PhD thesis: On the dynamics of biodiversity on insular systems (2024)

Understanding how biodiversity on earth changes over time requires reconstructing species' history. This is difficult due to the complexity of ecosystems and the movement of species between regions. Islands enable us to study biodiversity within well-defined borders, with simpler ecosystems to reconstruct. The principal way we can reconstruct biodiversity through time, when fossil data is not available, is by using genetic data to produce a "tree of life" informing when new species originate (speciation) and their relationships. Using this information we can study life on islands and make insights generalisable to the planet's biodiversity. In this PhD research I, along with collaborators, developed mathematical models to investigate ecosystem assembly and diversification of island species. We show that for the amphibians, birds, mammals and reptiles of Madagascar there is very little evidence that the species currently on the island descended from species that were already present on Madagascar when it fragmented from other landmasses, and that over time speciation and extinction differ between the groups. In another study, again developing a new mathematical model, we show that there is some evidence that formation of new species and extinction varies within bird communities on archipelagos, in particular finding that some archipelagos have a single exceptional group of birds that diversifies differently from the community (e.g. Darwins's finches on the Galápagos). This PhD thesis involved developing open-source software, including island biogeography data science tools, and testing the performance of mathematical models to ensure that our conclusions on biodiversity dynamics on islands are valid.