We are interested in the ecological causes of, and genetic responses to, natural selection. Given the close links between the fields of ecology and evolution, it is surprising how little we understand about the environmental factors and ecological interactions that drive natural selection (and therefore the great majority of evolution). An improved understanding of these things would greatly inform our comprehension of the natural world, and could help us to deal with the effects of global change. We are currently working on two main projects:
"Multivariate evolution in replicated adaptive radiations: pattern, process and the role of the environment." Funded by a NERC standard grant
Adaptive radiations have occupied a central role in thinking about pattern and process in the evolution of biodiversity. In analyses of phenotypic biodiversity, evolutionary biologists have relied on two conceptual tools: the genetic variance covariance (G) matrix and different forms of the selection surface. The former quantifies genetic correlations between phenotypic traits, while the latter represents the relationship between phenotype and fitness. Together these two concepts have helped to reveal a number of important principles: (i) genetic variation is plentiful, at least for individual traits, (ii) the majority of phenotypic diversification results from selection rather than drift, (iii) evolution can happen rapidly, yet (iv) evolutionary stasis is common, and (v) when evolution does occur, multiple phenotypic traits often evolve in concert. For example, often in adaptive radiations, trait values evolve only so much and then stabilise, and trait mean values are correlated across closely related taxa. These principles are well established, but our understanding of their causes is less than it should be. In this project we will use two recent conceptual advances to progress our understanding: (A) MacColl and others have emphasised the rewards to be gained by connecting evolution more explicitly to the environment. The evolution of biodiversity is shaped by the environment, but our comprehension of this relationship is surprisingly poor. (B) Phenotype, genotype and environment all have complex structures. Recent multivariate approaches have stressed the insights into evolution that may be gained by explicitly investigating these, where traditional univariate analyses have stalled. Recognising the importance of (A) and (B) will allow significant progess in our understanding of phenotypic biodiversity. Adaptive radiations of three-spined sticklebacks, with their abundant variation in both phenotypes and environment, provide an outstanding study system in which to take advantage of these developments. Our aim is to understand the role of the multivariate environment in the evolution of biodiversity by analysing patterns of multivariate phenotypic divergence in replicate adaptive radiations of sticklebacks, using cutting edge statistical techniques. We will collaborate with Paul Hohenlohe, who is at the forefront of developing these techniques, and an international network of stickleback biologists (Dolph Schluter, Mike Bell, Steve Vamosi, Skúli Skúlason and Bjarni Kristjánsson). Our objectives comprise three related fundamental evolutionary questions:
(i) How do the environment and genetic constraints contribute to phenotypic divergence? Evolution has resulted in abundant diversity in the natural world, but the extent of this divergence within related groups of organisms is circumscribed. To what extent do these limits, on the kind of organisms that evolve, result from genetic constraints and biases versus patterns in the environments to which the organisms are exposed?
(ii) Can repeatability (parallelism) in evolution be explained by the environment? Within the greater divergence, organisms have often apparently converged on similar phenotypic solutions, suggesting that evolutionary outcomes are to some extent repeatable. Is this the result of genetic biases or the environment? If the latter, do similar environmental combinations always result in essentially the same organism, or are there different evolutionary solutions to similar environmental problems?
(iii) Is phenotypic novelty associated with unusual environmental circumstances? Although related organisms in different places often converge on repeated evolutionary solutions, evolution also occasionally comes up with solutions that are different from the general pattern, through organisms developing, or losing, some distinguishing feature or combination of features. Is such evolutionary novelty the result of particularly unusual environments?
