References of "Denoël, Mathieu"
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See detailNewt life after fish introduction: extirpation of paedomorphosis in a mountain fish lake and newt use of satellite pools
Denoël, Mathieu ULg; Scime, Patrick; Zambelli, Nicola

in Current Zoology (in press), 62

Fish introduction is one of the main causes of amphibian decline worldwide. It affects particularly rare aquatic phenotypes such as paedomorphs, which retain gills during the adult stage. In this context ... [more ▼]

Fish introduction is one of the main causes of amphibian decline worldwide. It affects particularly rare aquatic phenotypes such as paedomorphs, which retain gills during the adult stage. In this context, we determined whether small wetlands, such as pools surrounding fished and fishless lakes, could sustain paedomorphic and metamorphic newts. To this end, we surveyed lakes known historically to sustain Alpine newts (Ichthyosaura alpestris) as well as 35 nearby pools. On the basis of the published records, the only known population exhibiting paedomorphosis in the Swiss Alps was found to be extirpated by salmonid introductions. However, the metamorphs persisted in peripheral pools, paedomorphosis was discovered at a new locality, and overwintering larvae were still present in one of the lakes. These results show the importance of conserving varied aquatic habitats such as pools in mountainous environments where the main resources can become unsuitable for amphibians because of fish introductions. Pools may also function as reservoirs in maintaining newt populations until programs to remove fish from lakes can be carried out. It is not known if paedomorphs could reappear after fish removal. However, the combined resilience of amphibians after fish removal and the genetic basis for paedomorphosis highlighted in other taxa by previous studies suggest that there is the potential to maintain this intraspecific case of diversity even after its disappearance. [less ▲]

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See detailExpression of sexual ornaments in a polymorphic species: phenotypic variation in response to environmental risk
Winandy, Laurane ULg; Denoël, Mathieu ULg

in Journal of Evolutionary Biology (in press)

Secondary sexual traits may evolve under the antagonistic context of sexual and natural selection. In some polymorphic species, these traits are only expressed during the breeding period and are ... [more ▼]

Secondary sexual traits may evolve under the antagonistic context of sexual and natural selection. In some polymorphic species, these traits are only expressed during the breeding period and are differently expressed in alternative phenotypes. However, it is unknown whether such phenotypes exhibit phenotypic plasticity of seasonal ornamentations in response to environmental pressures such as in the presence of fish (predation risk). This is an important question to understand the evolution of polyphenisms. We used facultative paedomorphosis in newts as a model system because it involves the coexistence of paedomorphs that retain gills in the adult stage with metamorphs that have undergone metamorphosis, but also because newts exhibit seasonal sexual traits. Our aim was therefore to determine the influence of fish on the development of seasonal ornamentation in the two phenotypes of the palmate newt (Lissotriton helveticus). During the entire newt breeding period, we assessed the importance of phenotype and fish presence with an information-theoretic approach. Our results showed that paedomorphs presented much less developed ornamentation than metamorphs and those ornamentations varied over time. Fish inhibited the development of sexual traits but differently between phenotypes: in contrast to metamorphs, paedomorphs lack the phenotypic plasticity of sexual traits to environmental risk. This study points out that internal and external parameters act in complex ways in the expression of seasonal sexual ornamentations and that similar environmental pressure can induce a contrasted evolution in alternative phenotypes. [less ▲]

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See detailUsing kernels and ecological niche modelling to delineate conservation areas in an endangered patch-breeding phenotype
Denoël, Mathieu ULg; Ficetola, Francesco

in Ecological Applications (in press)

Efficient delineation of conservation areas is a great challenge in maintaining biodiversity. Kernel density estimators (KDEs) are a powerful tool in this perspective, but they have not been applied at ... [more ▼]

