Climate warming and introduced herbivores disrupt alpine plant community of an oceanic island (Tenerife, Canary Islands)

Invasive alien species and climate change are two of the main current threats to conservation of biodiversity worldwide. Their effects have been extensively studied individually, but we know less about their combined effect. This study analyzes the population changes in the plant community of the high mountain legume shrub habitat of Tenerife over 10 years (between 2009 and 2018), using alien herbivore exclusion plots distributed over two sectors with different patterns of climate. Our outcomes show contrasting effects of herbivory and climate in plant communities, with significant shifts in community composition. The dominant species, Teide broom (Spartocytisus supranubius), is negatively affected by both climate and alien herbivores, leading to a regression of its abundance. In contrast, a formerly rare species,Pterocephalus lasiospermus, is benefiting from warmer temperatures and from herbivore presence owing to its low palatability. Simultaneously, some thermal native species from the neighboring pine forest are invading the alpine ecosystem. We conclude that the alpine habitat is changing very quickly and differently according to whether it is in warmer or colder sectors of the summit of Tenerife. This work reveals the need to simultaneously consider multiple drivers to understand the response of mountain ecosystems to global change.