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Artificial light at night (ALAN) is expanding worldwide. Many physiological effects have been reported in animals, but we still know little about the consequences for the visual system. The pupil contributes to control incoming light onto the retina. Sudden increases in light intensity evokes the pupil light reflex (PLR). Intrinsically photosensitive retinal ganglion cells (ipRGC) affect PLR and melatonin expression, which largely regulate circadian rhythms and PLR itself. IpRCG receive inputs from various photoreptors with different peak sensitivities implying that PLR could be altered by a broad range of light sources. We predicted ALAN to enhance PLR. Contrary to our prediction, dark‐adapted cane toads Rhinella marina, exposed to ALAN (5 lx) for 12 days, exhibited a lower PLR than controls and individuals exposed to 0.04 lx, even after 1 h in bright light. We cannot conclude whether ALAN induced a larger pupil size in dark‐adapted toads or a slower initial contraction. Nevertheless, the response was triggered by a light source with an emission peak (590 nm) well above the sensitivity peak of melanopsin, the main photoreceptor involved in PLR. Therefore, ALAN alters the capacity of toads to regulate the incoming light in the eye at night, which may reduce the performance of visually guided behaviors, and increase mortality by predators or road kills at night. This first study emphasizes the need to focus on the effect of ALAN on the vision of nocturnal organisms to better understand how this sensory system is altered and anticipate the consequences for organisms. [ABSTRACT FROM AUTHOR]

Phenotypic variations between populations often correlate with climatic variables. Determining the presence of phenotypic plasticity and local adaptation of a species to different environments over a large spatial scale can provide insight on the persistence of a species across its range. Amphibians, and in particular their larvae, are good models for studies of phenotypic variation as they are especially sensitive to their immediate environment. Few studies have attempted to determine the mechanisms that drive phenotypic variation between populations of a single amphibian species over a large spatial scale especially across contrasting climatic regimes. The African clawed frog, Xenopus laevis, occurs in two regions with contrasting rainfall regimes in southern Africa. We hypothesised that the phenotypic variation of life-history traits of X. laevis tadpoles emerges from a combination of plastic and genetic responses. We predicted that plasticity would allow the development of tadpoles from both regions in each environment. We also predicted that local adaptation of larval traits would drive the differentiation of reaction norms between populations and lower survival in tadpoles reared away from their home environment. We measured growth, time to metamorphosis, and survival in a reciprocal transplant experiment using outdoor mesocosms. Supporting our prediction, we found that the measured variation of all traits was explained by both adaptation and plasticity. However, the reaction norms differed between populations suggesting adaptive and asymmetric plasticity. All tadpoles experienced lower survival when translocated, but only translocated tadpoles from the winter rainfall region matched survival of local tadpoles. This has implications for the dynamics of translocated X. laevis into novel environments, especially from the winter rainfall region. Our discovery of their asymmetric capacity to overcome novel environmental conditions by phenotypic plasticity alone provides insight into their invasion success. [ABSTRACT FROM AUTHOR]

Aquatic anuran species are difficult to detect and observe and this is a major limit to the study of their behaviour and ecology. This habit limits the direct monitoring of sexual and foraging activity, and the investigation of how environmental factors influence their expression as well as how individuals allocate time between competing activities. We investigated this issue in Xenopus laevis , a mostly aquatic frog that forages and emits calls underwater. This model species in biology has been extensively studied in the lab but its behaviour in nature remains poorly described. We carried out a study in a pond during the breeding season in the French invasive range. We recorded underwater vocal activity as a proxy for sexual activity using a hydrophone, set food-baited traps to quantify foraging activity, and recorded environmental conditions (moonlight intensity, temperature and rainfall) over two lunar cycles. We found that individuals engage in these two activities during the breeding season. At the peak of the breeding period, vocal activity was expressed during the day. The investment in reproduction (calling activity) may reduce the time allocated to foraging on a circadian scale. The two activities seem to be partitioned depending on moonlight intensity, with a stronger effect on males. Foraging activity decreased and vocal activity increased when moonlight intensity increased. We also observed a negative effect of temperature and a positive effect of rainfall on vocal activity only. Our method is promising to monitor the activity of other aquatic anurans. [ABSTRACT FROM AUTHOR]

Photoperiod is a major factor regulating biological rhythms in animals and plants. At low latitudes, annual variation in daylength is low and species are expected to strongly rely on photic cues to reset their circadian clocks. A corollary is that individuals should be strongly affected by sudden changes in the photic regime as those generated by artificial light at night (ALAN). We tested this hypothesis in an anuran in Costa Rica (10°N). Using an outdoor experimental design, we exposed adult cane toads Rhinella marina, a broadly distributed tropical anuran species to two ALAN intensities (0.04 and 5 lx). Locomotor activity was reduced at the lowest intensity, and the activity pattern shifted from crepuscular to nocturnal. Contrary to humans and mice in which ALAN favor obesity, toads from the two exposed groups did not gain mass whereas controls did. Corticosterone was reduced at the highest intensity, a possible consequence of the reduced activity of toads or the altered regulation of their circadian pattern. Thus, the behavioral and physiological disruption that we observed supports the hypothesis of the strong reliance on photic cues to regulate circadian rhythms and control homeostasis in this intertropical anuran. Furthermore, our results suggest that the negative effects of ALAN on physiology, in particular body mass regulation, may differ between vertebrate groups, thus preventing anticipated generalization before more comparative studies have been carried out. We stress the importance of considering the impact of the changing nocturnal environment in the intertropical zone which host the largest fraction of biodiversity. Light pollution should more strongly affect animals at low latitudes because day length is stable year round. In Costa Rica, cane toads exposed to light at night in outdoor boxes moved less, failed to gain mass, and their corsticosterone levels dropped. Even in a species frequently occurring near human settlements strong behavioral and physiological disruption are observed, which suggests that particular attention should be paid to the effects of light pollution on animals in the intertropical zone. [ABSTRACT FROM AUTHOR]

Generalist invasive predators consume prey at different trophic levels and generate drastic changes in local communities. However, the long-term effects of predation may be reduced by eco-evolutionary responses of native populations. The capacity of prey species distributed across the trophic network to develop antipredator responses may determine the ecosystem potential to buffer against the invader. The African clawed frog is a major invader on several continents. Because of its large size, generalist diet, and aquatic lifestyle, we predicted the development of antipredator responses in prey species at different trophic levels. We tested for behavioral shifts between populations within and outside the invasive range in the herbivorous snail Physella acuta and the predatory heteropteran, the backswimmer Notonecta glauca. We detected antipredator responses in both prey species. In sympatry, P. acuta stayed higher in the water column, while N. glauca spent more time swimming underwater and less time surfacing when the predator cues were present. In allopatry, P. acuta dived deeper and N. glauca spent more time surfacing and stayed longer still underwater. In both species, sympatric populations showed evidence of olfactory recognition of the frog. Our results show that the introduction of a top predator like Xenopus laevis in the pond ecosystem drives behavioral antipredator responses in species across the trophic network. Eco-evolutionary processes may allow some degree of long-term resilience of pond communities to the invasion of X. laevis. [ABSTRACT FROM AUTHOR]

