
    Kamernummer: C3.218
  • Postadres:
    Postbus  94248
    1090 GE  Amsterdam
    T: 0205257702

I started my PhD in December 2012, supervised by dr. Martijn Egas. My research focuses on the plant-eating arthropod Tetranychus evansi - a spider mite. This spider mite species originated in South America but has recently become an invasive species in many parts of the world. The rapid spread of this species is of concern for agriculture, because it likes to eat many commercially grown crops, such as tomato, potato, aubergine and pepper. 

One reason why T. evansi can so easily infest these plants is that it can suppress their defense. The exact mechanism behind this is unknown, but it causes the infested plants to be very edible compared to other plants. Upon infestation, the spider mites quickly multiply, and cover the plant with dense webbing. Within 2-3 weeks the plant dies, and the mites disperse to find new host plants.

Suppression of plant defense is not new for science, but the extent to which T. evansi can suppress plant defense is unprecedented. Why is T. evansi so keen on suppressing plant defense? What evolutionary forces have driven this species to become such an aggressive suppressor? In my research I aim to find answers to these questions.

Tetranychus evansi female (left) and male (right). Picture downloaded from

A.J. (Bram) Knegt MS

PhD Candidate

Population Biology - Institute for Biodiversity and Ecosystem Dynamics

University of Amsterdam


Visiting address

Science Park 904

1098 XH Amsterdam

Room C3.218



a.j.knegt (at)


  • Knegt, B., Jansa, J., Franken, O., Engelmoer, D. J. P., Werner, G. D. A., Bücking, H., & Kiers, E. T. (2016). Host plant quality mediates competition between arbuscular mycorrhizal fungi. Fungal Ecology, 20, 233-240. DOI: 10.1016/j.funeco.2014.09.011 [details] [PDF]
  • Knegt, B., Potter, T., Pearson, N. A., Sato, Y., Staudacher, H., Schimmel, B. C. J., ... Egas, M. (2016). Detection of genetic incompatibilities in non-model systems using simple genetic markers: hybrid breakdown in the haplodiploid spider mite Tetranychus evansi. Heredity. DOI: 10.1038/hdy.2016.103 [details] [PDF]
  • Becking, L. E., de Leeuw, C. A., Knegt, B., Maas, D. L., de Voogd, N. J., Abdunnur, . U., ... Peijnenburg, K. T. C. A. (2016). Highly divergent mussel lineages in isolated Indonesian marine lakes. PeerJ, 4, [e2496]. DOI: 10.7717/peerj.2496 [details] [PDF]


  • Kant, M. R., Jonckheere, W., Knegt, B., Lemos, F., Liu, J., Schimmel, B. C. J., ... Alba, J. M. (2015). Mechanisms and ecological consequences of plant defence induction and suppression in herbivore communities. Annals of Botany, 115(7), 1015-1051. DOI: 10.1093/aob/mcv054 [details] [PDF]


  • Knegt, A. J., Alba Cano, J. M., Silva Ataide, L. M., Barbosa, T. A., Bernardo, A. M. G., Chafi, R., ... Egas, C. J. 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. [details] [PDF]
  • Knegt, A. J., Egas, C. J. M., Kiers, E. T., Alba Cano, J. M., Silva Ataide, L. M., Barbosa, T. A., ... Solis-Vargas, M. (2017). Meta-analysis reveals intraspecific variation for plant-mediated interactions in herbivores. Poster session presented at Gordon Research Seminar, Ventura, United States. [details] [PDF]
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