We study the ecological and genetic basis of diversification, using empirical, molecular and comparative methods. This work uses approaches developed in the fields of ecology, behaviour, quantitative genetics and evolution. Most of our study organisms are vertebrates, particularly birds.
Hotspots, biodiversity and extinction
Why have different lineages suffered such very different evolutionary fates, in terms of rates of extinction and cladogenesis? One set of explanations suggests that differences between lineages in macroevolutionary parameters is simply due to chance, with there being no consistent differences in terms of intrinsic biological characteristics between 'winners' and 'losers'. Most of our work suggests that this is not the case, as we have identified a series of robust ecological correlates of variation in both extinction-rate and species-richness. The ongoing challenge is to demonstrate empirically why traits such as ecological specialisation is associated with patterns of extinction and speciation. We are now extending our work to macrecological questions, such as the latitudinal gradient in species richness, the ecological basis of 'biodiversity hotspots', and geographic variation in rates of genetic recombination. This new work combines traditional phylogeny-based comparative methods with new approaches to bioinfomatic mining of genomic databases.
Speciation, sexual signals and colouration
Why do closely-related species often have such very different sexual displays and sexual ornaments? The traditional explanation is that interspecific variation in sexual displays represent 'reproductive character displacement', that is an adaptation to prevent hybridisation with the other species. However, equally plausible explanations include the hypotheses that (i) closely-related species have different signals because they live in subtly different signalling environments, or (ii) racial differences are due to neutral genetic mechanisms such as drift or founder events, or (iii) differences in sexual displays evolve through cultural evolution via sexual imprinting. We test these conflicting hypotheses using a combination of marker-based estimates of genetic covariance, field-based experiments, mate choice trials in the laboratory, quantitative measurement of reflectance spectra, and comparative approaches.We also have related projects on the function of carotenoid-based colouration, fluorescence in parrots, and UV-reflective colouration.
Divergence in ecology and morphology in island-dwelling birds
Island-dwelling races are often very different from their mainland counterparts, in terms of morphology, behaviour and ecology. Insular races of passerine birds, for instance, are often much larger than their mainland counterparts, whereas insular races of non-passerine are generally larger than expected. The traditional explanation for these sorts of shifts are based on selection acting of feeding behaviour due to changes in the level of interspecific competition. Again, however, there are several other explanation including other forms of selection and neutral mechanisms. We are currently testing these competing hypotheses using the island-dwelling birds of the South West Pacific and the North Atlantic, using neutral genetic marker-based methods to estimate quantitative genetic parameters such as heritability and genetic covariance.
Research Student Supervision
Hadfield,DJ, Genetics of coloration in wild populations
Jenkins,MT, Birds, vectors and viruses
Lord,MA, Carotenoids, immunity and coloration in birds
Pigot,MA, Large scale patterns of biodiversity and climate change
Back,MR, Evolutionary ecology of song in birds
Phillimore,DA, Ecological basis of speciation in birds