Land-use change presents major threats to biodiversity, with impacts often outpacing those from climate change. Impacts of land-use change can often be delayed or cryptic but can nonetheless have severe consequences for tree species, leading to higher extinction risks and lowering the potential for adaptation to a changing environment. Land use is a dynamic force, while the expansion of agricultural land is still the major driver of forest cover loss in tropical regions, secondary forests have been re-establishing on former agricultural lands and forest clearings. These newly regenerated forests have enormous potential to support biodiversity and provide essential ecosystem services. The Caribbean archipelago of the West Indies comprising the Greater and Lesser Antilles, and the Bahamas is one of the world's 34 biodiversity hotspots, hosting over 13,000 plant species. These islands harbour high levels of biological diversity and share a long and disruptive colonial history that has shaped and transformed the ecosystems through logging, large-scale plantation, and permanent dwellings. Today most of the forests on these islands underwent a process of natural regeneration with the formation of secondary forests. The island of Puerto Rico exemplifies this phenomenon. In the early 1900’s, forest cover on the island had been reduced to ca. 6% due to land clearing for agriculture. A variety of political and socio-economic changes during the mid-1900’s led to the widespread abandonment of agricultural land and the subsequent natural regeneration of forests. Currently, forest cover on the island is estimated at ca. 55%. This dramatic shift in forest cover represents a valuable opportunity to study land-use dynamics that are becoming increasingly common in other tropical regions. The overarching aim of this project is to better understand how land-use dynamics have affected the current geographic distributions, population sizes, and genetic diversity of tropical trees on the island of Puerto Rico. The specific objectives are: 1. To describe and compare genetic diversity across Puerto Rico for a set of focal species with diverse life-history traits. 2. Investigate the impact of change in land use on change in genetic diversity.