Europe’s obligate cave-dwelling amphibian Proteus anguinus inhabits subterranean waters of the north-western Balkan Peninsula. Because only fragments of its habitat are accessible to humans, this endangered salamander’s exact distribution has been difficult to establish. Here we introduce a quantitative real time polymerase chain reaction-based environmental DNA (eDNA) approach to detect the presence of Proteus using water samples collected from karst springs, wells or caves. In a survey conducted along the southern limit of its known range, we established a likely presence of Proteus at seven new sites, extending its range to Montenegro. Next, using specific molecular probes to discriminate the rare black morph of Proteus from the closely related white morph, we detected its eDNA at five new sites, thus more than doubling the known number of sites. In one of these we found both black and white Proteus eDNA together. This finding suggests that the two morphs may live in contact with each other in the same body of groundwater and that they may be reproductively isolated species. Our results show that the eDNA approach is suitable and efficient in addressing questions in biogeography, evolution, taxonomy and conservation of the cryptic subterranean fauna.

Although poleward range expansions are commonly attributed to global change, a complex interaction of ecological and evolutionary factors might contribute to expansion success. Here, we study the expansion of the yellow sac spider Cheiracanthium punctorium, a medically important species in Central Europe. Using microsatellite markers and DNA sequences, morphological and climate niche analyses, we identify factors associated with the spider's expansion success. Our results indicate that the species' initial expansion has been triggered by environmental change and preadaptation in the source populations. However, despite extensive gene flow, expanding populations maintain genetic and morphological differentiation from native ones, which is correlated with climatic niche differences. Moreover, expanding spiders might have temporarily escaped an eggsac parasite that causes high mortality in the native range. Hence, our results paint a complex picture of diverse factors associated with expansion success. We speculate that expanding populations might be capable of adapting to novel ecological conditions in northern Europe. This could allow a substantial range expansion, much farther than by environmental change alone. Our distribution model predicts that the spider will soon massively spread over most of northern Europe, bringing along considerable health concerns.

Geodiversity, a relatively new concept in earth sciences, synthesizes information related to abiotic layers and indicates their spatial interactions and interrelations. Geodiversity has been used in mountainous areas to assess both their ecological and economic potential. In this paper, we link geodiversity analysis with a multi-resolution wavelet transform to parse the hidden patterns of geodiversity of a plateau area from the Swiss Jura Mountains. We decomposed a high-resolution digital terrain model using a fractional spline wavelet transform method into four coarser resolution images, ranging from 4 to 32 m, to detect image discontinuities. This generated directional high-pass coefficients, which accumulated in a bottom-up approach to determine the terrain roughness and extract obvious topographical features. In addition, we mapped and quantified total geodiversity using available geological, tectonical and topographical elements on a 32-m square grid. The geodiversity index of the area was computed by adding the terrain roughness derived from a wavelet transform to the traditional formula. The correlation among the geodiversity index, terrain roughness, elevation and slope data was tested with exploratory regression and Spatial Lag regression models. We obtained four images that represent the wavelet-detected terrain roughness at four levels of decomposition, ranging from 4 to 32 m. The geodiversity index, computed based on the wavelet-detected roughness, accurately refined the results obtained with the total geodiversity traditional formula. The distribution of the wavelet-detected topographical features was more heterogenic, with a coarser map resolution and forming areas that correspond to the mapped areas with the most obvious geodiversity patterns. Our findings provide a tool for detecting hidden geodiversity patterns within areas that lack apparent landscape variability, as well as for overcoming traditional methods for assessing geodiversity by introducing the multiscale fractional spline wavelet transform with accurate mapping of the terrain roughness.

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Background Lightless caves can harbour a wide range of living organisms. Cave animals have evolved a set of morphological, physiological, and behavioural adaptations known as troglomorphisms, enabling their survival in the perpetual darkness, narrow temperature and humidity ranges, and nutrient scarcity of the subterranean environment. In this study, we focused on adaptations of skull shape and sensory systems in the blind cave salamander, Proteus anguinus, also known as olm or simply proteus—the largest cave tetrapod and the only European amphibian living exclusively in subterranean environments. This extraordinary amphibian compensates for the loss of sight by enhanced non-visual sensory systems including mechanoreceptors, electroreceptors, and chemoreceptors. We compared developmental stages of P. anguinus with Ambystoma mexicanum, also known as axolotl, to make an exemplary comparison between cave- and surface-dwelling paedomorphic salamanders. Findings We used contrast-enhanced X-ray computed microtomography for the 3D segmentation of the soft tissues in the head of P. anguinus and A. mexicanum. Sensory organs were visualized to elucidate how the animal is adapted to living in complete darkness. X-ray microCT datasets were provided along with 3D models for larval, juvenile, and adult specimens, showing the cartilage of the chondrocranium and the position, shape, and size of the brain, eyes, and olfactory epithelium. Conclusions P. anguinus still keeps some of its secrets. Our high-resolution X-ray microCT scans together with 3D models of the anatomical structures in the head may help to elucidate the nature and origin of the mechanisms behind its adaptations to the subterranean environment, which led to a series of troglomorphisms.