It is difficult to obtain evidence of population trends for some animals due to their elusive behaviour and/or low density, hindering the acquisition of quantitative data to measure population size ...that would allow an evaluation of their vulnerability. This is the case for top predators such as snakes. This study explores the usefulness of citizen-science datasets, gathered between 1980 and 2018, in two large regions of southwestern Europe (Spain and the area of Languedoc-Roussillon in southern France) to estimate long-term snake population trends. We used the TRIM (Trends and Indices for Monitoring data) program to analyse trends in 14 snake species during the chronosequence, and modelled the response of each species (the slope of the trend) with a generalized linear mixed model (GLMM) in order to identify the functional traits that explain population trends. Overall, the results showed a general decline of snake fauna in both regions. The GLMM detected that this decline is attenuated in Eurosiberian species compared to Mediterranean species, as well as in species that dwell in forested habitats. The open Mediterranean landscapes in both study regions have been anthropically transformed, and the pressure on their biota has accelerated over recent decades due to habitat loss and degradation. This degradation is affecting Mediterranean organisms such as snakes. The framework we developed allows citizen-science data to be used as a tool to detect population trends and to apply IUCN criterion A (Population size reduction) to species with a high level of imperfect detection or that are suspected to be inaccurately ranked in the assessment of their vulnerability.
Trace elements can be toxic when they cannot be easily removed after entering an ecosystem, so a long-term assessment is fundamental to guide ecosystem restoration after catastrophic pollution. In ...1998, a pyrite mining accident in Aznalcóllar (south-western Spain) spilled toxic waste over a large area of the Guadiamar river basin, where, after restoration tasks, the Guadiamar Green Corridor was established. Eight years after the mine accident (2005–2006), the ground-dwelling insectivorous lizard Psammodromus algirus registered high trace-element levels within the study area compared to specimens from a nearby unpolluted control site. In 2017, 20 years after the accident, we repeated the sampling for this lizard species and also quantified trace elements in vegetation as well as in arthropod samples in order to identify remnant trace-element accumulation with the aim of assessing the transfer of these elements through the trophic web. We found remnant trace-element contamination in organisms of the polluted site compared to those from the unpolluted site. All trace-element concentrations were higher in arthropods than in plants, suggesting these compounds bioaccumulate through the trophic web. Lizards from the polluted areas had higher As, Cd, and Hg concentrations than did individuals from the unpolluted area. Lizard abundance between sampling periods (2005–06 and 2017) did not vary in unpolluted transects but strongly declined at polluted ones. By contrast, the Normalized Difference Vegetation Index indicated that in the study period, the vegetation was similar at the two sampling sites. These results suggest that, 20 years after the accident, the trace-element pollution could be the cause of a severe demographic decline of the lizard in the polluted area.
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•Trace elements in three trophic levels were assessed 20 years after a mine spill.•There was an apparent transfer of trace elements from plants to arthropods.•Lizards registered high trace element accumulation for As, Hg, and Cd.•Lizard density strongly declined at the polluted site with respect to the control one.•20 years after the spill, the trace element pollution persists in the Guadiamar basin.
20 years after the mine spill at the Guadiamar basin (southern Spain), plant, arthropod and lizard samples showed high concentration of trace elements, suggesting that the pollution persists.
Fire is one of the main disturbances to terrestrial environments, transforming habitat structure and affecting community composition. Coupled with fire, forest type and vegetation structure modulate ...the taxonomic response to fire by ectotherm organisms such as reptiles. The response of each reptile species to fire is based on their functional attributes, which make some species resilient to fire and others vulnerable to that disturbance and only adapted to long-unburnt landscapes. We studied the functional response of a reptile community at 13 burnt sites within the African rim of the Western Mediterranean, and in two contrasting forest types, i.e. native cork oak forests (five sites) and pine plantations (eight sites). We compiled seven functional traits for the reptile species in the study areas, and quantified reptile functional diversity at each sampled plot. Variation in this index was examined from burnt to nearby unburnt plots, both in cork oak and pine forests, with generalized linear mixed models. Redundancy analysis was used to identify which functional traits were associated with particular plot types. We found 2149 individual reptiles from 15 species. The functional response of reptiles to fire was forest-type dependent: functional richness did not change with fire in cork oak forest plots, but increased with fire in the pine plantation ones. High reptile functional richness in cork oak plots was due to high species richness in this forest type. The functional-redundancy analysis showed that cork oak forest hosts a reptile community functionally composed of small Mediterranean ground- and rock-dwelling lizards. In pine plantation plots, however, saxicolous geckos and phytophagous tortoises indicate the availability of other microhabitat and food resources to be exploited by reptile species with different functional traits.