Efficient delineation of conservation areas is a great challenge in maintaining biodiversity. Kernel density estimators (KDEs) are a powerful tool in this perspective, but they have not been applied at the population level on patch-distributed organisms. This would be particularly worthy for species that need broad habitats beyond those where they can be sampled; such as terrestrial lands for pond-breeding amphibians. The aim of this study was to compare different approaches for the identification of suitable areas for conservation: KDE, ecological niche modelling, and a combination of KDE and niche models. Paedomorphosis was chosen as a model system because this is an important form of intraspecific variation that is present in numerous taxa, but geographically localized within species and globally endangered. 277 ponds were sampled in one of the hotspots of paedomorphosis to determine the abundance and distribution of paedomorphs (i.e. individuals retaining gills at the adult stage) of the palmate newt (Lissotriton helveticus), with emphasis on the connections between the most valuable populations. KDEs gave insights into the surface areas required to balance the maintenance of certain number of connected ponds and the respective number of disjoint areas in which the whole population is divided. The inclusion of barriers in the models helped in accurately designing the limits of the areas to protect. Alone, habitat models were not able to successfully delineate the area to protect, but the integration between terrestrial suitable areas or barriers and KDE allowed an objective identification of areas required for conservation. Overall, the best performance was observed by the KDE integrating ecological barriers, and by the combination between KDE and niche modelling. In a broader perspective, KDEs are thus a pertinent tool in providing quantitative spatial measurements to delineate conservation areas based on patch-abundance data with a specific focus to connectivity. [less ▲]

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See detailEffects of low dose endosulfan exposure on brain neurotransmitter levels in the African clawed frog Xenopus laevis
Preud'Homme, Valérie; Milla, Sylvain; Gillardin, Virginie et al

in Chemosphere (2015), 120(2), 357-364

Understanding the impact of pesticides in amphibians is of growing concern to assess the causes of their decline. Among pesticides, endosulfan belongs to one of the potential sources of danger because of ... [more ▼]

Understanding the impact of pesticides in amphibians is of growing concern to assess the causes of their decline. Among pesticides, endosulfan belongs to one of the potential sources of danger because of its wide use and known effects, particularly neurotoxic, on a variety of organisms. However, the effect of endosulfan was not yet evaluated on amphibians at levels encompassing simultaneously brain neurotransmitters and behavioural endpoints. In this context, tadpoles of the African clawed frog Xenopus laevis were submitted to four treatments during 27 d: one control, one ethanol control, and two low environmental concentrations of endosulfan (0.1 and 1 μg L−1). Endosulfan induced a significant increase of brain serotonin level at both concentrations and a significant increase of brain dopamine and GABA levels at the lower exposure but acetylcholinesterase activity was not modified by the treatment. The gene coding for the GABA transporter 1 was up-regulated in endosulfan contaminated tadpoles while the expression of other genes coding for the neurotransmitter receptors or for the enzymes involved in their metabolic pathways was not significantly modified by endosulfan exposure. Endosulfan also affected foraging, and locomotion in links with the results of the physiological assays, but no effects were seen on growth. These results show that low environmental concentrations of endosulfan can induce adverse responses in X. laevis tadpoles. At a broader perspective, this suggests that more research using and linking multiple markers should be used to understand the complex mode of action of pollutants. [less ▲]

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See detailImpact of goldfish on terrestrial and aquatic microhabitat use in the palmate newt
Darnet, Elodie; Winandy, Laurane ULg; Denoël, Mathieu ULg

Poster (2014, December 12)

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See detailRensch’s rule and sexual dimorphism in salamanders: patterns and potential processes
Colleoni, E.; Denoël, Mathieu ULg; Padoa-Schioppa, E. et al

in Journal of Zoology (2014), 293(3), 143-151

Body size is influenced by the interaction of multiple forces, whose effects can determine the occurrence of sexual size dimorphism (SSD). Rensch's rule is the increase of SSD with body size in taxa where ... [more ▼]

Body size is influenced by the interaction of multiple forces, whose effects can determine the occurrence of sexual size dimorphism (SSD). Rensch's rule is the increase of SSD with body size in taxa where males are the largest sex, and the opposite pattern in female-biased SSD taxa. This pattern was detected in many animal groups, but contrasting results were also highlighted. This study evaluated the existence of Rensch's patterns for body size and for the number of caudal vertebrae in salamandrid caudate amphibians. Furthermore, we tested the support of alternative hypotheses on processes that may determine allometric patterns: sexual selection, fecundity selection and constraining selection by performing separate analyses on species with male- and female-biased SSD. We used the literature and original data to gather information on body size and number of caudal vertebrae in 52 species of salamandrids over four continents. We then tested the support of the three hypotheses using a phylogenetic approach. Rensch's rule was valid for body size in salamanders only for species with male-biased dimorphism. No allometric relationships were detected by analyses on all the species, or by analyses on female-biased SSD species. Analyses performed on the number of caudal vertebrae showed no significant patterns. Our study supports the role of sexual selection in promoting positive allometry for body size in male-biased SSD species, whereas the alternative hypotheses were not supported by our data. These results highlight the importance of distinguishing male- and female-biased species as different evolutionary pressures and constraints may be at the basis of evolution of SSD in these groups. [less ▲]

