My research involves the use of both theoretical modelling and experimental work in looking at a wide range of evolutionary and ecological questions. I am mostly interested in how spatial processes (e.g. territoriality, grouping, migrations, etc.) affect the biology of individuals and populations.
My research focuses on understanding the causes, patterns and consequences of animal movement. At the local scale, I am interested in how costs and benefits shape individual behaviour, and how this relates to population level phenomena. Blending theoretical modelling and field observations and experiments, I have shown that male-only care in fish and insects, where males remain in a small territory to look after already obtained offspring while waiting for females to bring them more eggs, is only possible if population density is high enough to guarantee enough encounters with females despite the low mobility of males. I have students working on the role of territoriality in the maintenance of group stability in social dwarf angelfish and of honesty in cleaner wrasses servicing clients on coral reefs. Currently, I mostly work on the solution of conflicts in groups of individuals for which coordination is beneficial. Using sticklebacks as a model system, we have been able to show that personality plays an important role in the emergence of leaders and followers within pairs of foraging individuals. Using continuous time Markov Chain Monte Carlo models, we were able to infer the exact rules that individuals use to respond to each other behaviour, and showed that leadership is the result of social feedback, with strong leaders inpiring faithful followership, and good followers improving the initiative of their leaders.
Selected relevant publications on Individual Movemement
Harcourt, J.L., Ang, T.Z., Sweetman, G., Johnstone, R.A., & Manica, A. (2009) Social feedback and the emergence of leaders and followers. Current Biology 19: 248-252 [PDF] [Suppl. Mat.] [ScienceNOW] [Media]
Harcourt, J.L., Sweetman, G., Johnstone, R.A., & Manica, A. (2009) Personality counts: the effect of boldness on shoal choice in three-spined stickleback. Animal Behaviour 77: 1501-1505 [PDF]
At a broader scale, I am interested in the movement of individuals among populations. The genetic signature left by such movements can be used to reconstruct the history of how population networks have formed (the historical demography of a metapopulation). Humans provide large scale datasets ideal for this sort of questions, and over the last few years we have worked to model the process by which anatomically modern humans migrated out of Africa 50k years ago to colonise the whole world. The rapid spread into new, previously uninhabited lands was characterised by a series of bottlenecks (founder effects) which led to a gradual loss of genetic and phenotypic diversity the further one moves away from the African origin. Reconstructing this process not only tells us something about the origin of a species, but is also fundamental in removing confounding patterns that prevent the meaningful comparison of the effect of selection in different populations. After taking into account the historical demography of humans, we were able to show that genetic diversity at the Major Histocompatibility Complex (MHC, the main genes governing the innate immune response) has been shaped by the number of diseases present in different parts of the world.
Selected relevant publications on Spatial Genetics
Manica A., Amos W., Balloux F., & Hanihara T. (2007) The effect of ancient population bottlenecks on human phenotypic variation. Nature 448: 346-348[PDF][Supplementary Material][ScienceNOW] [Independent] [Guardian][The Economist][Media]
Linz, B., Balloux, F., Moodley, Y., Manica, A., et al. (2007) An African origin for the intimate association between humans and Helicobacter pylori. Nature 445 915-918 [PDF] [Supplementary Material] [BBC Online] [ScienceNOW] [Scientific American] [The Times] [Media]
Prugnolle F., Manica A., Charpentier M., Guegan J.F., Guernier V., & Balloux F. (2005). Worldwide HLA class I diversity: human colonisation history and pathogen-driven selection. Current Biology 15: 1022-1027 [PDF] [Supplemental material] [Nature Reviews Immunology Highlight] [Media]
Ecological communities can be thought as resulting of assemblage rules that are analogous to the forces that shape genetic diversity in populations. Following the formulation of the Unified Neutral Theory of Biodiversity and Biogegraphy, ecologists have become very interested in applying population genetics principles to community ecology. I have been involved in looking at assemblage rules in tropical arthropods and fish. I have also used spatial techniques to look at conservation problems, such as the spread and impact of coral reef fisheries in the Indo-Pacific Ocean.
Selected relevant publications on Spatial Ecology & Conservation
Farnon, M.D., Manica, A., & Foster, W.A. (2009) Stochastic and deterministic processes jointly structure tropical arthropod communities. Ecology Letters 12: 277-284 [PDF]
Tyler, E.H.M., Speight, M.R., Henderson, P., & Manica, A. (2009) Evidence for a depth refuge effect in artisanal coral reef fisheries. Biological Conservation 142: 652-667 [PDF]