The sources of diversity shaping adaptive radiation

The plants and animals living on oceanic islands are often unique to them. In general, they form clusters of related species that occupy a range of environments, as each of the species is likely to be adapted to a specific habitat on the respective island. These clusters are often established as a result of a single colonization event by few individuals, sometimes coming from mainland areas thousands of kilometers away. These few individuals will then initiate the entire diversity of forms and functional strategies that will evolve rapidly. However, in order for such explosive diversifications to evolve, considerable amounts of genetic variation are required, which are unlikely to be brought to the island by the small number of ancestor individuals. This project aims to understand the sources of variation that drive diversifications of species on remote islands. It will particularly test a recent hypothesis that biological variation can be triggered as a result of activation of usually dormant selfish genomic components (called transposable elements, or TEs) that in certain conditions can multiply and jump within the genome. The activity of TEs is traditionally expected to be detrimental to the organism, as it can corrupt the genetic information encoded in its DNA. However, TE movements may also produce different variants of genes and their regulators or reshuffle the structure of chromosomes with phenotypic implications. The research will focus on a highly diverse cluster of more than 30 species of persimmons on New Caledonia. This archipelago from the Pacific Ocean has the richest biological diversity per square kilometer in the world. It had a complicated geological history that produced a high diversity of soils which, together with sharp altitudinal and climatic variation, shapes its great variety of habitats. The study group of persimmons is fairly young, but currently occupies all these habitats, except for mangroves. Other persimmons that arrived on New Caledonia at three different time points, have not produced more than a few species that remain ecologically restricted. The project plans to comparatively investigate the evolutionary history and genomic background of the diverse persimmon group against species that did not diversify. Recently published and preliminary data showed that the diverse group is characterized by larger genome sizes and more TEs compared to the other persimmons on New Caledonia. New ecological and physiological data will be collected and combined with cutting-edge genomic investigations to understand what makes the evolution of the diverse group of New Caledonian persimmons special compared to its relatives. The project will investigate in detail the evolutionary context of biological diversifications, and will interrogate the genomic and ecological factors that drive plant adaptation to different soil types, including some extremely challenging for plants.