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See detailFire salamander (Salamandra salamandra) in Larzac plateau: low occurrence, pond-breeding and cohabitation of larvae with paedomorphic palmate newts (Lissotriton helveticus)
Denoël, Mathieu ULg; Winandy, Laurane ULg

in Acta herpetologica (2014), 9(1), 43-49

Alternative reproductive strategies are widespread in caudate amphibians. Among them, fire salamanders (Salamandra salamandra) usually rely on streams to give birth to aquatic larvae but also use ponds ... [more ▼]

Alternative reproductive strategies are widespread in caudate amphibians. Among them, fire salamanders (Salamandra salamandra) usually rely on streams to give birth to aquatic larvae but also use ponds, whereas palmate newt larvae (Lissotriton helveticus) typically metamorphose into terrestrial juveniles, but can also reproduce in retaining their gills, a process known as paedomorphosis. Here we report repeated observations of an unusual case of coexistence of these two alternative traits in the same pond (Larzac, France). The prevalence of fire salamanders in Southern Larzac was very low (pond occupancy: 0.36%). The observed abundance of fire salamander larvae and paedomorphic newts was also low in the studied pond. On one hand, the rarity of this coexistence pattern may suggest that habitat characteristics may not be optimal or that competition or predation processes might be operating. However, these hypotheses remain to be tested. On the other hand, as this is the only known case of breeding in Southern Larzac, it could be considered to be at a high risk of extirpation. [less ▲]

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See detailHeterochrony in a complex world: disentangling environmental processes of facultative paedomorphosis in an amphibian
Denoël, Mathieu ULg; Ficetola, Gentile Francesco

in Journal of Animal Ecology (2014), 83(3), 606-615

1. Heterochrony, the change in the rate or timing of development between ancestors and their descendants, plays a major role in evolution. When heterochrony produces polymorphisms, it offers the ... [more ▼]

1. Heterochrony, the change in the rate or timing of development between ancestors and their descendants, plays a major role in evolution. When heterochrony produces polymorphisms, it offers the possibility to test hypotheses that could explain its success across environments. Amphibians are particularly suitable to exploring these questions because they express complex life cycles (i.e. metamorphosis) that have been disrupted by heterochronic processes (paedomorphosis: retention of larval traits in adults). The large phenotypic variation across populations suggests that more complex processes than expected are operating, but they remain to be investigated through multivariate analyses over a large range of natural populations across time. 2. In this study we compared the likelihood of multiple potential environmental determinants of heterochrony. We gathered data on the proportion of paedomorphic and metamorphic palmate newts (Lissotriton helveticus) across more than 150 populations during 10 years, and used an information-theoretic approach to compare the support of multiple potential processes. 3. Six environmental processes jointly explained the proportion of paedomorphs in populations: predation, water availability, dispersal limitation, aquatic breathing, terrestrial habitat suitability, and anti-predator refuges. Analyses of variation across space and time supported models based on the advantage of paedomorphosis in favourable aquatic habitats. 4. Paedomorphs were favoured in deep ponds, in conditions favourable to aquatic breathing (high oxygen content), with lack of fish, and surrounded by suitable terrestrial habitat. Metamorphs were favoured by banks allowing easy dispersal. 5. These results indicate that heterochrony relies on complex processes involving multiple ecological variables and exemplifies why heterochronic patterns occur in contrasted environments. On the other hand, the fast selection of alternative morphs shows that metamorphosis and paedomorphosis developmental modes could be easily disrupted in natural populations. [less ▲]

