Thermal Tolerance and Preferred Temperature in the Critical Endangered Montseny Brook Newt (Calotriton arnoldi).

Climate change, driven by increased human greenhouse gas emissions since the beginning of the industrial revolution up to the present day, is considered one of the major threats to biodiversity in the twenty-first century. One of the most affected groups is the ectotherms due to their direct dependence on environmental temperatures. In recent years, several studies have analysed the effects of temperature and thermal tolerance on several species of ectotherms. However, there are species whose thermal tolerances are still unknown. Such is the case of the critically endangered species, the Montseny Brook Newt (Calotriton arnoldi), endemic to the Montseny massif in Spain and whose thermal biology is unknown. Its critical situation makes it essential to know its tolerance to cooling, warming and thermopreferendum in water environments where the newt lives. Three experimental procedures were conducted from the western and eastern subspecies of C. arnoldi, considering four classes separately (males, females, juveniles and larvae). The results obtained showed that the CTmax of the species exceeded 31 °C, with a significant difference between the two subspecies. We found that the species tolerates low temperatures (<1 °C) well because the genera Calotriton is adapted to live in cold waters with temperatures below 15 °C. Although the thermopreference of the species was expected to trend to cold temperatures, some individuals chose relatively high temperatures, obtaining a range of 11.7 °C to 21.6 °C. The results presented in this study are an advance in the knowledge of the thermal physiology of this species and support the importance of the temperature of the torrent on its survival. Knowing their thermal limits and their preferred temperature range will help to propose management measures that promote the conservation of streams and riparian forest cover to mitigate temperature increases due to climate change.

Surviving on the edge: present and future effects of climate warming on the common frog (Rana temporaria) population in the Montseny massif (NE Iberia).

The Montseny massif shelters the southernmost western populations of common frogs (Rana temporaria) that live in a Mediterranean climate, one which poses a challenge for the species' persistence in a scenario of rising temperatures. We evaluated the effect of climate change at three levels. First, we analysed if there has been an advancement in the onset of spawning period due to the increase in temperatures. Second, we analysed the impact of climatic variables on the onset of the spawning period and, third, how the distribution of this species could vary according to the predictions with regard to rising temperatures for the end of this century. From 2009 to 2021, we found there had been an increase in temperatures of 0.439 °C/decade, more than the 0.1 °C indicated by estimates for the second half of the previous century. We found an advancement in the onset of the reproduction process of 26 days/decade for the period 2009-2022, a change that has been even more marked during the last eight years, when data were annually recorded. Minimum temperatures and the absence of frost days in the week prior to the onset of the spawning period determine the start of reproduction. Predictions on habitat availability for spawning provided by climatic niche analysis for the period 2021-2100 show a potential contraction of the species range in the Montseny and, remarkably, much isolation from the neighbouring populations.

Northward shifts of the distributions of Spanish reptiles in association with climate change.

It is predicted that climate change will drive extinctions of some reptiles and that the number of these extinctions will depend on whether reptiles are able to change their distribution. Whether the latitudinal distribution of reptiles may change in response to increases in temperature is unknown. We used data on reptile distributions collected during the 20th century to analyze whether changes in the distributions of reptiles in Spain are associated with increases in temperature. We controlled for biases in sampling effort and found a mean, statistically significant, northward shift of the northern extent of reptile distributions of about 15.2 km from 1940-1975 to 1991-2005. The southern extent of the distributions did not change significantly. Thus, our results suggest that the latitudinal distributions of reptiles may be changing in response to climate change.

Global Warming and Long-Distance Spread of Invasive Discoglossus pictus (Amphibia, Alytidae): Conservation Implications for Protected Amphibians in the Iberian Peninsula.

Discoglossus pictus is a North African amphibian that was introduced in southern France early the 20th century and has spread south and north along the Mediterranean coastal plains up to 170 km. In order to disentangle the conservation implications of the spread of D. pictus for sensitive native species, we examined the impact of long-term climate warming on the basis of niche overlap analysis, taking into account abiotic factors. The study area covered the distribution ranges of all genus Discoglossus species in northwestern Africa (659,784 km2), Sicily (27,711 km2), the Iberian Peninsula, and southern France (699,546 km2). Niche overlap was measured from species environmental spaces extracted via PCA, including climate and relief environmental variables. Current and future climatic suitability for each species was assessed in an ensemble-forecasting framework of species distribution models, built using contemporary species data and climate predictors and projected to 2070's climatic conditions. Our results show a strong climatic niche overlap between D. pictus and native and endemic species in the Iberian Peninsula. In this context, all species will experience an increase in climatic suitability over the next decades, with the only exception being Pelodytes punctatus, which could be negatively affected by synergies between global warming and cohabitation with D. pictus.

Future hydrological constraints of the Montseny brook newt (Calotriton arnoldi) under changing climate and vegetation cover.

The Montseny brook newt (Calotriton arnoldi) is a critically endangered amphibian species which inhabits a small 20 km2 holm oak and beech forest area in NE Spain. Calotriton arnoldi strictly lives in running waters and might be highly vulnerable to hydrological perturbations expected to occur under climate and vegetation cover changes. Knowledge about the potential response of the species habitat to environmental changes can help assessing the actions needed for its conservation. Based on knowledge of the species and supported by observations, we proposed daily low and high streamflow event thresholds for the viability of C. arnoldi. We used the rainfall-runoff model PERSiST to simulate changes in the frequency and duration of these events, which were predicted under two climate and four vegetation cover scenarios for near-future (2031-2050) and far-future (2081-2100) periods in a reference catchment. All future scenarios projected a significant decrease in annual streamflow (from 21% to as much as 67%) with respect to the reference period. The frequency and length of low streamflow events will dramatically increase. In contrast, the risk of catastrophic drift linked to high streamflow events was predicted to decrease. The potential change in vegetation toward an expansion of holm oak forests will be more important than climate changes in determining threshold low flow conditions. We thus demonstrated that consideration of potential changes in vegetation and not only changes in climate variables is essential in simulating future streamflows. This study shows that future low streamflow conditions will pose a severe threat for the survival of C. arnoldi and may help taking management actions, including limiting the expansion of holm oak forest, for ameliorating the species habitat and help its conservation.

Structure and dynamics of an amphibian metacommunity in two regions.

1. The concept of metacommunity is based on the hypothesis that species occurrence depends on species dynamics and interactions on local and regional scales via the movements of individuals between localities. Metacommunity approaches are currently being applied to pond breeding taxa such as amphibians. 2. Given that animal movement is also influenced by the physical quality of the matrix to be crossed to reach a breeding habitat and by the affinity of the species for specific terrestrial habitats, matrix characteristics may enhance or hinder dispersal success. These characteristics would, in turn, affect the composition of larval assemblages at local level and, consequently, determine metacommunity structure and dynamics. 3. Here we compared the structures and dynamics of two metacommunities with the same pool of anurans along similar freshwater gradients in two regions that are well differentiated in terms of their respective terrestrial matrix. 4. Abundance of tadpole species and species assemblage in the two regions were determined principally by local processes (at pond level); however, the structure and dynamics of the communities differed. In one region species abundance was explained in part by landscape factors and consequently showed lower co-occurrence and lower colonization rates (species sorting models) indicating that terrestrial habitat could restrict animal movements, whereas in the other region higher co-occurrence and higher colonization rates (mass effect models) indicated low dispersal limitations.