Ellen Quinlan, Craig A. Layman , Miles R Silman

The tropical Andes face unprecedented warming and shifting precipitation patterns due to climate change and land-use alteration, challenging the futures of Andean forests. During the Quaternary, many Andean trees responded to climate change through upslope migrations, but while there is evidence of ongoing upslope migrations in many species, they are at rates far below what is need to remain in equilibrium with current climate. Similarly, given the number of generations required for adaptation and the long life-spans of many tropical trees, it is unlikely that most species will be able to adapt fast enough. This synthesis explores the role of migration induced secondary contact and hybridization as potential mechanisms for accelerating the adaptive response Andean forests. Hybridization, historically underappreciated in tropical trees, is increasingly recognized as an important driver of speciation and ecological diversity. It may facilitate gene flow and introgression, providing novel genetic combinations that enhance species resilience to climate change. This process can generate new allelic diversity, allowing species to adapt more rapidly than through mutation alone. However, hybridization can also lead to negative outcomes like genetic swamping and outbreeding depression. Conservation strategies should consider the potential benefits and risks of hybridization in maintaining biodiversity under changing environmental conditions. As habitat fragmentation and deforestation exacerbate the challenges faced by these forests, preserving habitat connectivity will be crucial to facilitate migration and gene flow, potentially aiding the survival of many Andean tree species in the Anthropocene.