Jonah Walker

Biography & Research

Jonah Walker

My research focusses on the evolution of animal and plant signals, particularly in the context of speciation and co-evolutionary interactions between species. I combine behavioural experiments in the field and lab with genomic data to get a truly holistic view of the evolutionary process.

I am fascinated by natural history and the ways in which elegant experiments and genetic analysis can be used to explain the diversity of Life around us. I became interested in science as a child while learning about the extraordinary collection of plants which is housed the Oxford Botanic Garden, where I grew up. As an undergraduate in Cambridge I was able to work on a range of projects, including investigating the genetic basis of wing-pattern signalling in Heliconius butterflies in the central American tropics, and the development of pollinator-attracting signals in Hibiscus flowers. My thesis project, supervised by Andrew Tanentzap, explored the rapid phenotypic and genomic evolutionary responses of Canadian freshwater fleas (Daphnia pulicaria) following invasion of the predatory spiny water-flea (Bythotrephes longimanus).

These early experiences focussed my interests on the evolution of signals and sensory systems during biological diversification. After graduating, I joined the African Cuckoos team. Working with Claire Spottiswoode, Tanmay Dixit, and Nick Horrocks, I am investigating whether whether warbler and weaver host species have evolved eggs which are more vulnerable to thermal or UV damage as a consequence of their arms race with brood-parasitic cuckoo finches. This was prompted by observations that darker (red & olive) eggs have been seen popping during especially hot breeding seasons.

Alongside this work, I began a PhD in 2022 in Cambridge with Joana Meier, for which I am studying genomic hybridisation and mating signal evolution in two spectacular biological radiations: the peacock spiders of Australia (Maratus spp.) and the ithomiine butterflies of South America (Maratus & Mechanitis spp.). I have also worked in Switzerland on patterns of hybridisation and colour evolution in wall lizards (Podarcis muralis).

With my dual background in field-based natural history and lab-based genetics, I am passionate about integrating often disparate strands of biological research — genomic, behavioural, and physiological — to explain natural phenomena. I’m always keen to communicate these findings to the public, especially those living in the places where we are so fortunate to conduct our fieldwork.

 

 

Publications

 

  • Livraghi, L., Hanly, J.J., Van Bellghem, S.M., Montejo-Kovacevich, G., van der Heijden, E.S.M., Loh, L.S., Ren, A., Warren, I.A., Lewis, J.J., Concha, C., Hebberecht, L., Wright, C.J., Walker, J.M., Foley, J., Goldberg, Z.H., Arenas-Castro, H., Salazar, C., Perry, M.W., Papa, R., Martin, A., McMillan, W.O. & Jiggins. C.D. 2021 Cortex cis-regulatory switches establish scale colour identity and pattern diversity in Heliconius. eLife 10: e68549.
  • Bladon, A.J., Lewis, M., Bladon, E.K., Buckton, S.J., Corbett, S., Ewing, S.R., Hayes, M.P., Hitchcock, G.E., Knock, R., Lucas, C., McVeigh, A., Menéndez, R., Walker, J.M., Fayle, T.M. & Turner, E.C. 2020 How butterflies keep their cool: Physical and ecological traits influence thermoregulatory ability and population trends. Journal of Animal Ecology, 89: 2440-2450. 

News

Evolutionary Biology Crash Course

Tanmay Dixit was a member of a team organising and lecturing in the inaugural Evolutionary Biology Crash Course. This course, aimed at undergraduate or early-postgraduate students, teaches evolutionary principles to students who have had limited opportunities to be exposed to evolutionary ideas. The course is funded by the Equal Opportunities Initiative Fund of the European Society of Evolutionary Biology (ESEB). Tanmay presented lectures on behavioural ecology and evolution, focussing on kin selection, coevolution, and parasitism. Over 700 students, with the vast majority from the global South, attended the course, which was a resounding success!

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New paper on visual complexity & mimicry

Our paper “Visual complexity of egg patterns predicts egg rejection according to Weber’s Law” has just been published in the journal Proceedings of the Royal Society B. This research was led by Tanmay Dixit, and carried out together with Andrei Apostol, Kuan-Chi Chen, Tony Fulford, Chris Town and Claire Spottiswoode, in a collaboration between biologists and computer scientists. We used machine learning to compute a biologically-relevant measure of egg pattern complexity, and combined this with field experiments in Zambia to investigate how complexity evolves in an arms race between host egg signatures (by tawny-flanked prinias) and parasitic egg forgeries (by cuckoo finches).

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Fieldwork and teaching at APLORI, Nigeria

Dr Gabriel Jamie is continuing his fieldwork on the evolution of polymorphisms in cisticolas and prinias in Nigeria, where he is also a teaching fellow at the AP Leventis Ornithological Research Institute (APLORI). The image shows the 2022 APLORI MSc class during the Global Birding Big Day on 14 May. The team recorded 135 species while walking around the nature reserve surrounding the institute.

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New paper on the genetics of cuckoo finch egg mimicry

Our paper “Genetic architecture facilitates then constrains adaptation in a host-parasite coevolutionary arms race” has been published in the Proceedings of the National Academy of Sciences of the USA. In it, we address the long-standing puzzle of how exquisite mimicry of the eggs of several different host species can evolve within a single species of brood-parasitic bird. We show that in cuckoo finches in Zambia, egg mimicry of different host egg phenotypes is maternally inherited, which allows mothers to transmit host-specific adaptations to their daughters irrespective of which host species the father was raised by. This study was a team effort from colleagues at the University of Cambridge and University of Cape Town (Claire Spottiswoode, Wenfei Tong, Gabriel Jamie), at Boston University (Katherine Stryjewski, Jeff DaCosta, Evan Kuras and Michael Sorenson) and in the Choma community in Zambia (Ailsa Green, Silky Hamama, Ian Taylor and Collins Moya).

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