Cambio climático, nicho térmico y conservación de la biodiversidad subterránea

Résumé

Predicting the effects of climate change and designing effective biodiversity conservation strategies are two major challenges for the scientific community. The subterranean environment is one of the few ecosystems where, due to its constant environmental conditions, it is possible to obtain accurate predictions of the species response to climate change. Moreover, it is directly connected to the surface and consequently, affected by several human threats that have triggered alteration processes leading to the loss of subterranean biodiversity. It is therefore urgent to assess how far the current networks of protected areas are effective for the protection of subterranean biodiversity. The main objectives of this thesis are: i) to predict the vulnerability of subterranean biodiversity to climate change, combining information on the thermal physiology, ecology and evolutionary relationships of different subterranean species from several taxonomic groups and study areas, and ii) to assess the effectiveness of protected area networks in conserving subterranean biodiversity. The thesis is structured in 4 specific objectives: In the objective 1, the physiological upper thermal limit of a subterranean pseudoscorpion was estimated following two different approaches: i) from climatic data in its current localities; and ii) from physiological experiments. The results show that, according to the first method, the risk of local extinction could be high for at least half of the populations of the species studied. This alarming message can be mitigated by considering the results of the physiological experiments, which shows that complementary approaches to estimating thermal tolerance provide more accurate predictions of the species' ability to cope with climate change. In the objective 2, the plasticity of the upper thermal limit of 3 beetles with different degrees of subterranean specialization, exposed to different acclimation treatments, was determined. The most specialized species to the deep subterranean environment lacked acclimation capacity. However, the least specialized species was able to increase the upper thermal limits after a few days of exposure to higher temperature. In the objective 3, the upper thermal limit of 16 subterranean beetles was estimated, their degree of specialization to the subterranean environment was characterized using morphological and ecological traits, and habitat temperature data were obtained for each species. The results show that highly specialized species have lower heat tolerance than less specialized ones, regardless of the mean temperature of their habitat. Therefore, the vulnerability of subterranean species to climate change will greatly depend on their degree of specialization to the deep subterranean environment. In the objective 4, a distribution database of subterranean species of two taxonomic groups (beetles and spiders) in two subterranean biodiversity hotspots (the Pyrenees and the Alps) was compiled in order to i) identify priority areas for their conservation, as well as ii) to assess the extent to which they are covered by surface protected areas. More than 70 and 90% of the priority areas for subterranean biodiversity conservation (and 40 and 22% of the species) are not effectively covered by protected areas in the Pyrenees and the Alps, respectively. In addition, forty-nine more hydrographic basins were identified in the Pyrenees and 22 in the Alps that would need to be protected to cover all species that currently are outside protected areas. These results highlight the urgent need to develop a coherent plan for the conservation of subterranean biodiversity.