The main focus of our research is the study of evolution of biodiversity on islands. We reconstruct how diversity on islands has changed through time using modelling approaches applied to molecular data, and use this to understand how the impact of humans is leading to changes in natural dynamics on islands.
Asteraceae on islands
Asteraceae is the largest plant family in the world, including about 25,000 species, over 1,000 of which are endemic to islands. Why is this group of plants so diverse? Daisies are an ideal group to investigate the dynamics of insular diversification because several islands have multiple colonisations and independent radiations, allowing for sample sizes unrivalled by any other group of plants or vertebrates.
In this project – carried out by PhD student Lizzie Roeble - we are conducting a global analysis of macroecology and macroevolution on island daisies, to identify factors (traits, climate, colonisation history) that drive species diversity in this group. We are also producing and compiling phylogenies representing complete Asteraceae floras from islands worldwide. A particular focus is the archipelago of the Mascarenes (Mauritius, Reunion and Rodrigues) where we are collaborating with local botanists to understand the evolutionary and biogeographical history of the family on these biodiverse but highly threatened islands.
Psiadia dentata (La Réunion)
Islands have experienced exceptionally high rates of extinction after human settlement. For example, one third of Madagascar’s lemurs are now critically endangered, whereas the West Indies have lost half of their mammalian species since humans arrived.
How long would it take for islands to regain the species diversity lost due to humans? How far have we perturbed insular communities from their natural state in the Anthropocene? Focusing on the highly threatened mammalian faunas of Madagascar and the West Indies, we are using phylogenetic methods to measure how much evolutionary history has been lost and how much is currently under threat. While the toll of recent extinction on the species richness on these islands is relatively well understood, we do not know how humans are affecting the natural evolutionary diversity trajectories in Madagascar and the West Indies. We are using the dynamic island biogeography model DAISIE to estimate the trajectory of diversity on these islands based on different past and future extinction scenarios.
Evolution and biogeography of island birds
Birds are the most diverse vertebrate group on islands. They are also perhaps the best studied group on islands, as ornithological work has a long history and there is currently a very active community gathering data on distribution, ecology, traits and life history of insular birds. We use these types of data in combination with new and published molecular phylogenies to understand how, why and when birds colonized and speciated on islands.
Our work on island birds includes recent work on equilibrium dynamics in Galápagos and Macaronesian birds. We also compiled the first global phylogenetic dataset of terrestrial oceanic island birds, which we used for global evolutionary test of MacArthur & Wilson’s theory of island biogeography. We are currently collaborating with ornithologists and NGOs working in the Gulf of Guinea archipelago (Equatorial Guinea and São Tomé and Príncipe) to study the evolutionary history of these highly diverse islands.