On the Conservation of the Canarian Laurel Forest: What Do Lichens Have to Say?

The fragmentation and degradation of primary forests are serious threats to the long-term persistence not only of the tree species they comprise, but also of many organisms inhabiting them. The Canarian laurel forest, known as monteverde, is a highly threatened endemic forest of the Macaronesian region. Lichens are considered ideal bioindicators for assessing the effects of human disturbances on ecosystems and anticipating the response of other less sensitive organisms. However, no studies have used them as model organisms to analyze the conservation status of this primary forest in the Macaronesian region. In the present study, we analyzed several variables of the lichen biota of the Canarian laurel forest on the islands with the highest representation within this archipelago: La Gomera, La Palma, and Tenerife. We analyzed the species richness (and its relationship to island size with the real and potential vegetation areas of the laurel forest); the lichen diversity value, the number of shared and exclusive species on each of the islands as well as lichen functional traits as they have become important for evaluating the response of epiphytic lichens to environmental changes. The results indicate that there are signs of a potential extinction debt occurring in the diversity of epiphytic lichens in some areas. Furthermore, it has been observed that, despite the presence of some exclusive species on each island, the overall composition does not differ between them. Considering the functional traits of lichens, there are patterns that can provide information about the unique characteristics of the laurel forest of each of the studied islands.