Diversity of epiphytic communities (lichens and bryophytes) in tropical forests of Southern Ecuador

Abstract

In recent decades, deforestation and habitat fragmentation have been the primary causes of biodiversity loss. In the context of the southern Ecuadorian tropical forests, these pressures have intensified due to human activities, leading to the rapid disappearance of primary tropical forests. These forests are being replaced by secondary forests and plantations. Within these ecosystems, the diversity of non-vascular epiphytic organisms, composed of lichens and bryophytes, plays a crucial role in their functioning. These epiphytic species are involved in nutrient and water cycles, as well as serving as refuges and food sources for various invertebrate groups. However, studies evaluating the impact of deforestation and habitat fragmentation on lichen and bryophyte epiphyte communities and their functional traits have primarily focused on boreal forests or Mediterranean temperate forests, with limited knowledge in tropical ecosystems. Therefore, the overall objective of this doctoral thesis is to understand the biodiversity associated with these tropical forests, which are currently in decline, and to assess the effects of deforestation and fragmentation on epiphytic lichen and bryophyte communities associated with these tropical forests. To address this objective, the following studies were conducted: 1. Floristic study in the Tepuis of the upper Nangaritza. A study based on the identification of epiphytic lichens was carried out in this highly diverse area of the Tropical Andes, currently threatened by agricultural and mining expansion. 2. Assessment of biodiversity associated with fragments of secondary forests. Three categories of secondary forests were defined: mixed secondary forest, monospecific secondary forest, and plantations. In each of these secondary forests, changes in taxonomic and functional diversity of epiphytic communities (lichens and bryophytes) were analyzed. Additionally, factors such as altitude, forest type, and tree diameter that could modulate the diversity of these communities were identified. 3. Evaluation of fragmentation impact in tropical secondary forests. Different forest fragments were selected to analyze the taxonomic and functional richness and cover of epiphytic lichen communities along an edge-interior gradient. The results indicate the high diversity associated to Tepuyes and the lack of knowledge about epiphytic lichens in these areas. Moreover, forest type and edge effects associated with fragmentation have an impact on the diversity patterns of epiphytic communities. Species turnover is observed, related to alterations in forest structure. These alterations affect microclimatic conditions, such as increased light levels, temperature, wind penetration, and decreased relative air humidity. Certain traits, such as crustose growth form and species with green algae as photobionts, were dominant across all analyzed forests, reflecting species adaptability to disturbances. In conclusion, these findings highlight the importance of research in still unexplored areas to increase the knowledge of epiphytic biodiversity in tropical areas. In addition, these studies conducted in secondary and fragmented forests underscore the importance of microclimatic conditions along the edge-interior gradient for epiphytic communities. Furthermore, incorporating functional traits into these studies is essential, as they modulate the richness and composition of epiphytic communities across environmental gradients.