Aim: Exposure to artificial light at night (ALAN) is a risk factor for organisms. Considering the spread and increasing intensity of night brightness across the globe, and the key role of light at all biological levels, alterations of ecosystems are expected. Yet, we cannot predict the severity of the effects of ALAN in several biomes because little information is available outside the temperate zone. We reviewed current knowledge and identified traits that could be targeted to fill this knowledge gap in order to contribute to the elaboration of a biogeographical framework for the study of ALAN at the global scale. Location: Global. Time period: Current and next decades. Methods: We analysed the latitudinal variation in ALAN and focused on environmental factors that vary with latitude but that have been overlooked. We reviewed biological traits that exhibit latitudinal variation and depend on light and photoperiod and compiled information about the predicted changes in human demography and road networks across different world regions. Results: Cloud cover amplifies ALAN far away from urbanized areas. Because of the higher frequency of overcast sky nights, exposure effects may be stronger both at high latitudes and across a large fraction of the intertropical zone, although at different times of the year. Intertropical biomes host the largest fraction of global biodiversity. Although currently they are not the most exposed to ALAN, their human populations are growing, and urbanized areas and road networks are expanding. Hence, ALAN could have strong ecological consequences, with cloud cover as an aggravating factor. Perspectives: Knowledge gaps currently limit our ability to predict the effects of ALAN in different biomes. Therefore, it will be important to start investigating the consequences of this novel environmental factor across the globe, in order to develop a relevant theoretical framework. [ABSTRACT FROM AUTHOR]

As invasive species are one of the principal threats on global biodiversity, assessing their impact is a crucial element of conservation biology. Quantifying the possible impacts of an invasive population represents the first step in the establishment of efficient management plans. In this study, we applied a method of site-occupancy modeling to estimate the influence of an invasive frog, Xenopus laevis, on the amphibian species richness in western France. In our analyses we took into account habitat characteristics (i.e. the size and general shape of the ponds), the structure of the aquatic vegetation, the presence of other vertebrates, and the physicochemical parameters of the pond. Richness was negatively related to the abundance of X. laevis and to the time since colonization as estimated by the distance of the pond to the site of introduction. Habitat niche breadth of native amphibians did not differ between invaded and non-invaded areas. This might be a consequence of the homogeneity of the habitats selected for our study. The lack of heterogeneity in the abiotic factors, the absence of a correlation between species richness and these abiotic factors, and the correlation of the abundance and time since colonization by X. laevis with species richness suggest a negative effect of this species on local amphibians. This result highlights the importance of conservation and management plans aiming to limit the expansion of this invasive species. [ABSTRACT FROM AUTHOR]

Artificial light at night (ALAN) is an increasing phenomenon worldwide. It causes a wealth of biological and ecological effects that may eventually affect populations and ecosystems. Despite the growing concern about ALAN, little is known about the light levels species are exposed to at night, especially for wetlands and underwater habitats. We determined nocturnal irradiance in urban and peri-urban wetlands above and under water, and assessed the effect of cloud cover on the variability of ALAN across the urban gradient. Even in aquatic habitats, cloud cover could increase irradiance beyond values observed during clear full moon nights. We report a negative relationship between baseline irradiance and the increase in irradiance during overcast nights. According to this result and previous studies, we propose that the change in the variation regime of ALAN between the urban center and rural land at its periphery is a usual feature. We discuss the ecological and evolutionary implications of this spatial variation in the urban and peri-urban environment. [ABSTRACT FROM AUTHOR]

Predicting the magnitude and nature of changes in a species' range is becoming ever more important as an increasing number of species are faced with habitat changes or are introduced to areas outside of the species' native range. An organism's investment in life-history traits is expected to change during range shifts or range expansion because populations encounter new ecological conditions. While simulation studies predict that dispersal and reproductive allocation should increase at the range edge, we suggest that reproductive allocation might decrease at the range edge due to energy allocation trade-offs. We studied the reproductive investment of an invasive amphibian, Xenopus laevis, and measured reproductive allocation in three clusters of populations distributed from the centre to the edge of the colonized range of X. laevis in France. Resource allocation was estimated with the scaled mass index of gonads of both sexes during the local period of reproduction of the species. The level of resources allocated to reproduction was lower at the periphery of the colonized range compared to the centre and may be the result of changes in tradeoffs between life-history traits. Such a pattern could be explained by interspecific competition or enhanced investment in dispersal capacity. [ABSTRACT FROM AUTHOR]

Disentangling the factors shaping species distributions remains a central goal in biogeography, ecology and evolutionary biology. The extrinsic pressures that may facilitate range shifts, such as climatic factors or biotic interactions are well known. However, in contrast, the possible intrinsic factors are manifold and hard to generalize across taxa. Recently, several theoretical studies have investigated the consequences of moving range borders on genetic diversity. However, empirical studies that support or refute these theoretical predictions are scarce. Moving contact zones between parapatric sister species are suitable models to test these hypotheses. Changes in genetic diversity can be tested simultaneously along the expanding and receding edges of two species of the contact zone while accounting for intra-specific effects (e.g. introgression). The two Old World warblers Hippolais polyglotta and H. icterina form a narrow moving contact zone, where interspecific interactions are suspected to be the main factor shaping this zone. We investigated the population genetic structure of both species along a transect ranging from the core range of the expanding H. polyglotta across the contact zone and far into the range of the receding H. icterina. The theoretical predictions of changes in genetic diversity at the range edges were tested. No gradual change in genetic diversity was detected for both the expanding and the receding range margin. Furthermore, no genetic structure was found in either species supporting the hypothesis that long distance dispersal (LDD) occurs frequently due to the high mobility of these long-distance migrants. The results suggest that when dispersal propensity is high and accompanied by frequent LDD events, then neither an enrichment nor a depletion of alleles along moving range edges would be detected. This these species as the probability to retain genetic diversity during exogenous induced range shifts is high in such mobile species. [ABSTRACT FROM AUTHOR]

