BUSCADOR RECOLECTA

Ample variation in body size is common in vertebrates over extensive geographical distances, or in isolated populations, where effective geographical barriers may cause dwarfism or gigantism. Here we study potential causes of extreme size reduction in continental populations of amphibians within a short geographical distance and in the absence of geographical barriers. Natterjack toads Epidalea calamita in Doñana National Park (Spain) experience up to 2.1-fold difference in body mass in as little as 37 km. Studying six populations divergent in body size, we tested for genetic isolation of the dwarf populations using multilocus genotypes (16 microsatellites), and explored whether populations differ in trophic status (through stable isotope analysis), standard metabolic rate and growth pattern, senescence and age structure (conducting telomere length assays and skeletochronology). We also recorded advertisement calls across populations and experimentally tested for behavioural reinforcement of the body size variation through female preferences. Local dwarfism in these populations occurs in the absence of genetic isolation while maintaining relatively high effective population sizes. Dwarf populations, however, are exposed to drier and warmer climatic conditions, have different trophic status, show lower mass-specific metabolic rate, and male advertisement calls with a higher dominant frequency. Juvenile growth differed among populations, reaching the adult stage at different body sizes. Altogether, our results suggest a significant influence of environmental conditions on the physiology and ecology of the Doñana E. calamita populations, mainly affecting toads between metamorphosis and sexual maturity. Further experimental and genomic studies focusing on these early life stages are necessary to dissect the relative roles of the environment and adaptive genetic differentiation on this phenomenon., This project was funded by Plan Nacional (grant CGL2014-59206-P). LHJ was supported by a predoctoral fellowship (BES-2015-074463) provided by the Spanish Ministry of Economy and Competitiveness.

In temporary ponds, submerged plants have adapted to recurrent periods of drought. These ponds often lack the impact of large herbivores but can harbor large numbers of herbivorous tadpoles. Tadpoles of the Iberian spadefoot toad (Pelobates cultripes) may reach large body size and consume large quantities of macrophytes during their long larval period, which is shortened with risk of pond drying. We conducted a mesocosm experiment to analyze the interplay between hydroperiod and impact of herbivorous tadpoles on the abundance and life history of 3 species of submerged plants common to temporary ponds. We observed differences in growth among plant species resulting in lags in timing of maximum cover, probably related to interspecific competitive interactions. Some plants responded to pond drying with a remarkable increase in the production of flowers. Tadpoles greatly reduced the plant cover, although their impact varied across plant species. Differential plant consumption by these large tadpoles can substantially modify the internal structure and complexity of temporary ponds, and tadpoles can also interfere with plant responses to shortened hydroperiod., Peer reviewed

Phenotypic plasticity allows organisms to improve the match between their phenotype and heterogeneous environments. Theoretical models have argued that costs of maintaining the sensory and response machinery necessary for adaptive phenotypic plasticity are important determinants to the evolution of plasticity. Despite recurrent arguments invoking putative metabolic costs associated with maintenance of cellular machinery, no studies have yet attempted to quantify it from a molecular standpoint. Here we experimentally examine physiological differences across genotypes (sibships) of spadefoot toad larvae with different degrees of plasticity in response to predator cues. We observed marked differences across sibships in developmental, growth and morphological responses to predators, and tested whether increased plasticity was associated with oxidative stress or immune suppression. We observed that more plastic sibships experienced higher antioxidant enzymatic activity when reared in the absence of predator cues, i.e. not expressing their plastic responses. The degree of plasticity was also associated with higher lipid peroxidation and slightly greater granulocyte-to-lymphocyte ratio. Higher antioxidant activity in highly plastic sibships suggests that maintenance of phenotypic plasticity may be linked to energy demanding metabolic processes. Our findings suggest that having the potential to produce plastic responses may incur oxidative and immunological costs. In the long term, such maintenance costs may erode individual fitness and even constrain the evolution of plasticity. To our knowledge, this is the first empirical evidence indicating the existence of a physiological cost to the maintenance of phenotypic plasticity., This study was funded by Ministerio de Economía y Competitividad (grants CGL2012-40044 and CGL2014-59206-P). PB was supported by fellowship F.P.U.-AP2010-5373 from the Ministerio de Educación and by a Marie Curie Fellowship METAGE-797879. Laboratory facilities were provided by ICTS-RBD., Peer reviewed