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•Reptile functional responses to fire have been examined in north-western Africa.•Functional richness was higher in native cork oak forests than in pine plantations.•Functional resilience of reptiles to fire was also higher in cork oak forest.•Pine plantations give few functional opportunities to reptiles.•Burning improves the functional richness of the reptile community in pine plantations
Abstract
The designation of taxonomic units has important implications for the understanding and conservation of biodiversity. Eurasian vipers are a monophyletic group of viperid snakes (Serpentes, ...Viperinae), currently comprising four genera (Daboia, Macrovipera, Montivipera and Vipera) and up to 40 species. Taxonomic units have been described using a wide variety of methods and criteria, and consequently, considerable controversy still surrounds the validity of some currently listed species. In order to promote a consensus- and evidence-based taxonomy of Eurasian vipers, we analysed published mitochondrial and nuclear DNA sequences for this group to reconstruct phylogenetic relationships among currently recognized viper species. We also compiled information on external morphology to assess their morphological distinctiveness. Phylogenetic inference based on mtDNA sequences shows contrasting levels of divergence across genera and species and identifies several instances of non-monophyly in described species. Nuclear DNA sequences show extremely low levels of genetic variation, with a widespread pattern of allele sharing among distant species, and even among genera. Revision of morphological data shows that most species designations rely on scalation traits that overlap extensively among species of the same genus. Based on our combined assessment, we recognize 15 taxa as valid species, three taxa which likely represent species complexes, 17 taxa of doubtful validity as species, and five taxa for which species status is maintained but further research is highly recommended to assess taxonomic arrangements. We stress the need to implement integrative taxonomic approaches for the recognition of evidence-based taxonomic units in Eurasian vipers.
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. Se ha pronosticado que el cambio climático influirá en la extinción de algunos reptiles y que el número de esas extinciones dependerá de la capacidad de los reptiles para cambiar su distribución. Se desconoce si cambiará la distribución latitudinal de reptiles como respuesta a los incrementos de temperatura. Utilizamos datos de distribución de reptiles recolectados durante el siglo 20 para analizar si los cambios en la distribución de reptiles en España están asociados con incrementos de la temperatura. Controlamos los sesgos en el esfuerzo de muestreo y encontramos un cambio significativo, de 15.2 km, hacia el norte de la extensión norteña de las distribuciones de reptiles de 1940-1975 a 1991-2005. La extensión sureña de las distribuciones no cambió significativamente. Por lo tanto, nuestros resultados sugieren que las distribuciones latitudinales de reptiles pueden estar cambiando en respuesta al cambio climático.
The invasive snake
colonized the island of Ibiza (Balearic Islands) in 2003 as stowaways inside trunks of olive trees imported for gardening. It has quickly spread since 2010, posing a threat to the ...island's only remaining endemic vertebrate, the Ibiza wall lizard
. We map the yearly expansion rate of the snake and estimate via transect surveys how severely it affects the distribution and abundance of the endemic lizard. As well, we surveyed 9 of 30 small lizard populations on islets surrounding Ibiza that have been isolated since the Last Glacial Maximum. Snakes had invaded 49% of Ibiza's land area by 2018, and censuses show a critical contrast in lizard abundance between areas with and without snakes; almost all censuses in areas without snakes show lizard presence whereas nearly all censuses in areas with
lack lizard sightings. Moreover, at least one subspecies previously thriving on one of the offshore islets has become extinct, and there have been several snakes recorded swimming between Ibiza and the surrounding islets. Therefore, lizard populations have been dramatically reduced or have vanished within the range of the snake, and our results quantitatively support upgrading this species' threat level for extinction. This study can inform to programs to manage invasive snake populations and to conservation actions to recover the endemic lizard.
ABSTRACT
Deserts and arid regions are generally perceived as bare and rather homogeneous areas of low diversity. The Sahara is the largest warm desert in the world and together with the arid Sahel ...displays high topographical and climatic heterogeneity, and has experienced recent and strong climatic oscillations that have greatly shifted biodiversity distribution and community composition. The large size, remoteness and long‐term political instability of the Sahara‐Sahel, have limited knowledge on its biodiversity. However, over the last decade, there have been an increasing number of published scientific studies based on modern geomatic and molecular tools, and broad sampling of taxa of these regions. This review tracks trends in knowledge about biodiversity patterns, processes and threats across the Sahara‐Sahel, and anticipates needs for biodiversity research and conservation. Recent studies are changing completely the perception of regional biodiversity patterns. Instead of relatively low species diversity with distribution covering most of the region, studies now suggest a high rate of endemism and larger number of species, with much narrower and fragmented ranges, frequently limited to micro‐hotspots of biodiversity. Molecular‐based studies are also unravelling cryptic diversity associated with mountains, which together with recent distribution atlases, allows identifying integrative biogeographic patterns in biodiversity distribution. Mapping of multivariate environmental variation (at 1 km × 1 km resolution) of the region illustrates main biogeographical features of the Sahara‐Sahel and supports recently hypothesised dispersal corridors and refugia. Micro‐scale water‐features present mostly in mountains have been associated with local biodiversity hotspots. However, the distribution of available data on vertebrates highlights current knowledge gaps that still apply to a large proportion of the Sahara‐Sahel. Current research is providing insights into key evolutionary and ecological processes, including causes and timing of radiation and divergence for multiple taxa, and associating the onset of the Sahara with diversification processes for low‐mobility vertebrates. Examples of phylogeographic patterns are showing the importance of allopatric speciation in the Sahara‐Sahel, and this review presents a synthetic overview of the most commonly hypothesised diversification mechanisms. Studies are also stressing that biodiversity is threatened by increasing human activities in the region, including overhunting and natural resources prospection, and in the future by predicted global warming. A representation of areas of conflict, landmines, and natural resources extraction illustrates how human activities and regional insecurity are hampering biodiversity research and conservation. Although there are still numerous knowledge gaps for the optimised conservation of biodiversity in the region, a set of research priorities is provided to identify the framework data needed to support regional conservation planning.