Detection is crucial in the study and control of invasive species but it may be limited by methodological issues. In amphibians, classical survey techniques exhibit variable detection probability depending on species and are often constrained by climatic conditions often requiring several site visits. Furthermore, detection may be reduced at low density because probability capture (passive traps), or activity (acoustic surveys) drop. Such limits may impair the study of invasive species because low density is typical of the onset of colonisation on a site. In the last few years, environmental DNA (eDNA) methods have proved their ability to detect the presence of aquatic species. We developed here an eDNA method to detect Xenopus laevis in ponds. This austral African species is now present worldwide because of its use in biology and as a pet. Populations have settled and expanded on several continents so that it is now considered as one of the major invasive amphibians in the World. We detected the presence of X. laevis at density as low as 1 ind/100 m2 and found a positive relationship between density in ponds and rate of DNA amplification. Results show that eDNA can be successfully applied to survey invasive populations of X. laevis even at low density in order to confirm suspected cases of introduction, delimit the expansion of a colonized range, or monitor the efficiency of a control program. [ABSTRACT FROM AUTHOR]

Remotely sensed data are frequently employed for monitoring vegetation and for estimating herbivore diversity. Their use for predicting predator arthropod species abundance and richness has also been investigated with success for ants and beetles in forests using normalised difference vegetation index ( NDVI) and for beetles in mountain forests using light detection and ranging data., We investigated whether vegetation indices, derived from multispectral SPOT imagery could predict abundance and species richness of ground active spiders and ground beetles in a new ecological context, the floodplain meadows of the Loire River in Western Europe. Using pitfall traps, we collected carabids and spiders in the field., Maximum vegetation height, litter-depth and plant species richness best explained species assemblages of both groups (multivariate analyses). NDVI and enhanced vegetation index ( EVI 2) were strongly related to activity-density and species richness for ground beetles only, EVI 2 being the best surrogate. Relationships between vegetation indices and spider assemblage patterns were either non-significant or weak., We demonstrated that EVI 2 is a good surrogate of the abundance and richness of carabid species in a temperate floodplain, and has potential as a low cost method for mapping arthropod assemblages at large spatial scales., Our approach provides a tool which contributes to biodiversity assessment at large spatial scales. It can also contribute to the prioritisation of conservation areas and early change detection, as carabids are keystone indicators. [ABSTRACT FROM AUTHOR]

Microsatellites are a valuable tool in the analysis of population genetic structure. Utilising microsatellite markers that were originally isolated from other species (cross-species amplification) can prove an efficient way, in terms of time and cost, to obtain markers for genetic studies. Here, 55 avian microsatellite primer pairs were tested for the cross-amplification in the Melodious Warbler (Hippolais polyglotta). Thirty-five markers amplified, of which 22 were polymorphic, displaying two to nine alleles in the 15 individuals genotyped. The 35 markers which amplified in the Melodious Warbler were tested in its sister species the Icterine Warbler (H. icterina). Twenty-four markers were amplified, 14 of which were polymorphic in the five H. icterina individuals genotyped. Thirteen loci were polymorphic in both species. The polymorphic loci identified are suitable for analysing the genetic population structure and assigning parentage. [ABSTRACT FROM AUTHOR]

Background: Functional communication in the UV range has been reported in Invertebrates and all major groups of Vertebrates but Amphibians. Although perception in this wavelength range has been shown in a few species, UV signalling has not been demonstrated in this group. One reason may be that in lentic freshwater habitats, litter decomposition generates dissolved organic carbon that absorbs UV radiation and thus hinders its use for visual signalling. We tested the effect of male UV characteristics on female sexual preference in two newt species that experience contrasting levels of UV water transmission when breeding. Methodology/Principal Findings: We analysed water spectral characteristics of a sample of breeding ponds in both species. We quantified male ventral coloration and measured male attractiveness under two lighting conditions (UV present, UV absent) using a no-choice female preference design. UV transmission was higher in Lissotriton vulgaris breeding sites. Male UV patterns also differed between experimental males of the two species. We observed a first common peak around 333 nm, higher in L. vulgaris, and a second peak around 397 nm, more frequent and higher in L. helveticus. Male attractiveness was significantly reduced in L. vulgaris when UV was not available but not in L. helveticus. Male attractiveness depended on the hue of the first UV peak in L. vulgaris. Conclusion/Significance: Our study is the first report of functional UV-based communication in Amphibians. Interestingly, male spectral characteristics and female preferences were consistent with the differences in habitat observed between the two species as L. helveticus often breeds in ponds containing more UV blocking compounds. We discuss the three hypotheses proposed so far for UV signalling in animals (enhanced signal detectability, private communication channel, indicator of individual quality). [ABSTRACT FROM AUTHOR]

1. The occurrence of endocrine disruption is increasing and may now affect most, if not all, ecosystems. Owing to its impact on survival and reproduction, it is increasingly important to consider this factor in ecological studies. The study of secondary sexual traits is of particular interest because they are under strong hormonal control and play a crucial role in mating. A neglected sub-lethal effect of endocrine disruption is the reduction of male attractiveness, and the distortion of the sexual selection process. 2. Nitrate is one of the most widespread endocrine disruptors because of its extensive use in agriculture. Studies, especially in amphibians, have mostly focused on early developmental stages, probably because these were considered critical for population dynamics. However, negative effects on adult survival or reproductive success may also affect population demography. 3. We surveyed nitrate concentration in a large sample of ponds. We then exposed male palmate newts, Triturus helveticus, to high (75 mg L−1) but realistic concentration of sodium nitrate to investigate the effect of nitrate on the expression of secondary sexual traits and male attractiveness. 4. Exposure to nitrate for 3 weeks was found to limit the expression of sexual traits and to reduce body growth; exposure for 10 days reduced male attractiveness. Female preferred males unexposed to nitrate in olfactory tests but not in visual tests. 5. The expression of secondary sexual characteristics and body size is reduced in males exposed to realistic nitrate concentration. However, a drop in male attractiveness may first be caused by disruption of the production of olfactory cues. Depending on the frequency of contaminated breeding sites, the disruption of male ability to express sexual signals might affect the sexual selection process in palmate newts and eventually reduce population reproductive output. We discuss the ecological and evolutionary implications of this result. [ABSTRACT FROM AUTHOR]

Abstract: Reproductive character displacement is commonly described as larger phenotypic differences between species living in sympatry rather than in allopatry. We investigated this phenomenon on two amphibians found in their contact zone where syntopic and allotopic sites alternate. To test the effect of syntopy with Lissotriton vulgaris on the Lissotriton helveticus phenotype, we studied the morphology of adult males and females while controlling for environmental factors (i.e. land use and flood risk). Using linear mixed-effects models, we found that females of L. helveticus expressed a deeper tail when in the presence of the other species, a pattern consistent with reproductive character displacement. This pattern has been rarely observed in Amphibians. It suggests that male newts incur large mating costs when selecting heterospecific partners. Our study also emphasizes that the evolution of mate recognition systems could occur at a microgeographical scale within a sympatric area. To cite this article: A. Johanet et al., C. R. Biologies 332 (2009). [Copyright &y& Elsevier]

