Our research
150 years on from the ‘Origin’ and we have yet to unravel how ecological speciation works, and how it leads to spectacular examples of adaptive radiation. Adaptive radiation has two components: adaptation to differing ecological niches and the production of new, reproductively isolated, species. The aim of this project is to make breakthroughs in understanding ecological speciation by the study of geographically parallel adaptive radiations in mycalesine butterflies (Nymphalidae: Satyrinae: Mycalesina) that have yielded some 270 extant species in the Old World tropics. All major regions of distributions of the group - Madagascar, Africa, the Indian subcontinent, Indo-China, the larger islands of South-East Asia (notably Sulawesi), New Guinea and the Solomon Islands - are each represented by a species-rich mycalesine fauna, with the Indo-Australian, Afrotropical and Madagascan regions having roughly equal numbers of species. These butterflies occupy both open and forested habitats and are generally poor dispersals with high endemicity.
Our current research seeks to build on twenty years of work on one of these species - Bicyclus anynana – which has identified key sets of traits involved in adaptation and in speciation. Our evo-devo work on the wing eyespots of this species has also begun to compare patterns of flexibility in eyespot morphospace, as observed in laboratory evolution, with the pattern of occupancy in the same morphospace for extant mycalesine species. More empirical studies of such systems are needed because of the surprisingly small number of adaptive radiations that have been extensively examined from many different perspectives (including in insects). It is not fully understood either how exactly radiation occurs or how exactly selection leads to speciation. Somehow the processes of natural selection and speciation yield suites of traits which differ among reproductively isolated species inhabiting different ecological niches. This project provides a unique opportunity, outside a few select clades in birds and lizards, to resolve such issues by fully integrating several lines of evidence and methodologies. The approach here will be to make intensive studies of patterns of diversity and disparity in morphospace for several sets of key traits: 1) wing patterns, including seasonal polyphenism, 2) larval host plant choice especially with respect to C3 and C4 photosynthesis, and 3) male secondary sexual traits, sex pheromones and courtship behaviour. We will collect phenotypic, genetic, developmental, and ecological data. Comprehensive mapping of traits in morphospace and on to phylogenies will enable effects of contingency and constraint to be analysed. Application of phylogenetic comparative methods to the relationships of all traits among all species will make inferences about the biological mechanisms that have driven diversification and speciation, e.g. genotype-phenotype mapping, genetic drift, ecological selection, and sexual selection. The combination of surveys of occupancy in morphospace for independent radiations, the use of comparative methods, and microevolutionary studies using laboratory models will provide a unique comprehensive view of a series of insect radiations. Our analyses will distinguish among alternative patterns of adaptive radiations, test predictions from models, and move us forward in identifying the drivers of observed patterns of diversity and disparity at the levels of adaptation to ecological niches and the evolution of reproductive isolation. Finally, we will be able to compare these insect radiations with the classic studies of different groups of vertebrates.