Population responses to dramatic environmental pressure can involve correspondingly dramatic adaptation characterised by rapid change. The conditions favouring such major episodes of adaptive evolution are an enduring interest: understanding the underlying genetic, behavioural, and environmental factors is particularly important for predicting how organisms might adapt to the dramatic environmental changes human beings impose upon them through climate change, anthropogenic disturbance, or the introduction of non-native species.
A current flashpoint for debate concerns the role that phenotypic plasticity plays in adaptive evolution. Plasticity could shield populations from the action of selection, slowing adaptation, but a counter-argument is that plasticity allows new genetic variants to invade the genome under selection while protecting against associated fitness costs. When plasticity arises from the social environment, further complexity may be added to the evolutionary process. Critically evaluating recent models and verbal arguments about the role of social plasticity in adaptation is thus a major priority, and this project will tackle the issue using a rapidly evolving species of Hawaiian crickets.
In Hawaiian populations of the field cricket Teleogryllus oceanicus, some males recently lost the ability to sing due to Mendelian mutations that erase-sound producing structures on their wings. These silenced ‘flatwing’ males are protected from aerial death attacks by an acoustically-orienting parasitoid (Ormia ochracea), but at the cost of losing their normal means for attracting mates. The flatwing morph has spread rapidly in multiple populations, and a growing body of research suggests that plasticity to the social environment has capacitated this rapid evolution. Intriguingly, plasticity to the social environment may be co-evolving with the adaptive mutation itself.
This project will join fieldwork, behavioural experiments, and genetics to test the role of phenotypic plasticity in adaptive evolution.
I. Measure how abiotic and social environments vary in replicate field populations of crickets.
Survey replicate Hawaiian populations of T. oceanicus in which the silent flatwing morph has invaded and spread. The student will use field data to test whether and how environmental (e.g. ecological, habitat, weather) and social (e.g. demographic factors such as density and competition risk) environments are related in nature, and test factors that could enhance or impede the invasion success of silent males.
II. Test how plasticity to abiotic environments (nutritional availability) interacts with plasticity to social environments (the perception of conspecifics).
Perhaps because calling is energetically expensive, crickets show impressive levels of plasticity in calling behaviour depending on their nutritional budget and their intake of particular macro- and micronutrients. However, the extent to which the resource-dependence of sexual signalling affects social plasticity in calling remains unclear. Using a quantitative genetic framework, the student will test how plasticity to the nutritional environment interacts with plasticity to the social environment. This experiment will measure indirect genetic effects (IGEs) arising from the social environment of crickets and enable the student to investigate what abiotic factors might cause the evolutionary consequences of IGEs to vary. The experiment will use a split-family experimental design to allow estimation of quantitative genetic parameters for plasticity and identification of variably plastic genotypes. By joining the results of this project with data from wild populations, the student will evaluate the hypothesis that IGEs arising from social plasticity account for faster evolutionary adaptation.
III. Definitively test whether socially-mediated phenotypic plasticity in crickets is adaptive or non-adaptive.
A major topical debate is whether plasticity’s role in evolution is stronger when it is adaptive or non-adaptive. Is plasticity just an unavoidable developmental consequence of varying environments, or is it an adaptation that has been shaped by selection? This component of the project will manipulate the social environments of crickets and then measure fitness in environments which either match or mismatch their prior experience. The student will implement this powerful design using competitive fitness assays and genotypes identified from the prior experiment varying in their tendency to exhibit plasticity (the experiment does not depend on such lines, however, and if none are identified the project will proceed by using laboratory strains established from different island populations). The match/mismatch experimental design will be complemented with cutting-edge behavioural assays to link fitness variation with any behavioural plasticity. A significant benefit of this project is that the student will undertake a secondment to Bussière’s laboratory at the University of Stirling to take advantage of a state-of-the-art Electronic Acoustic Recorder to measure male calling effort in normal-wing crickets.
Funding up to 3.5 years includes:
A tax-free maintenance grant set at the UK Research Council’s national rate;
Full payment of tuition fees at the Home/EU rate;
Access to extensive research support funding; &
Support for an external placement of up to six months.
Applications from Home/European Union candidates only. International candidates are not eligible to be considered and where an candidate from another EU country has not been resident in the UK for 3 years or more prior to the commencement of their studies with IAPETUS2, they will only be eligible for a fees-only studentship.
Pascoal S, Liu X, Fang Y, Paterson S, Ritchie MG, Rockliffe N, Zuk M, Bailey NW (2018) Increased socially mediated plasticity in gene expression accompanies rapid adaptive evolution. Ecology Letters. 21:546-556.
Bailey NW, Marie-Orleach L, Moore AJ (2018) Indirect genetic effects in behavioral ecology: does behavior play a special role in evolution? Behavioral Ecology. 29:1-11.
Pascoal S, Cezard T, Eik-Nes A, Gharbi K, Majewska J, Payne E, Ritchie MG, Zuk M, Bailey NW (2014) Rapid convergent evolution in wild crickets. Current Biology. 24:1369-1374.
Bailey NW, Zuk M (2012) Socially flexible female choice differs among populations of the Pacific field cricket: geographical variation in the interaction coefficient psi (ψ). Proceedings of the Royal Society of London, B. rspb20120631.
Bailey NW, Moore AJ (2018) Evolutionary consequences of social isolation. Trends in Ecology and Evolution. 33:595-607.
Houslay TM, Houslay KF, Rapkin J, Hunt J, Bussière LF (2017) Mating opportunities and energetic constraints drive variation in age-dependent sexual signalling. Functional Ecology. 31:728-741.
Houslay TM, Hunt J, Tinsley MC, Bussière LF (2015) Sex differences in the effects of juvenile and adult diet on age-dependent reproductive effort. Journal of Evolutionary Biology. 28:1067-1079.
Buser CC, Ward PI, Bussière LF (2014) Adaptive maternal plasticity in response to perceptions of larval competition. Functional Ecology. 28:669-681.
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FTE Category A staff submitted: 50.45
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