Among invasive species, floating plants have a great impact on aquatic ecosystems, forming dense mats that cause a great alteration of the physical and chemical water features. We experimentally assessed the effect of Azolla filiculoides mats on Mediterranean temporary waters using mesocosms with sediments from an invaded marsh and amphibian larvae from surrounding wetlands. Azolla filiculoides formed a dense mat over the water surface in the experimental tanks, which decreased pH and oxygen concentration, and increased nutrients, nitrogen and phosphorus compounds in the water compared to mesocosms lacking the exotic fern. Macrophyte abundance and richness were reduced under the Azolla mat. Invaded mesocosms also had higher phytoplankton abundance and different zooplankton composition, which was mainly characterized by higher abundance of juvenile copepods. Regarding amphibian development, tadpoles requiring a long developmental period, the western spadefoot toad, Pelobates cultripes, had significantly lower survival in the presence of A. filiculoides (4.8% compared to 60% survival in fern-free mesocosms). For tadpoles of the Mediterranean tree frog, Hyla meridionalis, which develop faster, we did not detect effects on survival, but on body size and physical condition of metamorphs. The formation of A. filiculoides mats produced a deterioration of the trophic web, as it caused most sources to be depleted in 13C and 15N. Primary consumers, tadpoles and zooplankton, were also 13C depleted, although the diet of tadpoles from Azolla mesocosms was mainly composed of the invasive fern. We therefore conclude that A. filiculoides has a negative impact on physical and chemical water features, reduces the richness and biomass of the submerged macrophyte guild and reduces survival and body condition of tadpoles. Overall, A. filiculoides causes substantial deterioration of the food web of the aquatic ecosystem., The study was funded by the Spanish Ministry of Economy and Competitiveness (Project CGL2014-59206-P), and fellowship to MJP-R (BES-2013-213 064954). The staff of the Doñana Biological Reserve (ICTS-RBD) provided logistical support. The study was approved by the Ethics Committee for Animal Care at the Estación Biológica de Doñana (CEBA-EBD 12-53) and the regional government of Andalucía (SGYB/FOA/AFR/CFS)., Peer reviewed

Climatic data was obtained from Worldclim Version 1&2, soil data from the European Soil Database, and Normalized Difference Vegetation Indices (NDVI) from satellite images through the Modis Vegetation index MOD13Q1.
For skeletochronology, telomere, and microsatellite analyses we collected a total of 180 Epidalea calamita adult males across all populations. We then clipped the fourth toe of the right hindlimb that we then used for cross sectioning and DNA extractions.
Stable isotope data were obtained from E. calamita egg clutches, which allows direct assessment of the diet of the female without harming any adults. We collected small sections of egg clutches that were kept under identical conditions in the lab until hatching and then determined the carbon and nitrogen levels of these samples.
Standard metabolic rate was assessed in a terrestrial respirometer overnight, for which we brought in mature males from the field at night. Advertisement calls were recorded using a shotgun microphone and subsequently analysed using the software Raven Pro v.1.4. For female behavioural assays we brought in receptive females at night to the lab and played back recorded calls. All individuals were released at dawn and no individual was harmed., This dataset consists of a single excel file split into distinct sheets for different types of data: climate, population genetics, stable isotopes, standard metabolic rate, skeletochronology, telomere length, male advertisement calls, and female preference tests. The climatic data is split into sheets for NDVI, Worldclim Bio19, and edaphology. The population genetics data is split into sheets for basic statistics, genetic differentiation indicators, isolation by distance, and effective population size., Plan Nacional (grant CGL2014-59206-P), No