The history of life has shaped the life histories of species on our planet. What are the determining factors that have produced the multitude of forms and strategies observed? From simple linear growth trajectories, to complex larval and adult life forms, the life history variations of species reflect the different selective forces that current species experience and that their ancestors were subjected to. Researchers have looked for the adaptive bases of variations in life history traits, investigating patterns of life history strategies across the tree of life and across the different habitats of these species. This search has revealed fascinating evolutionary patterns across phyla. Within certain groups, life history traits exhibit conservatism among major lineages (e.g., oviparity in birds), whereas in other groups, traits have often been independently acquired, showing patterns of convergence and parallelism (e.g., viviparity in reptiles, and ovo-viviparity in amphibians). Why do we see major life history similarities, as well as differences, among species?

Studies of African amphibians have revealed new insights into the remarkable breeding strategies of species from Africa. Direct development for instance is thought to have evolved at least 8 times in Africa compared to as few as about 20 times worldwide. The independent evolution of direct development in African amphibians is even more striking when the low species diversity of Africa is considered. The high diversity of African amphibian life histories and relatively low species diversity in Africa suggests something unique either about the continent of Africa (the environment and its history) or the African radiations. Our aim is to investigate the adaptive significance of the terrestrialization of development in African amphibians, a multiply acquired life history strategy evident in independent clades of amphibians. We will test specific temporal and spatial hypotheses on the environmental correlates of terrestrialization. Principally, we will test the central hypothesis that the terrestrialization of African amphibian life histories is a key adaptation that has allowed species to diversify in mountain and forest habitats.

In this proposal our team will seek to address fundamental questions on how life history strategies in African amphibians have developed over time and space. We address this question by looking at the biogeographical correlates that might explain the evolution of the diversity of developmental terrestrialization in African amphibians. This will be investigated through state of the art methods and novel approaches that combine ecological and evolutionary approaches. Based on ecological data from IUCN databases and data assembled by our group we will conduct statistical spatial analyses on three independent radiations of African amphibians (Bufonids, Afrobatrachia and Caecilians). We will look for significant correlations between life history strategy traits and environmental parameters (e.g. climate and habitat). Complementing this we will conduct phylogenetic analyses on the same species and reconstruct evolutionary trees (timetrees). Combining these data, we will reconstruct life history characters on evolutionary trees, test synchrony of shifts in life history strategies among clades, and compare shifts in diversification rates and climatic niches among species and clades associated to terrestrialization. Understanding the overall patterns by which life histories have changed through evolutionary time will elucidate potential mechanisms of how, and under what circumstances key innovations, such as terrestrialization, have developed spatially and temporally.