Juan Francisco Beltrán

Acknowledging biodiversity within the Linnaean classification system is essential to ensure its consideration in natural history research and conservation, especially as unnamed entities are often ...

Speciation, i.e., the formation of new species, implies that diverging populations evolve genetic, phenotypic or ecological factors that promote reproductive isolation (RI), but the relative contributions of these factors remain elusive. Here we test which of genomic, bioacoustic, morphological, and environmental differences best predicts RI across a continuum of divergence in the midwife toads (genus Alytes), a group of Western Mediterranean amphibians, using a total evidence approach. We found that, without strong geographic barriers to dispersal, the extent of introgression across hybrid zones between phylogeographic lineages, which should reflect the strength of RI, predominantly covaries with genomic divergence. Overall phenotypic differentiation becomes substantial only between well established, fully isolated species. These results suggest that speciation in midwife toads initially involve cryptic lineages, which probably evolve RI through intrinsic (genetic) hybrid incompatibilities. As they continue to diverge, these nascent species eventually differentiate externally, which potentially enforces pre‐mating barriers and facilitates sympatry. This speciation scenario has practical implications for species delimitation, notably when using hybrid zones and divergence thresholds as proxies for reproductive isolation.

In their recent paper, Van Hassel and Bovenkerk

Species distribution models (SDMs) are a key tool for biogeography and climate change research, although current approaches have some significant drawbacks. The use of species occurrence constrains predictions of correlative models, while there is a general lack of eco‐physiological data to develop mechanistic models. Passive acoustic monitoring is an emerging technique in ecology that may help to overcome these limitations. By remotely tracking animal behaviour across species geographical ranges, researchers can estimate the climatic breadth of species activity and provide a baseline for refined predictive models. However, such integrative approach still remains to be developed. Here, we propose the following: (a) a general and transferable method to build acoustic SDMs, a novel tool combining acoustic and biogeographical information, (b) a detailed comparison with standard correlative and mechanistic models, (c) a step‐by‐step guide to develop aSDMs and (d) a study case to assess their effectiveness and illustrate model outputs, using a year‐round monitoring of calling behaviour of the Iberian tree frog at the thermal extremes of its distribution range. This method aims at forecasting changes in environmental suitability for acoustic communication, a key and climate‐dependent behaviour for a wide variety of animal taxa. aSDMs identified strong associations between calling behaviour and local environmental conditions and showed robust and consistent predictive performance using two alternative models (regression and boundary). Furthermore, these models better captured climatic variation than correlative models as they use observations at higher temporal resolution. These results support aSDMs as efficient tools to model calling behaviour under future climate scenarios. The proposed approach offers a promising basis to explore the capacity of vocal species to deal with climate change, supported by an innovative integration of two disciplines: bioacoustics and biogeography. aSMDs are grounded on ecologically realistic conditions and provide spatially and temporally explicit predictions on calling behaviour, with direct implications in reproduction and survival. This enables to precisely forecast shifts in breeding phenology, geographic distribution or species persistence. Our study demonstrates how acoustic monitoring may represent an increasingly valuable tool for climate change research.

Global change is impacting our lives in many ways

Competition, predation, and diseases are key factors shaping animal communities. In recent decades, lagomorphs in Europe have been impacted by virus-borne diseases that have caused substantial declines in their populations and, subsequently, in many of their predators. We examined activity and habitat-use patterns of sympatric European rabbits (Oryctolagus cuniculus L.) and Iberian hares (Lepus granatensis R.) in Doñana National Park, Spain, (DNP) during two periods of disease outbreak. In the first period (1984–1985), fecal pellet counts and roadside counts indicated that lagomorph species were segregated, with rabbits occurring in scrublands and hares in marshlands. Both species also occupied rush and fern belt ecotones. Roadside counts at sunrise, midday, sunset, and midnight revealed that rabbits and hares had the same activity patterns (crepuscular and nocturnal) in the zone of sympatry. During the second period (2005–2016), roadside counts showed that rabbits and hares were mainly nocturnal in scrublands and border marshlands. Hares occupied scrublands; a habitat previously occupied only by rabbits. These results are interpreted in light of the competition theory and predation pressure. The disease-caused decline of rabbits has likely favored hares that moved into scrublands, a vegetation type previously occupied exclusively by rabbits. The decline of rabbits in DNP has also caused the almost disappearance of this area of the Iberian lynx (Lynx pardinus), a rabbit specialist, thus enabling generalist predators to increase. Generalist predators have subsequently increased predation pressure on both rabbits and hares, causing them to switch to nocturnal activity.

