Susana Pallarés

Museo Nacional de Ciencias Naturales Madrid · Biogeografía y Cambio Global

Facing the threat of global warming requires accurate predictions of how species will respond to future environmental changes. Despite the fact that high-altitude systems will experience some of the fastest rates of warming on the planet, projections of the impacts of climate change on alpine freshwater biota are still scarce, especially for Mediterranean mountain ranges. Sierra Nevada mountains (south Spain) harbour a unique representation of the Iberian mountain freshwater ecosystems, including alpine lagoons and ponds. The project AlpineDiving (Vulnerability and adaptation to climate change in freshwater endemics of Sierra Nevada), aims to study the vulnerability to ongoing global warming of high-mountain aquatic insects by integrating physiological-based metrics of sensitivity with future climatic exposure. Notably, it focuses on two threatened water beetles (Agabus nevadensis and Hydroporus sabaudus sierranevadensis; family Dytiscidae) endemic to alpine lagoons of Sierra Nevada national park in order to: (1) update the information about the distribution of these taxa and assess the status of their populations; (2) estimate their thermal tolerance and their acclimation capability by laboratory experiments; (3) estimate projected losses in climatically suitable habitat; and (4) assess their vulnerability to climate change and provide management strategies. Overall, we expect to make a substantial advance in the knowledge of the drivers of vulnerability to projected climate change in high-mountain freshwater taxa, including the design of specific conservation strategies. https://mountainbeetles.wixsite.com/main/alpinediving

Metacommunity ecology is a recently emerged subdiscipline of ecology, where dispersal among sites is considered a key to understand local biological communities, besides of biological interactions and environmental conditions. Metacommunity, a set of local communities that are linked by dispersal of multiple potentially interacting species, has been studied intensively in temporary freshwater rockpools systems by its special characteristics: patchy distribution, small size and simple structure and communities. In these ecological systems species-sorting and dispersal processes are the principal mechanisms structuring metacommunities of organisms with passive dispersal. However, little is kwon about the spatial patterns of distribution, abundance and interaction of organisms at local, as well as, regional scales of macroinvertebrate communities, especially insects, in the highly dynamic and multistressing marine supralittoral rockpools, and the relative importance of underlying processes. In these habitats, local abiotic conditions (salinity, temperature, desiccation, wind and wave disturbance) can impose important filters affecting the community (species sorting process), although other processes as niche differentiation or priority effects (i.e., competitive dominance given by early colonization) can also be relevant in the on species cooccurrence. In this project, we will especially focus on Ochthebius quadricollis and O. subinteger (F. Hydraenidae) two coexisting water beetles living in Mediterranean coastal rockpools. Both species have flight dispersal ability, but presumably low dispersal ability to large distances and, consequently, a high genetic variability among populations. Thus, this case study offers an ideal framework for integrating population genetic, ecophysiology and metacommunity ecology to explore spatial structure of beetle populations and understanding how local and regional factors interact to drive patterns of species coexistence and macroinvertebrate diversity. We will address four specific aims: O1. To determine geographical range and spatial patterns in the genetic diversity of populations of the two focal species of Ochthebius and the importance of spatial and environmental variables explaining these patterns. O2. To compare multi-stress tolerance of focal species. O3. To identify mechanisms of coexistence of both Ochthebius species (habitat filtering, niche differentiation, founder effects) through field co-ocurrence patterns, competition experiments and the characterization of their ecological niche. O4. To study spatial patterns and processes driving metacommunity structure of macroinvertebrates at local and regional scales (alpha, beta and gamma diversity).

One of the main challenges in disciplines such as ecology, biogeography, conservation and evolutionary biology is to understand and predict how species will respond to environmental changes, specially within a climate change context. Thus, in order to make informed decisions, policymakers need accurate predictions of species responses. To minimize uncertainties in predictions, we focus on deep subterranean environment because i) it is one of the few ecosystems in nature whose environmental conditions are as homogeneous as could be obtained in a laboratory, ii) their species cannot accommodate to changing conditions by behavioural plasticity, dispersal or microhabitat use, and the only possibility to cope with climate change for these species is to persist in situ. Other than to exemplify general principles, subterranean fauna is certainly of interest and value on its own, as they represent an often neglected but substantial portion of Iberian biodiversity. On the other hand, physiological approaches are being increasingly recognized as essential tools to predict vulnerability to climate change, being specially relevant for poor dispersal species. The hypotheses established for this proposal are based on the exciting results obtained in some of our previous studies. In these studies, we did not find differences between thermal tolerances of different subterranean beetles living under different environmental conditions, suggesting a lack of evolutionary adjustment to ambient temperature for these species. This could be due to these species have lost some of the physiological mechanisms related to thermal tolerance due to their likely metabolic cost in a stable environment but with severe resource restrictions. However, the question remains is to what extent this surprising narrow and homogeneous thermal niche is common for the whole subterranean biodiversity, and how this issue could determine the fate of subterranean biodiversity to climate change. Besides, other exciting evolutionary and ecological related questions could be also resolved once physiological data for a greater number of subterranean species becomes available. In this proposal, we aim to test for the generality of these exciting previous findings by studying the thermal niche (species acclimation abilities and thermal tolerances) of different lineages of cave beetles with different degrees of specialization to subterranean environments and from different geographical areas (Pyrenees and Cantabrian Mountains). For this, we will use both long and short term physiological experiments. Finally, we aim to assess the capability to face climate change of different species and populations using the physiological information gathered for the previous objectives. The results of this project could provide important insights to improve our ability i) to understand changes in thermal niche during the process of colonization of deep subterranean environments and ii) to predict changes in biological communities that are exposed to global warming effects. Thus, contrary to the general theory that high altitude species will be at high extinction risk under future climatic conditions, we could demonstrate that subterranean species living in warmer areas will be the most vulnerable to an increase of temperature. The lack of adjustment also could mean that for those species already close to the upper limit of their fundamental niches, the possibilities of survival are severely limited.