In theory, animal signals are designed to optimize transmission across a specific habitat. However, sexual signals characteristics often reflect habitat quality, a feature that does not necessarily match habitat structure. Besides, many species exploit a particular habitat for breeding so that the growth of sexual signals can depend on the additive effects of breeding and non-breeding habitats. We combined field and experimental data to investigate the relative effect of terrestrial and aquatic habitat on the development of sexual ornaments in the palmate newt, Triturus helveticus. This species exploits a large ecological range of habitats. Like many amphibians, it spends the breeding season in water and the rest of year on land. We tested the influence of terrestrial (forest cover) and aquatic habitat variables (turbidity, organic matter, pH, nitrate and chloride) on male sexual morphology. Neither terrestrial nor aquatic habitat variables accounted for body size variation. In contrast, the size of male sexual traits decreased with water turbidity, suggesting that the expression of visual signals matched the local conditions of signal transmission. We provide experimental evidence that this pattern is not caused by reduced foraging efficiency in turbid water. We propose alternative mechanisms to account for the relationship between turbidity and visual sexual signals, and discuss the consequences of small scale environmental variation on mate choice. [ABSTRACT FROM AUTHOR]

An increasing number of studies describe moving hybrid zones. This raises the issue of their actual frequency and emphasizes the need for methods that enable the detection of zone movements without historical records. Asymmetric introgression, usually considered as a signature of geographical shift, might be misleading when applied to mitochondrial or potentially non-neutral markers. We investigated mitochondrial and genomic introgression, using 30 AFLP derived markers, in a well-documented moving avian contact zone between two warblers. We found no instances of cross-species transmission of mitochondrial DNA but we detected nuclear introgression. Introgression levels were higher in the expanding species. Highest introgression was observed in populations that recently became allopatric than in current sympatric populations, which suggests that alien genetic material mainly spread at the time just before the receding species became extinct. We propose that either local recruitment or positive selection on some loci contribute to this pattern. Furthermore, we propose that, when the rarefaction of sexual partners drive the hybridization process, movement could be revealed by introgression peaking on the rear edge of the moving zone, or in its close vicinity. [ABSTRACT FROM AUTHOR]

Although chemosignals are largely used in sexual communication in urodeles, olfactometer studies in newts provided contrasting results about the sex specificity of female behavioural responses. Because long-range sexual advertisement is believed to be costly, some species might restrain this activity to close interactions with conspecifics. We tested chemical-mediated sexual attraction in female palmate newt ( Triturus helveticus) by measuring the attraction to male and female odours in a linear water olfactometer. Unexpectedly, females were attracted towards conspecifics regardless of sex. They did not show attraction towards Limnaea stagnalis, a common sympatric aquatic gastropod. These results do not support the use of long-range male sexual signalling in the palmate newt. Instead, conspecific attraction is likely to promote aggregation of males and females in breeding ponds. Observations in the field and in the laboratory tend to support the aggregative behaviour of this species. We discuss the possible function of conspecific attraction in this context. Heading towards any conspecific would increase the probability of finding potential mates. Chemical cues do not need to be sex-specific at that stage so that long-range sexual advertisement might be unnecessary. This work emphasizes the need for studies investigating the evolutionary relationships between sexual signalling systems and population-distribution patterns. [ABSTRACT FROM AUTHOR]

Birdsong is one of the main models in sexual selection studies. Most investigations focused on oscines in which male song and female preference learning occur. Yet, some non-oscines are well suited for such studies as well. In Columbidae song learning does not occur. However, like in oscines, song is involved in inter- and intra-sexual interactions. Surprisingly, experimental evidence of female song-based preferences are still largely lacking in this group. We conducted playback tests on wild-caught Streptopelia decaocto females. We tested for the sexual function of song by playing decaocto songs versus songs of an unrelated species. We then investigated female responses to trill. Although they do not produce this trait, males react more strongly to artificially trilled decaocto songs, i.e. to conspecific songs in which a trill from a S. roseogrisea song has been inserted, than to normal decaocto songs. We also tested female responses to S. roseogrisea songs. Females flew more often and with a shorter latency during decaocto songs than during wren songs, suggesting that species recognition occurred, but we found no evidence of preference for trilled decaocto songs. The low activity observed during the experiment might have obscured actual preferences. Nevertheless, females consistently reacted more to normal decaocto songs than to trilled decaocto or roseogrisea songs. This contrasts with the strong responses for trilled decaocto songs and the virtual lack of reaction to S. roseogrisea songs observed in males. Thus, female collared doves, as receivers, may have different characteristics from males and impose constraints on the evolution of song. [ABSTRACT FROM AUTHOR]

MtDNA barcoding is regularly applied to determine the provenance of invasive species. Variation in spatial genetic structuring across a species’ range, typically high within glacial refugia and low in postglacially colonized areas, influences the precision of this approach. The palmate newt (Lissotriton helveticus) has been introduced north of its native range inside the Netherlands. We conduct mtDNA barcoding to try and retrace the origin of the introduced localities. A large increase in sample size, particularly focusing on temperate Europe, emphasizes that the palmate newt shows practically no genetic variation outside the Iberian Peninsula glacial refugium. While we find a haplotype previously only known from the Iberian Peninsula inside the native range in Belgium, the haplotype present in the introduced Dutch populations occurs widely throughout the native range north of the Iberian Peninsula. Although mtDNA barcoding can be a powerful tool in invasion biology, the palmate newt case exposes its limitations. [ABSTRACT FROM AUTHOR]

Focuses on the morphological variation and evolution of wing length in the Icterine Warbler. Characteristics of Icterine Warbler; Breeding behavior of the species.

The description of functional connectivity is based on the quantification of landscape resistance, which represents species‐specific movement costs across landscape features. Connectivity models use these costs to identify movement corridors at both individual and population levels and provide management recommendations for populations of conservation interest. Typically, resistance costs assigned to specific land cover types are assumed to be valid for all individuals of the population. Little attention has been paid to intraspecific variation in resistance costs due to age or dispersal syndrome, which may significantly affect model predictions.We quantified resistance costs in an expanding invasive population of the African clawed frog Xenopus laevis in Western France. In this principally aquatic amphibian, juveniles, sub‐adults and adults disperse overland. The enhancement of dispersal traits via spatial sorting has been also observed at the range periphery of the population. Resistance costs, and thus connectivity, might vary as a function of life stage and position within the invaded range.We assessed multiple dimensions of functional connectivity. On various land cover types, we measured locomotion, as crossing speed, in different post‐metamorphic age classes, and dehydration, sensitivity of locomotion to dehydration and substrate preference in juveniles. We also tested the effect of the position in the invaded range (core vs. periphery) on individual performances.In juveniles, general trends towards higher resistance costs on grass and lower resistance costs on bare soil and asphalt were observed, although not all experiments provided the same cost configurations. Resistance to locomotion varied between age classes, with adults and sub‐adults facing lower costs than juveniles, particularly when crossing structurally complex land cover types such as grass and leaf litter. The position in the range had a minor effect on landscape resistance, and only in the dehydration experiment, where water loss in juveniles was lower at the range periphery.Depicting functional connectivity requires (a) assessing multiple dimensions of behavioural and physiological challenges faced by animals during movement; (b) considering factors, such as age and dispersal syndrome, that may affect movement at both individual and population levels. Ignoring this complexity might generate unreliable connectivity models and provide unsupported management recommendations for conservation. [ABSTRACT FROM AUTHOR]

