Luis Albero

Amphibians are facing large population declines as a result of both natural and anthropogenic threats. Reconstructing and understanding the composition and structure of amphibian communities is essential for developing effective monitoring and conservation strategies. In this study, we compared environmental DNA metabarcoding (eDNA‐MB) data with a comprehensive dataset obtained from acoustic and visual encounter surveys (AVES) in a set of Mediterranean ponds. Additionally, we designed and validated a quantitative PCR (qPCR) assay for the Iberian ribbed newt ( Pleurodeles waltl ) and tested its ability with eDNA‐MB and AVES in assessing the presence and population densities of this species. Our findings provide evidence that eDNA‐MB can be a valuable method for reconstructing the composition and structure of amphibian communities. eDNA‐MB identified all expected amphibian species from the regional species pool, including some that were missed in traditional surveys. Although eDNA‐MB abundance estimations for P. waltl seemed virtually independent of population densities obtained through field surveys, we found a significant association between eDNA concentration (qPCR) and AVES abundance estimates. Our findings suggest that effective strategies for amphibian biomonitoring need the combination of community data obtained from both traditional and eDNA surveys, especially in the Mediterranean region where strong environmental constraints can affect the detection and persistence of eDNA in freshwater ecosystems.

Context: Functional connectivity across fragmented habitat patches is essential for the conservation of animal populations in humanized landscapes. Given their low dispersal capacity, amphibians in the Mediterranean region are threatened by habitat fragmentation and loss due to changes in land use, including agricultural intensification. Objectives: We assessed patterns of functional connectivity of a Near Threatened Mediterranean amphibian, the sharp ribbed newt (Pleurodeles waltl), in an agricultural landscape matrix in NW Spain subject to different intensification regimes. Methods: We sampled newts in 17 ponds embedded in a terrestrial habitat matrix dominated by agricultural land uses. Genome-wide molecular markers (1390 SNPs) were used to assess patterns of genetic diversity and gene flow among ponds. We tested the role of landscape features on functional connectivity using isolation by resistance models incorporating information on Normalized Difference Vegetation Index (NDVI) data. Results: We found low levels of genetic diversity in all sampled populations. Global F_ST estimates and cluster analyses revealed shallow but significant genetic structure in the study area, with NDVI-based resistance models showing that open areas (rainfed crops and grasslands) offer lower resistance to gene flow and thus promote functional connectivity among demes. Conclusions: Our study highlights the important role of landscape features, such as open areas resulting from traditional rainfed agriculture, in promoting functional connectivity between amphibian populations in Mediterranean agrosystems. Conservation policies must adopt a functional network strategy and protect groups of inter-connected temporary ponds across the traditional agricultural matrix to efficiently preserve their associated biotic communities.

Water supplies in arid regions have traditionally been assured by cisterns, channels, wells, among other man-made structures with smooth vertical walls that can be deadly traps for several animals, including amphibians and reptiles. In this study, we investigate the incidence of such “trap structures” on the herpetofauna of the eastern Iberian Peninsula. We explored which features of these structures and which biological traits are associated with higher incidence of falling into these traps. We studied 205 trap structures and found 1224 amphibians or reptiles representing 25 different species, including endangered and protected ones. Broad-scale macroclimate and landscape variables were not associated with the incidence of traps. Instead, trap impact was influenced mainly by trap morphology and season of the year, which suggests that construction design and species phenology are the main factors to affect the incidence of a trap. Biological traits (subterranean or aquatic habits, diet, nocturnal activity or emission of reproductive calls) in some species were related to the probability of falling into these traps. Some species of snakes, lizards, and toads were more prone to fall in trap structures than other species. We conclude that trap structures can strongly impact amphibian and reptile survival, especially in arid or semi-arid regions where wells and water cisterns are widespread.

Agricultural intensification has been associated with biodiversity declines, habitat fragmentation and loss in a number of organisms. Given the prevalence of this process, there is a need for studies clarifying the effects of changes in agricultural practices on local biological communities; for instance, the transformation of traditional rainfed agriculture into intensively irrigated agriculture. We focused on pond-breeding amphibians as model organisms to assess the ecological effects of agricultural intensification because they are sensitive to changes in habitat quality at both local and landscape scales. We applied a metacommunity approach to characterize amphibian communities breeding in a network of ponds embedded in a terrestrial habitat matrix that was partly converted from rainfed crops to intensive irrigated agriculture in the 1990s. Specifically, we compared alpha and beta diversity, species occupancy and abundance, and metacommunity structure between irrigated and rainfed areas. We found strong differences in patterns of species occurrence, community structure and pairwise beta diversity between agricultural management groups, with a marked community structure in rainfed ponds associated with local features and the presence of some rare species that were nearly absent in the irrigated area, which was characterized by a random community structure. Natural vegetation cover at the landscape scale, significantly lower on the irrigated area, was an important predictor of species occurrences. Our results suggest that maintaining both local and landscape heterogeneity is key to preserving diverse amphibian communities in Mediterranean agricultural landscapes.