Drivers of reproductive isolation in plant radiations

In nature, certain groups of related organisms exhibit varying species richness, one of the three key components of biodiversity. The likelihood of a group undergoing rapid diversification depends on the rate at which reproductive barriers accumulate between emerging species. What remains unclear is whether sudden bursts of species diversification result solely from an increase in ecological opportunities within a specific period and geographic area. Alternatively, additional non-ecological factors may facilitate the greater phenotypic diversity and explain the high diversification rates. These non-ecological factors contributing to higher genetic potential may be associated with different events such as fluctuations in population size, hybridization between distinct species, or phases of accelerated evolution involving reshuffling and/or duplicating parts of the genome, which can all generate novel genetic variation. This project aims to learn more about plant diversification by studying two distant plant genera that each include species-rich and comparatively species-poor groups: the air plants of Tillandsia in the pineapple family, and New Caledonian persimmons (Diospyros). First, we will test if the species-rich groups are accompanied by faster accumulation of reproductive barriers, compared to related species-poor groups. Second, we want to find out the ecological and genetic factors that are responsible for the differential tempo of speciation in these plant groups. Within the framework of this project, the French partners will develop new machine- learning population genomics tools that together with the Austrian team will be used to comparatively study the features of the speciation process between the species-rich and species- poor groups. The project will benefit from and extend an existing large dataset of whole genome sequences and several assembled genomes of both plant groups, recently acquired by the Austrian partners. Our complementary international collaboration will allow us to understand how plant diversity evolves by investigating the environments the respective plants live in and their genomes. By working together, our international team of researchers from three different institutions will combine different strengths to answer central questions in biology.