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See detailThe importance of phenotypic diversity in conservation: Resilience of palmate newt morphotypes after fish removal in Larzac ponds (France)
Denoël, Mathieu ULg; Winandy, Laurane ULg

in Biological Conservation (2015), 192

Resilience of organisms after threat removal is an essential feature to justify conservation efforts. Amphibians are particularly threatened with a worldwide decline, showing a low resistance to invaders ... [more ▼]

Resilience of organisms after threat removal is an essential feature to justify conservation efforts. Amphibians are particularly threatened with a worldwide decline, showing a low resistance to invaders such as fish. Previous research has shown that they could recover after fish extirpation due to metamorphosed colonizers. However, not all amphibian phenotypes are able to persist to fish introduction and disperse. In many species of newts and salamanders, paedomorphs retain gills in the adult stage, which makes them fully aquatic. A proposed way to conserve this phenotype would be to remove introduced fish from their habitats. However, because paedomorphosis is usually not expressed in the presence of fish, it is unknown whether fish removal could allow the resilience of paedomorphs. This would be possible only if progenies of metamorphosed individuals could become paedomorphic in restored habitats. Through a quantitative survey in three types of ponds, including control ponds without fish, ponds in which fish were extirpated, and fish ponds, we determined abundances of paedomorphic and metamorphic palmate newts (Lissotriton helveticus). The results show that paedomorphosis resilience is possible and even highly frequent, as paedomorphs were found in 80% of ponds where fish disappeared. Abundances were similar between these ponds and control ponds whereas fish ponds had almost no newts, indicating a very low resistance to invaders. This shows that conserving common phenotypes can help to preserve endangered phenotypes, as paedomorphs were produced through the reproduction of metamorphs. There is thus hope of maintaining intraspecific biodiversity though conservation action involving threat removal. [less ▲]

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See detailThe aggressive personality of an introduced fish affects foraging behavior in a polymorphic newt
Winandy, Laurane ULg; Denoël, Mathieu ULg

in Behavioral Ecology (2015), 26(6), 1528-1536

The study of personality has aroused much interest and has provided insight into the understanding of animal behavior. Nevertheless, the study of the ecological consequences of personality is a newer ... [more ▼]

The study of personality has aroused much interest and has provided insight into the understanding of animal behavior. Nevertheless, the study of the ecological consequences of personality is a newer field that could shed light on cases of alien species introductions. The goldfish (Carassius auratus) is frequently introduced worldwide and affects the abundance of newts, having an especially negative impact on an alternative phenotype, the paedomorph, which maintains larval traits at the adult stage, unlike the other phenotype, the metamorph, which has undergone metamorphosis. We experimentally assessed the impact of goldfish on the foraging behavior of both phenotypes of palmate newts (Lissotriton helveticus). More particularly, we assessed fish personality by analyzing the foraging activity and the aggressiveness toward newts, and newt personality by analyzing individual difference in boldness. In the presence of fish, fewer newts foraged than in their absence, and paedomorphs were more affected than metamorphs. We found strong personality differences in fish and fewer newts foraged in the presence of a more aggressive fish. Newts differed in boldness, but fish aggressiveness remains a key factor to explain newt behavior. Studying behavioral interactions between native and alien species helps to understand the mechanisms of coexistence and exclusion and why different phenotypes might be affected differently by the same threat. To a great extent, not only the presence of fish alters the foraging opportunities of newts but also the personality of the invader; integrating personality patterns of invaders is therefore a key to understanding the ecological consequences of alien species introduction. [less ▲]

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See detailAmphibians forgo aquatic life in response to alien fish introduction
Winandy, Laurane ULg; Darnet, Elodie; Denoël, Mathieu ULg

in Animal Behaviour (2015), 109

Species with complex life cycles are good models to understand trade-offs between life in hostile and favourable habitats. Newts remain in breeding wetlands for a long period and are strongly affected by ... [more ▼]