"Environmental and demographic determinants of natural selection". An international working group funded by the National Evolutionary Synthesis Centre, USA
Understanding how organisms will adapt to changing environments is one of the main challenges facing biology, and evolutionary biologists are uniquely positioned to make important contributions in this area. However, evolutionary biologists have only a poor understanding of how environmental change will affect evolution in natural populations. A better description of the relationship between the environment and natural selection is essential to attaining this understanding, because natural selection underpins adaptive evolution, and its strength and form is influenced by environmental variation. In this Working Group we will quantify two important ways in which the environment may affect selection: (a) how it moulds the distribution of traits that are exposed to selection, through its effect on their expression and development and (b) how it shapes the relationship between phenotype and fitness. We will use recently developed integral projection models and existing long-term and spatially replicated datasets to achieve this synthesis. Our approach will improve our ability to predict the dynamics of adaptation to environmental change, and will increase our fundamental understanding of evolution. Collaborators: Stephanie Carlson (Berkeley), Tim Coulson (Oxford), Adam Siepielski (San Diego). Other participants include Mat Buoro (Berkeley), Chris Caruso (Guelph), Sonya Clegg (Griffith), Clinton Francis (NESCent), Joe Hereford, Joel Kingsolver (North Carolina), Loeske Kruuk (Edinburgh), Ryan Martin (NIMBios), Michael Morrissey (St Andrews), Ben Sheldon (Oxford), Nina Sletvold (Uppsala), Erik Svensson (Lund) and Mike Wade (Indiana).
Parasites are ubiquitous in wild populations, and the immune and other responses to infection of their hosts are highly variable within and among populations. However, the ecological and evolutionary causes and consequences of variation in infection, and host responses to it, are poorly understood. A better understanding of these would improve our comprehension of a major set of factors that govern biodiversity, as well as possibly assisting in the control and treatment of animal, and even human, disease.
Using three-spined sticklebacks as a model system, we have previously found that levels of infection with parasites can differ greatly between populations, and that these differences can remain consistent over many years. These differences in infection rates are associated with differences in resistance to some parasites. Populations experiencing high levels of infection tend to exhibit higher levels of resistance to those infections. When animals attempt to disperse between populations with different kinds of parasites, differences in resistance can have significant effects on e.g. growth, which may reduce the chances of successful dispersal.
Aliya El Nagar has recently finished a PhD examining the genetic basis of variation in parasite resistance using quantitative (e.g. line-cross analysis) and molecular (e.g. RNASeq) genetic techniques. Aliya also looked at whether signatures of genetic divergence among populations can be accounted for by variation in the parasites that they experience.
Shaun Robertson (co-supervised by Prof Jan Bradley and Dr Sara Goodacre) is following up the work of Aliya, looking in greater detail at genetic variation in responses to infection in sticklebacks, using quantitative PCR and comparative genomics. He is using experiments to test the ecological and evolutionary significance of variations in host responses.
Muayad Mahmud (co-supervised by Prof Jan Bradley) is looking at variation in virulence between different populations of parasites, the ecological correlates of this and the consequences for host responses to infection. He is using the interaction between sticklebacks and parasites of the genus Gyrodactylus as a model system.
Becca Young is doing an MRes in which she is using data collected from wild fish from many populations over several years to examine interactions between parasites, and whether these have important effects on host fitness.
Jim Whiting has recently started a PhD project on the evolutionary consequences of genetic adaptation to parasites.
Most aspects of the evolution of organisms are affected by the environment in which they live, and the ecology they experience. Recently researchers have begun to realise that the evolution of organisms can also affect the ecology of the environments in which they live, so-called 'eco-evolutionary dynamics'
Abdul Rahman is examining the effect of environmental variation on life-history evolution in three-spined sticklebacks. In particular he is using otolith based methods to quantify probabilistic reaction norms, and how these are related to ecology, growth and reproductive investment.
Talib Chitheer is quantifying plankton community and fish phenotypic variation in lochs on North Uist, Scotland to test ideas about eco-evolutionary dynamics.
Laura Armstrong (co-supervised by Dr Suzanne McGowan, School of Geography) will be using paleaolimnological techniques, detailed topographical surveying and molecular genetics to test hypothese about the role of sea-level change in driving speciation in sticklebacks.
Many of the species and ecosystems studied by evolutionary biologists and ecologists are under threat from diverse sources. Careful scientific study of species and ecosystems can help to reveal the full nature of such problems, and may help to suggest solutions.
Chris Heward, who is based mainly at the Game & Wildlife Conservation Trust (Supervisor Dr Andrew Hoodless), is using large-scale population and habitat surveys to try to understand the effects of landscape influences, wood-scale processes and climate change on the Eurasian woodcock, a declining woodland specialist bird species.
Group members have previously worked on projects including:
(1) The ecology of the British willow tit (Poecile montanus kleinschmidti), an endemic subspecies, and one of the UK's most rapidly declining bird species.
(2) The exploitation of wildlife in the Ugalla ecosystem in Western Tanzania.