Around the world, 35 areas qualify as biodiversity hotspots. These are places with at least 1,500 endemic vascular plants and 30% or less of their original natural vegetation. Together, they represent just 2.3% of Earth’s land surface, but they support more than half of the world’s endemic plant species. Our research focus is on developing tools for quantifying the importance of particular sites in these hotspots, and developing ex situ conservation plant collections of species derived from them. Our research collectively focuses on the Mediterranean Basin, Ethiopian and Japanese floristic regions, where we are collaborating with local botanists on each of these floras. We are building an extensive collection of critically endangered and red-listed species from Japan at the Garden and Arboretum in conjunction with this research.