The worldwide expansion of artificial light at night (ALAN) is acknowledged as a threat to biodiversity through alterations of the natural photoperiod triggering the disruption of physiological functions. In vertebrates, melatonin production during the dark phase can be decreased or suppressed by nocturnal light as shown in many taxa. But the effect of ALAN at low intensity mimicking light pollution in peri-urban area has never been investigated in amphibians. We filled this gap by studying the impact of low ALAN levels on the expression of genes related to melatonin synthesis and signaling in two anurans (agile frog, Rana dalmatina, and common toad, Bufo bufo). Circadian expression of genes encoding enzymes catalyzing melatonin synthesis (aralkylamine N -acetyltransferase, AANAT and acetylserotonin O -methyltransferase, ASMT) or melatonin receptors (Mel1a, Mel1b and Mel1c) was investigated using RT-qPCR after 23 days of nocturnal exposure to control (< 0.01 lx) or low ALAN (3 lx). We showed that the relative abundance of most transcripts was low in late afternoon and early evening (06 pm and 08 pm) and increased throughout the night in R. dalmatina. However, a clear and ample nocturnal pattern of target gene expression was not detected in control tadpoles of both species. Surprisingly, a low ALAN level had little influence on the relative expression of most melatonin-related genes. Only Mel1c expression in R. dalmatina and Mel1b expression in B. bufo were affected by ALAN. This target gene approach provides experimental evidence that melatonin signaling pathway was slightly affected by low ALAN level in anuran tadpoles. [Display omitted] • Melatonin-related gene expression tested at night under 2 light levels in 2 anurans. • Gene analysis based on respective species transcriptome and valid reference genes. • Preliminary description of a nocturnal rhythm in gene expression in tadpoles. • In both species, light pollution did not affect melatonin synthesis at gene level. • Melatonin signaling was slightly altered by light pollution during the night. [ABSTRACT FROM AUTHOR]

Abstract: Aim: Species distribution modelling, a family of statistical methods that predicts species distributions from a set of occurrences and environmental predictors, is now routinely applied in many macroecological studies. However, the reliability of evaluation metrics usually employed to validate these models remains questioned. Moreover, the emergence of online databases of environmental variables with global coverage, especially climatic, has favoured the use of the same set of standard predictors. Unfortunately, the selection of variables is too rarely based on a careful examination of the species' ecology. In this context, our aim was to highlight the importance of selecting ad hoc variables in species distribution models, and to assess the ability of classical evaluation statistics to identify models with no biological realism. Innovation: First, we reviewed the current practices in the field of species distribution modelling in terms of variable selection and model evaluation. Then, we computed distribution models of 509 European species using pseudo‐predictors derived from paintings or using a real set of climatic and topographic predictors. We calculated model performance based on the area under the receiver operating curve (AUC) and true skill statistics (TSS), partitioning occurrences into training and test data with different levels of spatial independence. Most models computed from pseudo‐predictors were classified as good and sometimes were even better evaluated than models computed using real environmental variables. However, on average they were better discriminated when the partitioning of occurrences allowed testing for model transferability. Main conclusions: These findings confirm the crucial importance of variable selection and the inability of current evaluation metrics to assess the biological significance of distribution models. We recommend that researchers carefully select variables according to the species' ecology and evaluate models only according to their capacity to be transfered in distant areas. Nevertheless, statistics of model evaluations must still be interpreted with great caution. [ABSTRACT FROM AUTHOR]

The concept of umbrella species assumes that concentrating resources on the protection of a single species contributes to the conservation of a suite of species and ecological processes belonging to the same ecosystem. The environmental requirements and geographical distribution of the umbrella species should thus overlap those of the group of targeted species. In western France, the conservation of several large grassland floodplains relies on agri-environmental schemes targeting one single bird species, the corncrake Crex crex. It is considered as an umbrella species but no real assessment of its effectiveness has been carried out so far. We used a two-step methodology to assess the potential of the corncrake to act as an umbrella species by estimating niche overlap in the environmental and geographic space between the main ground-nesting species of the bird community in these grasslands, including the corncrake and four passerines. The five species showed substantial differences in their ecological niches so that their distributions did not perfectly overlap. Overlaps in predicted distributions between pairs of species depended on the threshold used to convert suitability to binary maps. Moreover, the number of species that could be protected by a candidate umbrella species was affected by the overlap criterion of success. Although the corncrake may be used as an umbrella species, it would be outperformed by several passerine species. Our study highlights the potential of using niche overlap to select umbrella species. It also reveals the importance of analysing the sensitivity of outputs when changing thresholds and overlap criteria. [ABSTRACT FROM AUTHOR]

Forecasting the colonization process is important for wildlife managers who supervise the reintroduction of endangered species or control the spread of invasive species. Patch connectivity is thus critical to predicting the fates of expanding populations. Connectivity in river networks results from river dendritic structure and dispersal modality of organisms. Both factors may strongly affect the colonization process and the efficiency of conservation action plans. Based on empirical data, we simulated, using a simplified model with limited number of parameters, the colonization of a large river network, the Loire River, by the native Eurasian beaver and the invasive African clawed frog. For each species, we inferred model parameters (dispersal behavior and distances) by comparing the simulated and the observed distributions. Using network theory, we evaluated the efficiency of alternative conservation strategies to prevent or promote colonization of the river network. Network robustness to fragmentation and disturbance was also assessed. The model accurately predicted > 70% of the observed species ranges. Conservation strategies that selectively protect habitat patches with the highest connectivity values provide a weak advantage at preventing connectivity loss compared to random protection strategies. In contrast, the targeted destruction of highly connected patches had a much stronger effect on the fragmentation of the network than the random removal of habitat patches. Spatial network topology strongly contributes to determining colonization patterns of large river watersheds. Network theory allows tests for robustness of rivers to fragmentation and disturbance, and identification of strategies for conservation planning. [ABSTRACT FROM AUTHOR]