Abstract
Knowing the causes of biological invasion success can be relevant to combat future invasive processes. The recent invasion of the horseshoe whip snake Hemorrhois hippocrepis on the island of ...Ibiza provides the opportunity to compare natural history traits between invasive and source populations, and to unravel what makes this snake a successful invader that is threatening the only endemic vertebrate of the island, Podarcis pityusensis. This study compares the basic reproductive traits of mainland native and invasive populations of the snake. Our results revealed that invasive populations were characterized by female maturity at a smaller size, extended reproductive period, and much lower reproduction frequency compared to the native population. In contrast, some major reproductive traits—the abdominal fat body cycle, clutch size, hatchling body size, and hatchling body condition, did not differ between the two populations. Some of these results must reflect the environmental differences in the recently invaded island with respect to the source area, and overall plasticity of reproductive traits. Plasticity is evolutionarily interesting, and may aid the successful growth of this species in their invasiveness of Mediterranean islands like Ibiza. The most significant finding is that this expression of phenotypic plasticity occurred rapidly in this invasive population, within a period of 14 years maximum. Our results on the reproduction ecology of the invasive population were not conclusive regarding the factors determining the invasiveness of the snake and pointed to alternative causes.
The effects of climate change on organisms are now being extensively studied in many different taxa. However, the variation in body size, usually shrinkage in response to increasing temperature, has ...received little attention regarding to reptiles. During past periods of global warming, many organisms shrank in size, and current evidence and experiments manipulating temperature have shown a biomass decrease in some organisms with increasing temperatures. Here we test whether the body size of the Montpellier snake Malpolon rnonspessulanus from the southeastern Iberian Peninsula is changing and correlated with the increasing temperature in this region during a 39- year period （1976-2014）. We measured the snout-vent length （SVL） of vouchers in scientific collections to check for trends in adult body size at the population level in relation with temperature, while controlling for the age of the individuals （estimated by skeletochronology, n =141）. Given the great ontogenetic variation in body size of the study species, we categorized age in 3 classes： ＂young adults＂ （under 5 years old）, ＂intermediate adults＂ （from 5 to 7 years old）, and ＂old adults＂ （from 8 to 14 years old）. By means of linear mixed models, we found a negative relationship between SVL of ＂old adults＂ and average annual temperature in the region during the lifetime of each individual. Our results indicate that largest and oldest individuals of the Montpellier Snake, that is, males because of strong sexual size dimorphism in this species, disappeared from the study population, and suggest that it occurred in response to rising environmental temperature.
In the diet of raptors the presence of prey-species is influenced by their abundance and the ground-level vegetation in territories, this situation being analysed for the Bonelli’s eagle (
Hieraaetus ...fasciatus) in south-eastern Spain. First, the minimum number of prey-items for the reliability of results was tested, obtaining between 15 and 30 prey-items depending of pair. Second, differences in prey frequency and productivity among pairs was analysed, finding an interpair shift in both variables, but there was no relationship between the frequency of prey-species in the diet and productivity. Third, it was found that the percentage of European wild rabbit in the diet was less correlated with its abundance in territories than with the surface of open land in the same. This suggests that accessibility to rabbits would be more important for the Bonelli’s eagle that the absolute abundance of this prey type. Thus, open land is the single variable selected by a multiple multiple-regression analysis explaining the frequency of rabbits in this raptor’s diet. Birds as prey complemented the diet when open-land scarcity in the territories implies low rabbit detectability and consumption. Conservation measures proposed concerning the increase of prey availability in this declining population should consider both the absolute prey density and prey detectability, avoiding extensive reforestation in territories and favouring vegetation structure suitable for prey detection by eagles.
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