Cyber-physical systems (CPS) constitute a promising paradigm that could fit various applications. Monitoring based on the Internet of Things (IoT) has become a research area with new challenges in which to extract valuable information. This paper proposes a deep learning classification sound system for execution over CPS. This system is based on convolutional neural networks (CNNs) and is focused on the different types of vocalization of two species of anurans. CNNs, in conjunction with the use of mel-spectrograms for sounds, are shown to be an adequate tool for the classification of environmental sounds. The classification results obtained are excellent (97.53% overall accuracy) and can be considered a very promising use of the system for classifying other biological acoustic targets as well as analyzing biodiversity indices in the natural environment. The paper concludes by observing that the execution of this type of CNN, involving low-cost and reduced computing resources, are feasible for monitoring extensive natural areas. The use of CPS enables flexible and dynamic configuration and deployment of new CNN updates over remote IoT nodes.

The developmental and biochemical mechanisms of colour change through chromatophore metachrosis in amphibian tadpoles are relatively well studied, but the environmental factors driving colour change remain unclear. A cryptic response to background colour in order to reduce predation is an intuitively valid explanation, however, other hypotheses need to be explored. In this study, we aimed to investigate the environmental factors driving the melanophore metachrosis process in Alytes dickhilleni tadpoles. First, we tested the response to two backgrounds with clearly distinct reflectance: black and white. The proportion of dark tadpoles became significantly higher when they were located on the black background, and pale tadpole proportion was dominant on the white background, as expected from the crypsis hypothesis. Secondly, we added two new factors, temperature and photoperiod, maintaining the background variation. Our results suggest that lower temperatures, and short photoperiods were significantly driving a change to dark colouration in tadpoles, possibly allowing a more efficient thermoregulation, and in consequence, development and growth. Next we tested whether dark and pale tadpoles selected backgrounds that matched their colouration (black and white background), and found no evidence for behavioral selection. The apparent response in colour change to background appears to be mediated by the background reflectance of light, that there does not seem to be behavioral selection of matching background by the tadpoles, and therefore it suggests that color change is more likely to be a physiological response with thermoregulatory implications.

Variation and population structure play key roles in the speciation process, but adaptive intraspecific genetic variation is commonly ignored when forecasting species niches. Amphibians serve as excellent models for testing how climate and local adaptations shape species distributions due to physiological and dispersal constraints and long generational times. In this study, we analysed the climatic factors driving the evolution of the genus Alytes at inter- and intraspecific levels that may limit realized niches. We tested for both differences among the five recognized species and among intraspecific clades for three of the species (Alytes obstetricans, A. cisternasii, and A. dickhilleni). We employed ecological niche models with an ordination approach to perform niche overlap analyses and test hypotheses of niche conservatism or divergence. Our results showed strong differences in the environmental variables affecting species climatic requirements. At the interspecific level, tests of equivalence and similarity revealed that sister species were non-identical in their environmental niches, although they neither were entirely dissimilar. This pattern was also consistent at the intraspecific level, with the exception of A. cisternasii, whose clades appeared to have experienced a lower degree of niche divergence than clades of the other species. In conclusion, our results support that Alytes toads, examined at both the intra- and interspecific levels, tend to occupy similar, if not identical, climatic environments.