Our Work

Our research in Zambia addresses the general theme of how interactions between species shape evolution and generate biological diversity. We are all passionate naturalists and our work is all inspired by natural history and field observations, and depends heavily on experiments in the field. With the help of interdisciplinary collaborations, we also integrate fieldwork with techniques drawn from other fields such as evolutionary genetics, sensory biology, physiology, and applied mathematics.

We primarily study brood-parasitic birds, which are a wonderful system for researching coevolution in the wild. This is because they are locked into coevolutionary interactions with their hosts, demanding continual adaptation and counter-adaptation in both parties. They are also very tractable to field experiments. Africa is an excellent place to study brood parasites as it contains the greatest diversity of brood parasites in the world. These interactions between tropical species are often oldest and therefore most revealing of general evolutionary processes.

Much of our research addresses two general themes:

Research - egg circle

1. How do signals of identity evolve?

We are interested in understanding how coevolution shapes sophisticated signals of identity. Our work has shown that parasitism by cuckoos and cuckoo finches has driven hosts to evolve visual ‘signatures’ of identity on their eggs, made up of different combinations of colours, spots and scribbles. The astonishing beauty and diversity of egg signatures is thus the outcome of a coevolutionary arms race between signatures and forgeries: hosts are driven to escape mimicry by evolving new egg types, but are constantly pursued by the parasite. A current research focus is to ask what are the design hallmarks (both phenotypic and genetic) of a perfect signature, and reciprocally, those of a perfect forgery.

Research - egg pairs

2. How is specialisation to different coevolutionary partners maintained?

Reciprocally, coevolution has shaped ancient genetic specialisation in parasites. Our work In collaboration with Prof Michael Sorenson at Boston University, has shown that ancient host-specific genetic lineages exist within certain parasitic species. These lineages have been shaped by coevolution with hosts and allow the integrity of intricate host-specific adaptations to be preserved. For example, in greater honeyguides, we have found that different strains of females within a single parasite species transmit the genes for egg mimicry from mother to daughter via the W chromosome (that in birds is carried only by females), and have thus remained perfectly faithful to different host species for several million years. Our research has also highlighted how phenotypically plastic processes such as imprinting can be associated with highly specialised chick mimicry in parasitic finches, by facilitating speciation.

More generally, we are intrigued by how the mechanistic basis of coevolutionary adaptations and counter-adaptations might shape the trajectory of evolutionary arms races. Together with our collaborators, we are currently further exploring how cognition, genetics, biophysics, biochemistry and physiology might promote or constrain coevolutionary diversification.

Zambia is a particularly wonderful place to address these questions in part because of its remarkable diversity of brood-parasitic birds: 31 species occur, representing four of the seven groups in which brood parasitism has independently evolved in birds. Our work focusses particularly on eight species from three of these independently evolved groups: four species of parasitic finch from the genera Anomalospiza and Vidua (Viduidae), two species of honeyguides (Indicatoridae), and two species of Cuculinae cuckoos.

The Study Systems pages on this website give an overview of the natural history of each of these bird families, and summarise some of our past findings.

On the Study Systems pages,  you will also find information on two other research topics we have investigated at our study site in Zambia, with links to the theme of species interactions: first, how does the winter ecology of migratory birds allow them to exploit a radically different biotic and abiotic environment on their African non-breeding grounds? Second, how does predator vision shape the evolution of nest camouflage in ground-nesting birds?

All these research themes also benefit from cooperation with other Zambian biologists, and we work closely with colleagues at Copperbelt University, the Livingstone Museum and (forthcoming in 2021) the Choma Museum on collaborative research, capacity-building, and public outreach.

Our work also depends crucially on the field skills and hospitality of the local community where we work, in the Choma District of southern Zambia (see The Team and Thanks).

Please also visit our sister research project in Mozambique, which seeks to understand the other side of the life of one of our brood-parasitic study species, the Greater Honeyguide, as a cooperative partner of our own species: www.africanhoneyguides.com.

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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