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See detailHabitat use of a population of bottlenose dolphins, Tursiops truncatus gephyreus, analyzed by means of Kernel Density Estimation (KDE) method
Cransveld, Alice ULg; Denoël, Mathieu ULg; Das, Krishna ULg et al

Poster (2014, April 09)

The San Antonio Bay (SAB), in Patagonia, Argentina, harbors a resident population of bottlenose dolphins (Tursiops truncatus gephyreus). It seems a privileged area to give birth and nurse calves. In the ... [more ▼]

The San Antonio Bay (SAB), in Patagonia, Argentina, harbors a resident population of bottlenose dolphins (Tursiops truncatus gephyreus). It seems a privileged area to give birth and nurse calves. In the context of declining populations worldwide and more particularly in South America, preserving the SAB population takes a considerable significance. Yet the SAB is facing human population growth and touristic development, which represent potential threats for the dolphin population, especially dolphin-watching activities. In this context, the aim of this study was to understand the bottlenose dolphin’s habitat use within the bay, and to consider how this information could be used in prospective management strategies. Particularly, we aimed at using the Kernel Density Estimation (KDE) method to map the intensity of space use for essential behavioural patterns. To this end, we collected behavioural information on dolphins during 25 boat-based surveys in the bay in 2011. The habitat use of the bay was heterogeneous: some areas were more intensely used than others. Dolphins spent most of their time traveling and diving. Variables associated to resting behaviours, e.g. school size and depth, indicated that the SAB would be a safer place compared to other known residency areas, confirming its suitability for conservation purposes. KDE analyses showed that behaviours are not evenly distributed inside the bay. Bottlenose dolphins being more sensitive to anthropogenic disturbances while engaged in resting or socializing behaviours, it is crucial to locate these behaviours. In SAB, the KDE shows that resting and socializing areas are located in the Northern part of the bay, indicating that it should constitute a priority protected area in potential future management strategies. Furthermore, our results show that the KDE method is an appropriate and advantageous tool when determining critical habitats, worth being more widely used. [less ▲]

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See detailFacultative paedomorphosis and the pattern of intra- and interspecific variation in cranial skeleton: lessons from European newts (Ichthyosaura alpestris and Lissotriton vulgaris)
Ivanović, Ana; Cvijanović, Milena; Denoël, Mathieu ULg et al

in Zoomorphology (2014), 133(1), 99-109

Paedomorphosis, the presence of ancestral larval and juvenile traits that occur at the descendent adult stage, is an evolutionary phenomenon that shaped morphological evolution in many vertebrate lineages ... [more ▼]

Paedomorphosis, the presence of ancestral larval and juvenile traits that occur at the descendent adult stage, is an evolutionary phenomenon that shaped morphological evolution in many vertebrate lineages, including tailed amphibians. Among salamandrid species, paedomorphic and metamorphic phenotypes can be observed within single populations (facultative paedomorphosis). Despite wide interest in facultative paedomorphosis and polymorphism produced by heterochronic changes (heterochronic polymorphism), the studies that investigate intraspecific morphological variation in facultative paedomorphic species are largely missing. By quantifying the cranium size and development (bone development and remodeling), we investigated the variation at multiple levels (i.e., between sexes, populations and species) of two facultatively paedomorphic European newt species: the alpine and the smooth newt. The pattern of variation between paedomorphs (individuals keeping larval traits at the adult stage) and metamorphs (metamorphosed adult individuals) varied between species and among populations within a single species. The patterns of variation in size and skull formation appear to be more uniform in the alpine than in the smooth newt, indicating that developmental constraints differed between species (more pronounced in alpine than in smooth newt). Our study shows that the cranial skeleton provides detailed insight in the pattern of variation and divergence in heterochronic polymorphism within and between species and open new questions related to heterochronic polymorphism and evolution of cranial skeleton. [less ▲]

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See detailUpdated distribution and biogeography of amphibians and reptiles of Europe
Silero, Neftali; Campos, João; Bonardi, Anna et al

in Amphibia-Reptilia (2014), 35(1), 1-31

A precise knowledge of the spatial distribution of taxa is essential for decision-making processes in land management and biodiversity conservation, both for present and under future global change ... [more ▼]