By altering or eliminating delicate ecological relationships, non-indigenous species are considered a major threat to biodiversity, as well as a driver of environmental change. Global climate change affects ecosystems and ecological communities, leading to changes in the phenology, geographic ranges, or population abundance of several species. Thus, predicting the impacts of global climate change on the current and future distribution of invasive species is an important subject in macroecological studies. The African clawed frog (Xenopus laevis), native to South Africa, possesses a strong invasion potential and populations have become established in numerous countries across four continents. The global invasion potential of X. laevis was assessed using correlative species distribution models (SDMs). SDMs were computed based on a comprehensive set of occurrence records covering South Africa, North America, South America and Europe and a set of nine environmental predictors. Models were built using both a maximum entropy model and an ensemble approach integrating eight algorithms. The future occurrence probabilities for X. laevis were subsequently computed using bioclimatic variables for 2070 following four different IPCC scenarios. Despite minor differences between the statistical approaches, both SDMs predict the future potential distribution of X. laevis, on a global scale, to decrease across all climate change scenarios. On a continental scale, both SDMs predict decreasing potential distributions in the species’ native range in South Africa, as well as in the invaded areas in North and South America, and in Australia where the species has not been introduced. In contrast, both SDMs predict the potential range size to expand in Europe. Our results suggest that all probability classes will be equally affected by climate change. New regional conditions may promote new invasions or the spread of established invasive populations, especially in France and Great Britain. [ABSTRACT FROM AUTHOR]

Edge avoidance is an important feature of habitat selection in grassland birds, as their density is usually reduced close to habitat boundaries. In many extensively managed European grasslands, fragmentation is caused by the presence of wooded hedgerows dividing meadows. Comparing the magnitude of hedgerow avoidance by co-occurring species is essential for the management of grassland areas and the implementation of efficient conservation schemes. We quantified hedgerow avoidance by the Corncrake and four grassland passerines in western France. As expected, all species avoided hedgerows, but the effect was less pronounced for the Corncrake. We hypothesize that this may reflect a lower predation risk towards the larger and most inconspicuous species. Alternatively, social communication in Corncrakes may be less impeded by wooded vegetation than in passerines. However, the mechanisms responsible for the observed pattern remain uncertain. Nevertheless, our study provides a general technique that can be applied to measure boundary avoidance. This information is important for policymakers in their efforts to improve management guidelines, which often do not take edge effects into account. [ABSTRACT FROM AUTHOR]

Coexistence with related species poses evolutionary challenges to which populations may react in diverse ways. When exposed to similar environments, sympatric populations of two species may adopt similar phenotypic trait values. However, selection may also favour trait divergence as a way to reduce competition for resources or mates. The characteristics of external body parts, such as coloration and external morphology, are involved to varying degrees in intraspecific signalling as well as in the adaptation to the environment and consequently may be diversely affected by interspecific interactions in sympatry. Here, we studied the effect of sympatry on various colour and morphological traits in males and females of two related newt species Lissotriton helveticus and L. vulgaris. Importantly, we did not only estimate how raw trait differences between species respond to sympatry, but also the marginal responses after controlling for environmental variation. We found that dorsal and caudal coloration converged in sympatry, likely reflecting their role in adaptation to local environments, especially concealment from predators. In contrast, aspects of male and female ventral coloration, which harbours sexual signals in both species, diverged in sympatry. This divergence may reduce opportunities for interspecific sexual interactions and the associated loss of energy, suggesting reproductive character displacement (RCD). Our study emphasizes the contrasting patterns of traits involved in different functions and calls for the need to consider this diversity in evolutionary studies. [ABSTRACT FROM AUTHOR]

The increasing use of artificial light at night has led to ecosystem exposure to light pollution worldwide. Aquatic ecosystems are particularly exposed, since lit road networks, urban development and industrial infrastructure are frequently located along river, lake, and sea shores. Although the negative effects of night‐time lighting on the physiology, behaviour, and life‐history traits of animals have been largely documented, there is a large knowledge gap about the responses of plants, especially regarding leaf functioning and resource‐management strategies. Some authors have proposed contrasting hypotheses of mechanistic responses to dim light at night in plants, but empirical results are still lacking.Based on field measurements of nocturnal irradiance in freshwater ecosystems located in peri‐urban areas, we performed a mesocosm experiment using three species of submerged aquatic plants. After 5 months of exposure to realistic dim light at night, four functional traits related to the resource management at the leaf level were measured.Artificial light at night had significant effects on the leaf physiology or chemistry, affecting their resource acquisition rate, but with different response intensities depending on the species. No effect was found on morphological or biomechanical traits for any of the studied species.These results support the hypothesis that plants could interpret dim light at night as a shaded environment and respond accordingly.We demonstrated that the effects of light at night on plants may have been underestimated in previous work. By modifying biotic interactions (e.g., competition and herbivory), these responses can have profound effects on community structure and ecosystem functioning. [ABSTRACT FROM AUTHOR]

Identifying local adaptation is crucial in conservation biology to define ecotypes and establish management guidelines. Local adaptation is often inferred from the detection of loci showing a high differentiation between populations, the so-called FST outliers. Methods of detection of loci under selection are reputed to be robust in most spatial population models. However, using simulations we showed that FST outlier tests provided a high rate of false-positives (up to 60%) in fractal environments such as river networks. Surprisingly, the number of sampled demes was correlated with parameters of population genetic structure, such as the variance of FSTs, and hence strongly influenced the rate of outliers. This unappreciated property of river networks therefore needs to be accounted for in genetic studies on adaptation and conservation of river organisms. [ABSTRACT FROM AUTHOR]

Given the status of the African clawed frog Xenopus laevis as a global amphibian invader, and the potential spread of its invasive populations in Europe and other continents, it is essential to identify the environmental factors and methods that maximize the trapping output of control actions. Cost-effective methods should maximize the number of trapped individuals, and preferably the number of females. We tested five types of attractants in traps, split into two categories: playbacks and conspecific lures, and compared their efficiency in terms of number of trapped individuals (total, females, and males) against the control method currently in use in France (use of food bait). We also estimated the influence of moonlight, an environmental factor known to affect amphibian activity. Playback methods did not increase the capture probability for either sex. In contrast, using a female as a lure allowed us to trap both more individuals (224% compared to the control), more females (186%) and more males (190%), whereas using a male only allowed us to trap more males (167%). These effects were stronger under low moonlight intensity, and at the end of the breeding season. Using female lures appeared to be the best method, both due to a higher number of trapped individuals and a higher number of trapped females. Our study also emphasizes the need for considering the influence of the lunar cycle when planning fieldwork to optimize the cost-efficiency of control actions. We recommend to preferentially set traps under low moonlight intensities. [ABSTRACT FROM AUTHOR]

