Jonah Walker

Visiting Scientist

I am an evolutionary biologist researching the processes that facilitate the origin of new species. To do this, I study two species-rich biological groups in the field and in the lab: Australian peacock spiders and South American ithomiini butterflies. I combine genomic sequencing with whole-spectrum photography and behavioural experiments in order to gain a more holistic view of evolution. 

In a little under 4 billion years, life has evolved from one primordial species into hundreds of millions of species. The most striking feature of the tree of life is the uneven distribution of species richness and phenotypic diversity. My work seeks to explain why some biological lineages have become so brilliantly diverse while others have remained comparatively depauperate.
Working between the Tree of Life Programme at the Sanger Institute and the Department of Zoology at the University of Cambridge, I am addressing two long-standing questions at the intersection of speciation genomics and sensory ecology. First, what role does hybridisation and genomic admixture play in fuelling bouts of rapid speciation and signal diversification? Second, how do signals evolve during the course of a radiation and what role do they play in facilitating speciation? I address these two questions using two colourful study systems: the peacock spiders of Australia and the ithomiini butterflies of South America.
I firmly believe that biology benefits from an interdisciplinary and collaborative approach. My research is grounded in field-based observation and I combine this with genomic sequencing, multispectral imaging, and behavioural experiments in the lab.
My research is kindly funded by the Wellcome Sanger Institute and by the Herchel Smith Trust at the University of Cambridge. I am supervised by Joana Meier and Chris Jiggins.

1) Peacock spiders

The peacock spiders of Australia represent a series of recent and rapid radiations. The genus Maratus comprises around 100 species and its males are infamous for the remarkable visual and vibrational dances that they perform to attract females. This extreme sexual dimorphism, together with a lack of observable ecological differentiation between species, suggests the radiation is driven primarily by sexual selection. Unlike ecological radiations, sexual radiations are severely understudied at the genomic and phenotypic level. For this project, we are working as part of a collaboration spanning Australia, the UK, the US, and Germany.

2) Ithomiini butterflies 

The speciose butterfly genera Mechanitis and Melinaea represent recent, rapid radiations driven by ecological divergence. Their stunning wing patterns, which belong to aposematic Müllerian mimicry rings, have diverged substantially between and within species. The exceptional degree of sympatry of species, subspecies, and morphs in these genera, together with evidence of hybridisation between lineages, makes them prime radiations to address my questions. For this project, we are working as part of a collaboration spanning Ecuador, Colombia, French Guiana, Brazil, Panama, the UK, and France.

Additional projects

I’ve been very fortunate to work on a wide range of evolutionary projects around the globe. With Claire Spottiswoode, I am also studying the effect of interactions between brood parasitism and climate on egg signature evolution in Zambian Prinia warblers. And with Andrew Tanentzap, I am investigating how predictable the evolutionary responses of Daphnia populations are to invasive predator introduction in Canadian lakes. I’ve also worked on stickleback collective behaviour, Heliconius signal evolution in Panama, and Podarcis lizard hybridisation in Switzerland.

My timeline