Species with complex life cycles are good models to understand trade-offs between life in hostile and favourable habitats. Newts remain in breeding wetlands for a long period and are strongly affected by fish introduction; however, mechanisms of the exclusion observed in the field are still not well known. In particular, whether newts skip breeding and leave water for land in response to fish introduction and how aquatic shelter may influence their choice remain open questions. To investigate these questions, we experimentally studied the use of aquatic and terrestrial habitats during the breeding season of palmate newts, Lissotriton helveticus, in the presence and absence of goldfish, Carassius auratus. We determined the consequences of habitat choice on newt fitness by assessing sexual activity and number of eggs. There was a strong, significant avoidance of the aquatic environment in the presence of fish, particularly when no aquatic shelter was available. This escape from the water had an impact on reproduction: newts decreased their sexual activity and laid fewer eggs. The availability of shelters favoured coexistence but did not prevent a large proportion of the newts from leaving water and skipping reproduction. This study shows how the presence of fish and the absence of aquatic shelters can lead to newts forgoing aquatic life, thus improving our understanding of the mechanisms behind the coexistence and exclusion patterns found in the wild. More broadly, these data contribute to explaining aquatic versus terrestrial life in favourable and unfavourable environments. [less ▲]

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

in Ecological Applications (2015), 25(7), 1922-1931

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 detailPredator cues and risky habitats affect foraging activity in salamanders
Melotto, Andrea; Ficetola, Gentile Francesco; Denoël, Mathieu ULg et al

Conference (2015, September 11)

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See detailNewts skip aquatic life and forego reproduction in response to alien fish introduction
Winandy, Laurane ULg; Darnet, Elodie; Denoël, Mathieu ULg

Conference (2015, September 10)

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See detailReevaluating IUCN Red List assesment on European amphibians
Crnobrnja-Isailović, Jelka; Cogalniceanu, Dan; Denoël, Mathieu ULg et al

Conference (2015, September 09)

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See detailBehavioral effects of exposure to salinity on tadpoles of two syntopic species of spadefoot toads (genus Pelobates)
Székely, Diana ULg; Stanescu, Floriana; Székely, Paul et al

Poster (2015, September)

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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 (2015), 28(5), 1049-1056

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 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 triclosan on behaviour and neural development of Cyprinodon variegatus
Benichou, Farida; Rahmouni, Chahrazed; Denoël, Mathieu ULg et al

Poster (2014, December 12)

The study focussed on the effects of triclosan (TCS) exposure on mobility and hearing capacities of Cyprinodon variegatus larvae. TCS is an omnipresent antimicrobial and contaminant of aquatic ecosystems ... [more ▼]

The study focussed on the effects of triclosan (TCS) exposure on mobility and hearing capacities of Cyprinodon variegatus larvae. TCS is an omnipresent antimicrobial and contaminant of aquatic ecosystems, which can act as endocrine disruptor, mainly by modifying thyroid functioning. Larval stages are particularly vulnerable to deleterious effects of endocrine disrupters because of potential impairment of fish development and behaviour. Exposure to TCS was conducted at fertilization of eggs at concentrations likely to be found in the environment: 20, 50 and 100 μg.l-1. The analysis of growth parameters of C. variegatus showed no effect of TCS on the fertility of eggs, survival and larval weight. Subsequently, THs concentrations were measured on 15 days post hatching larvae. THs are initially produced as T4 (thyroxine) cells and then converted in the bioactive form of T3 (triiodothyronine) cells. The observed increase of T4 and T3 cells in larvae exposed to 50 and 100 μg.l-1 suggests an increase in THs synthesis as a consequence of TCS exposure. Auditory thresholds of larvae were determined using ABR (Auditory Brainstem Response) technique, and finally larval mobility was measured. For both parameters no significant differences were observed among the three different treatments. Audiograms showed that the auditory system is not yet completely established at 30 days post hatching. However, these results allowed us to consider C. variegatus as an “hearing generalist” because this species have a hearing sensitivity lower than 2000 Hz. Regarding locomotion, our result summarized short time experiences targeting only swimming speed, distance and degree of mobility. It would be interesting to expand the behavioural aspects on other parameters of locomotion and integrate Cyprinodon reaction to different stress (light or touch). In conclusion, our results require an extensive long-term study on the full life cycle of C. variegatus, in order to evaluate the impact of triclosan on neural function and behaviour through several generations. [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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