A precise knowledge of the spatial distribution of taxa is essential for decision-making processes in land management and biodiversity conservation, both for present and under future global change scenarios. This is a key base for several scientific disciplines (e.g. macro-ecology, biogeography, evolutionary biology, spatial planning, or environmental impact assessment) that rely on species distribution maps. An atlas summarizing the distribution of European amphibians and reptiles with 50×50 km resolution maps based on ca. 85,000 grid records was published by the Societas Europaea Herpetologica (SEH) in 1997. Since then, more detailed species distribution maps covering large parts of Europe became available, while taxonomic progress has led to a plethora of taxonomic changes including new species descriptions. To account for these progresses, we compiled information from different data sources: published in books and websites, ongoing national atlases, personal data kindly provided to the SEH, the 1997 European Atlas, and the Global Biodiversity Information Facility (GBIF). Databases were homogenised, deleting all information except species names and coordinates, projected to the same coordinate system (WGS84) and transformed into a 50×50 km grid. The newly compiled database comprises more than 384,000 grid and locality records distributed across 40 countries. We calculated species richness maps as well as maps of Corrected Weighted Endemism and species distribution types (i.e. groups of species with similar distribution patterns) by hierarchical cluster analysis using Jaccard’s index as association measure. Our analysis serves as a preliminary step towards an interactive, dynamic and online distributed database system (NA2RE system) of the current spatial distribution of European amphibians and reptiles (see http://na2re.ismai.pt). The NA2RE system will serve as well to monitor potential temporal changes in their distributions. Grid maps of all species are made available along with this paper as a tool for decision-making and conservation-related studies and actions. We also identify taxonomic and geographic gaps of knowledge that need to be filled, and we highlight the need to add temporal and altitudinal data for all records, to allow tracking potential species distribution changes as well as detailed modelling of the impacts of land use and climate change on European amphibians and reptiles. [less ▲]

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See detailIntroduced goldfish affect amphibians through inhibition of sexual behaviour in risky habitats: an experimental approach
Winandy, Laurane ULg; Denoël, Mathieu ULg

in PLoS ONE (2013), 8(11), 82736

The introduction of alien species is one of the major causes of current and global biodiversity loss. The introduction of fish can be a particular threat to native amphibian populations, which are ... [more ▼]

The introduction of alien species is one of the major causes of current and global biodiversity loss. The introduction of fish can be a particular threat to native amphibian populations, which are declining worldwide. One way for amphibians to persist in such altered environments is to adopt anti-predator strategies especially at the behavioural level. However, although it has been shown that avoidance behaviour may decrease the probability of being detected by a potential predator, little is known on the consequences on sexual behaviour. In this study, we tested the hypothesis that adult Alpine newts (Ichthyosaura alpestris) use shelters more often and exhibit less sexual activity in the presence of goldfish (Carassius auratus) and that they reduce sexual activity more in risky micro-habitats than in safe environments. To this end, we assessed behavioural patterns of adult newts in a replicated laboratory design. Goldfish were present in direct contact with newts in half of the tanks. Consistently throughout the study period, significantly more newts used shelter in the presence of fish than in their absence. Newts also significantly decreased their sexual activity level overall, but specially outside the shelter when they were in direct contact with fish. These results show that fish presence can affect newts in complex ways, such as through inhibition of their reproduction. Our work highlights that integrating behaviour in conservation studies is essential to understanding the patterns of coexistence and exclusion between introduced fish and amphibians. [less ▲]

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See detailDifferences in locomotor activity in two syntopic spadefoot toad species (genus Pelobates)
Székely, Diana; Denoël, Mathieu ULg; Székely, Paul et al

Poster (2013, August 25)

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See detailNA2RE Project—The new atlas of amphibians and reptiles: new compilation and online system
Sillero, Neftalí; Campos, João; Oliveira, Marco Amaro et al

Conference (2013, August 24)

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See detailEnvironmental correlates of paedomorphosis and metamorphosis in palmate newts
Denoël, Mathieu ULg; Ficetola, G. Francesco

Conference (2013, August 23)

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See detailDoes foraging plasticity favours adaptation to new habitats in fire salamanders? Preliminary data
Manenti, Raoul; Denoël, Mathieu ULg; Ficetola, Gentile Francesco

Conference (2013, August 23)

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