One principle threat prompting the worldwide decline of amphibians is the introduction of nonindigenous amphibians. The African Clawed Frog, Xenopus laevis, is now one of the widest distributed amphibians occurring on four continents with ongoing range expansion including large parts of Europe. Species distribution models (SDMs) are essential tools to predict the invasive risk of these species. Previous efforts have focused on correlative approaches but these can be vulnerable to extrapolation errors when projecting species' distributions in nonnative ranges. Recent developments emphasise more robust process‐based models, which use physiological data like critical thermal limits and performance, or hybrid models using both approaches. Previous correlative SDMs predict different patterns in the potential future distribution of X. laevis in Europe, but it is likely that these models do not assess its full invasive potential. Based on physiological performance trials, we calculate size and temperature‐dependent response surfaces, which are scaled to geographic performance layers matching the critical thermal limits. We then use these ecophysiological performance layers in a standard correlative SDM framework to predict the potential distribution in southern Africa and Europe. Physiological performance traits (standard metabolic rate and endurance time of adult frogs) are the main drivers for the predicted distribution, while the locomotor performance (maximum velocity and distance moved in 200 ms) of adults and tadpoles have low contributions. Research Highlights: This article provides the first process‐based assessment of the potential future spread of Xenopus laevis in Europe. Compared to previously published correlative models the invasion risk may be much higher than expected. [ABSTRACT FROM AUTHOR]

Environmental DNA (eDNA) is becoming an essential tool for detecting aquatic invasive species and investigating their spread. Surprisingly, this technique has been very rarely used to investigate habitat selection, site occupancy, and colonisation despite its higher capacity to detect many species.The African clawed frog (Xenopus laevis) is a principally aquatic amphibian introduced in several continents from South Africa. In western France, no recent systematic survey of the invasion range has been attempted, mainly because of the elusive nature of the species. Furthermore, the influence of landscape features on invasion has never been investigated, even if adults and juveniles are known to disperse overland and along river networks.Using presence–absence data generated by an eDNA survey conducted across the known invasion front of X. laevis in western France, we aimed to determine whether and how the landscape features surrounding a pond influence the probability that a pond is colonised.Xenopus laevis was detected well beyond the formerly known invasive distribution and at the outward end of some transects, suggesting that we did not reach the actual invasion front in these parts of the range. The landscape variables that best predicted the presence of X. laevis in a pond were topographic wetness index and grass cover within a buffer of 250 m.Higher values of both topographic wetness index and grass cover were negatively related to the occurrence probability. The effects of these two variables more likely to reflect dispersal behaviour than habitat preferences at the pond scale.By combining the high detection probability of eDNA survey techniques and a landscape ecology approach, we may gain valuable insight into the colonisation process of water bodies by elusive invasive species. Such information is crucial to prevent access to specific sites and locate invasion front areas where connectivity can be disrupted, thus increasing the effectiveness of management countermeasures. [ABSTRACT FROM AUTHOR]

Abstract The conservation of grasslands is a concern worldwide as they are threatened by climate change and the expansion of intensive agricultural practices. The management of these areas must take into account the decisional process of habitat selection by individual organisms to identify potential ecological traps or underused habitats. Organisms that live in heterogeneous environments must select their breeding habitat based on cues that reflect habitat quality. In dynamic ecosystems such as grasslands, environmental cues used by individuals should show a strong temporal autocorrelation, such that their characteristics during breeding can be predicted earlier in the season. Our objective was to test if habitat features that explain grassland birds' distribution during the nesting and chick-rearing period could be predicted from the habitat features available on territory settlement. In western France, we analysed the relationships between the occurrence, richness and abundance of four passerine species, and vegetation structure and composition during chick-rearing period. We then analysed the temporal autocorrelation of vegetation features to determine whether the cues used during the settlement period reliably predicted the vegetation features encountered at later stages of breeding. We found that birds selected habitats characterized by a low cover of grasses, but did not respond to the physical structure of vegetation. The composition of vegetation was also the only variable that exhibited temporal autocorrelation over the course of the season, suggesting that individuals may rely on this feature to select optimal breeding habitats. Our results suggest that in dynamic environments, and in the absence of breeding experience or public information, animals can choose their breeding habitat based on a simple assessment of vegetation composition. A detailed knowledge of the underlying drivers of habitat selection is essential to manage habitats, identify potential ecological traps, and enhance the attractiveness of areas especially those under agri-environmental schemes. [ABSTRACT FROM AUTHOR]

Although of crucial importance for invasion biology and impact assessments of climate change, it remains widely unknown how species cope with and adapt to environmental conditions beyond their currently realized climatic niches (i.e., those climatic conditions existing populations are exposed to). The African clawed frog Xenopus laevis, native to southern Africa, has established numerous invasive populations on multiple continents making it a pertinent model organism to study environmental niche dynamics. In this study, we assess whether the realized niches of the invasive populations in Europe, South, and North America represent subsets of the species' realized niche in its native distributional range or if niche shifts are traceable. If shifts are traceable, we ask whether the realized niches of invasive populations still contain signatures of the niche of source populations what could indicate local adaptations. Univariate comparisons among bioclimatic conditions at native and invaded ranges revealed the invasive populations to be nested within the variable range of the native population. However, at the same time, invasive populations are well differentiated in multidimensional niche space as quantified via n-dimensional hypervolumes. The most deviant invasive population are those from Europe. Our results suggest varying degrees of realized niche shifts, which are mainly driven by temperature related variables. The crosswise projection of the hypervolumes that were trained in invaded ranges revealed the south-western Cape region as likely area of origin for all invasive populations, which is largely congruent with DNA sequence data and suggests a gradual exploration of novel climate space in invasive populations. [ABSTRACT FROM AUTHOR]

Understanding patterns of genetic structure, gene flow and diversity across a species range is required to determine the genetic status and viability of small peripheral populations. This is especially crucial in species distributed across a large range where spatial heterogeneity makes it difficult to predict the distribution of genetic diversity. Although biogeographical models provide expectations of how spatially structured genetic variation may be at the range scale, human disturbance may cause strong deviations from these theoretical predictions. In this study, we investigated genetic structure and demography at a pan-European scale in the corncrake Crex crex , a grassland bird species strongly affected by agricultural changes. We assessed population structure and genetic diversity, as well as demographic trends and direction of gene flow, in and among 15 contemporary populations of this species. Analyses revealed low genetic structure across the entire range with high levels of genetic diversity in all sites. However, we found some evidence that the westernmost populations were, to a very limited extent, differentiated from the rest of the European population. Demographic trends showed that population numbers have decreased in western Europe and remained constant across eastern Europe. Results may also indicate asymmetric gene flow from eastern to western populations. In conclusion, we suggest that the most likely scenario is that contrasting demographic regimes between eastern and western populations, driven by heterogeneous human activity, has caused not only asymmetric gene flow that has buffered small peripheral populations against genetic diversity loss, but also erased any genetic structure that may have existed. Our study not only highlights the need for coordinated action at the European scale to preserve source populations of the corncrake, but also to ensure persistence of the most threatened sites. Only by doing so will we avoid losing adaptive potential and prevent over-reliance on eastern source populations whose future may be uncertain. [ABSTRACT FROM AUTHOR]

Pathogen infections can represent a substantial threat to wild populations, especially those already limited in size. To determine how much variation in the pathogens observed among fragmented populations is caused by ecological factors, one needs to examine systems where host genetic diversity is consistent among the populations, thus controlling for any potentially confounding genetic effects. Here, we report geographic variation in haemosporidian infection among European populations of corncrake. This species now occurs in fragmented populations, but there is little genetic structure and equally high levels of genetic diversity among these populations. We observed a longitudinal gradient of prevalence from western to Eastern Europe negatively correlated with national agricultural yield, but positively correlated with corncrake census population sizes when only the most widespread lineage is considered. This likely reveals a possible impact of local agriculture intensity, which reduced host population densities in Western Europe and, potentially, insect vector abundance, thus reducing the transmission of pathogens. We conclude that in the corncrake system, where metapopulation dynamics resulted in variations in local census population sizes, but not in the genetic impoverishment of these populations, anthropogenic activity has led to a reduction in host populations and pathogen prevalence. [ABSTRACT FROM AUTHOR]

MAXENT is now a common species distribution modeling (SDM) tool used by conservation practitioners for predicting the distribution of a species from a set of records and environmental predictors. However, datasets of species occurrence used to train the model are often biased in the geographical space because of unequal sampling effort across the study area. This bias may be a source of strong inaccuracy in the resulting model and could lead to incorrect predictions. Although a number of sampling bias correction methods have been proposed, there is no consensual guideline to account for it. We compared here the performance of five methods of bias correction on three datasets of species occurrence: one “virtual” derived from a land cover map, and two actual datasets for a turtle (Chrysemys picta) and a salamander (Plethodon cylindraceus). We subjected these datasets to four types of sampling biases corresponding to potential types of empirical biases. We applied five correction methods to the biased samples and compared the outputs of distribution models to unbiased datasets to assess the overall correction performance of each method. The results revealed that the ability of methods to correct the initial sampling bias varied greatly depending on bias type, bias intensity and species. However, the simple systematic sampling of records consistently ranked among the best performing across the range of conditions tested, whereas other methods performed more poorly in most cases. The strong effect of initial conditions on correction performance highlights the need for further research to develop a step-by-step guideline to account for sampling bias. However, this method seems to be the most efficient in correcting sampling bias and should be advised in most cases. [ABSTRACT FROM AUTHOR]

Highlights: [•] We compared IUCN expert-based map of corncrake range and modelled distribution. [•] A sampling bias correction was applied to build an accurate distribution model. [•] The modelled distribution was surprisingly close to the expert-based assessment. [•] Model predictions are significantly correlated with species abundance per country. [Copyright &y& Elsevier]

Individual dispersal decisions may be affected by the internal state of the individual and the external information of its current environment. Here we estimated the influence of dispersal on survival and investigated if individual phenotype (sex and wing length) and environmental condition (conspecific density and sex-ratio) affected dispersal decisions in the banded damselfly, Calopteryx splendens. As suspected from the literature, we showed that the proportion of dispersing individuals was higher in females than in males. We also found negative-density dependent dispersal in both sexes and influence of sex-ratio on dispersal. Individuals moved less when sex-ratio was male biased. These results are consistent with a lek mating system where males aggregate in a place and hold mating territories. Contrary to our expectations, neither dispersal nor survival was affected by wing length. Nevertheless, mean adult survival was about 8% lower in dispersing individuals than in residents. This might reflect a mortality cost due to dispersal. [ABSTRACT FROM AUTHOR]

Artificial light at night (ALAN) is recognized as one of the major anthropogenic pollutants jeopardizing biodiversity at a global scale. Few studies have focused on the impacts of nocturnal light on freshwater ecosystems despite their increasing exposure to light pollution worldwide due to human activities along rivers or lakes. By modifying metabolism, the disruption of natural light regime could modify the leaf palatability and affect the plant-herbivore interactions which can partly determine the structure of macrophyte communities. By experimentally mimicking light conditions from sub-urban areas, we measured the effects of low-level light at night on the leaf traits of an aquatic plant, Ceratophyllum demersum , and herbivory by the snail Lymnaea stagnalis , a generalist feeder. We demonstrate that artificial light at night increases the herbivory rate: leaves of C. demersum that had been exposed to ALAN for three months were 1.6 times more consumed by L. stagnalis than control leaves. The increase in C. demersum palatability to the pond snail when plants were exposed to ALAN was not due to a decrease in dry matter content or to a modification of the biomechanical characteristics of the leaves. Because snails have not been exposed to nocturnal light before or during the herbivory experiment, this increase in leaf palatability, is possibly linked to modifications of primary and/or secondary metabolism. Our results suggest that ALAN is a potential key factor affecting ecological processes in aquatic ecosystems such as trophic networks. • Freshwater ecosystems are often affected by artificial light at night at low level. • Light pollution changed the palatability to snails of Ceratophyllum demersum leaves. • Lymnaea stagnalis consumed 1.5–2 times more leaves grown under light pollution. • Light pollution did not modify the biomechanical traits of leaves. [ABSTRACT FROM AUTHOR]

Research on contact zones has paid relatively little attention to host–parasite interactions, although these situations have important but different implications depending on whether one considers the host or the parasite's perspective. We investigated both the role of a host contact zone in parasite expansion and whether parasites could influence contact zone dynamics. We studied the diversity and the patterns of parasite exchange (genera Haemoproteus and Plasmodium) infecting two parapatric sibling passerines meeting at a moving contact zone in western Europe. We amplified and sequenced a fragment of the parasite cytochrome b gene. The expanding host harboured more diverse parasites, which might indicate a superior ability to face a diverse parasite fauna than the receding host. Prevalence was very high in both hosts, due to the frequent occurrence of two sister Haemoproteus lineages. Despite the recent movement of the contact zone, these two parasites fitted almost perfectly to the geographic range of their main host species. Yet, we found several cases of cross-species infection in sympatric areas and evidences of asymmetrical spreading of parasites from the expanding host towards the receding host. Altogether, our results suggest that the host contact zone mainly acts as a barrier to parasite expansion even if recurrent host shifts are observed. Besides, they also support the idea that parasite-mediated competition might contribute to the displacement of hosts’ contact zones, thereby emphasizing the role of parasitism on the population dynamics of sympatric species. [ABSTRACT FROM AUTHOR]