References of "Denoël, Mathieu"
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See detailFish introductions, newt decline and paedomorph extinction
Denoël, Mathieu ULg

Scientific conference (2017, May 16)

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See detailMontenegrin ponds and lakes under threat: multiple stressors caused large-scale amphibian decline
Denoël, Mathieu ULg; Kalezić, Miloš; Džukić, Georg et al

Conference (2017, May 03)

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See detailOut of the ground: two coexisting fossorial toad species differ in their emergence and movement patterns
Székely, Diana ULg; Cogalniceanu, Dan; Székely, Paul et al

in Zoology (2017), 121

Understanding the way species with similar niches can coexist is a challenge in ecology.The niche partitioning hypothesis has received much support, positing that species can exploit available resources ... [more ▼]

Understanding the way species with similar niches can coexist is a challenge in ecology.The niche partitioning hypothesis has received much support, positing that species can exploit available resources in different ways. In the case of secretive species, behavioural mechanisms of partitioning are still poorly understood. This is especially true for fossorial frogs because individuals hide underground by day and are active only during the night. We investigated the nocturnal activity and tested the niche partitioning hypothesis in two syntopic fossorial spadefoot toads (Pelobates fuscus and P. syriacus) by examining interspecific variation in emergence from the soil. We employed a night vision recording system combined with video-tracking analyses in a replicated laboratory setting to quantify individual movement patterns, a procedure that has not been used until now to observe terrestrial amphibians. Most individuals appeared on the surface every night and returned to their original burrow (about 60% of the times), or dug a new one around morning. There was a large temporal overlap between the two species. However, P. syriacus was significantly more active than P. fuscus in terms of total distance covered and time spent moving, while P. fuscus individuals left their underground burrow more frequently than P. syriacus. Consequently, P. fuscus adopted more of a sit-and-wait behaviour compared to P. syriacus, and this could facilitate their coexistence. The use of night video-tracking technologies offered the advantage of individually tracking these secretive organisms during their nocturnal activity period and getting fine-grain data to understand their movement patterns. [less ▲]

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See detailThe ‘male escape hypothesis’: sex-biased metamorphosis in response to climatic drivers in a facultatively paedomorphic amphibian
Mathiron, Anthony; Lena, Jean-Paul; Baouch, Sarah et al

in Proceedings of the Royal Society B : Biological Sciences (2017), 284(1853), 20170176

Paedomorphosis is a major evolutionary process that bypasses metamorphosis and allows reproduction in larvae. In newts and salamanders, it can be facultative with paedomorphs retaining gills and ... [more ▼]

Paedomorphosis is a major evolutionary process that bypasses metamorphosis and allows reproduction in larvae. In newts and salamanders, it can be facultative with paedomorphs retaining gills and metamorphs dispersing. The evolution of these developmental processes is thought to have been driven by the costs and benefits of inhabiting aquatic versus terrestrial habitats. In this context, we aimed at testing the hypothesis that climatic drivers affect phenotypic transition and the difference across sexes because sex-ratio is biased in natural populations. Through a replicated laboratory experiment, we showed that paedomorphic palmate newts (Lissotriton helveticus) metamorphosed at a higher frequency when water availability decreased and metamorphosed earlier when temperature increased in these conditions. All responses were sex-biased, and males were more prone to change phenotype than females. Our work shows how climatic variables can affect facultative paedomorphosis and support theoretical models predicting life on land instead of in water. Moreover, because males metamorphose and leave water more often and earlier than females, these results, for the first time, give an experimental explanation for the rarity of male paedomorphosis (the ‘male escape hypothesis’) and suggest the importance of sex in the evolution of paedomorphosis versus metamorphosis. [less ▲]

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See detailOn the identification of paedomorphic and overwintering larval newts based on cloacal shape: review and guidelines
Denoël, Mathieu ULg

in Current Zoology (2017), 63(2), 165-173

Paedomorphosis is an alternative process to metamorphosis in which adults retain larval traits at the adult stage. It is frequent in newts and salamanders, where larvae reach sexual maturity without ... [more ▼]

Paedomorphosis is an alternative process to metamorphosis in which adults retain larval traits at the adult stage. It is frequent in newts and salamanders, where larvae reach sexual maturity without losing their gills. However, in some populations, larvae overwinter in water, while remaining immature. These alternative ontogenetic processes are of particular interest in various research fields, but have different causes and consequences, as only paedomorphosis allows metamorphosis to be bypassed before maturity. It is thus relevant to efficiently identify paedomorphs versus overwintering larvae. In this context, the aim of this paper was threefold: firstly, to perform a meta-analysis of the identification procedures carried out in the literature; secondly, to determine the effectiveness of body size to make inferences about adulthood by surveying natural newt populations of Lissotriton helveticus and Ichthyosaura alpestris, and thirdly, to propose easy guidelines for an accurate distinction between large larvae and paedomorphs based on an external sexual trait, which is essential for reproduction — the cloaca. More than half of the studies in the literature do not mention the diagnostic criteria used for determining adulthood. The criteria mentioned were the presence of mature gonads (10%), eggs laid (4%), courtship behaviour (10%), and external morphological sexual traits (39%) including the cloaca (24%). Body-size thresholds should not be used as a proxy for paedomorphosis, because overwintering larvae can reach a larger size than paedomorphs within the same populations. In contrast, diagnosis based on cloacal external morphology is recommended, as it can be processed by the rapid visual assessment of all caught specimens, thus providing straightforward data at the individual level for both sexes. [less ▲]

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See detailHabitat selection and reproduction of newts in networks of fish and fishless aquatic patches
Winandy, Laurane ULg; Legrand, Pauline ULg; Denoël, Mathieu ULg

in Animal Behaviour (2017), 123

The spatial distribution of organisms in patchy environments can be determined by the relationship between habitat quality and animal behaviour. In species with complex life cycles, such as pond-breeding ... [more ▼]

The spatial distribution of organisms in patchy environments can be determined by the relationship between habitat quality and animal behaviour. In species with complex life cycles, such as pond-breeding amphibians, the selection of a suitable wetland is crucial. While the traditional view of amphibian ecology suggests strong site fidelity and low vagility, more recent research highlights mechanisms involving active site choice through avoidance behaviour and bet-hedging strategies in heterogeneous environments. The introduction of fish to the aquatic environment is one of the factors that may alter site selection and lead to local dispersal. In this context, we investigated the habitat choice of Alpine newts, Ichthyosaura alpestris, in networks of fish (Carassius auratus) and fishless aquatic patches. Using a laboratory design consisting of aquaria divided into two water tanks connected by a terrestrial platform, we assessed newt distribution and movement between patches. During the breeding period, we compared the reproductive success of individuals in two types of networks. We found that newts escaped fish by rapidly changing aquatic patches and then aggregating in safe aquatic patches that were free of fish. In the fish network, newts maintained reproduction, but the high local abundance resulted in decreased sexual activity and egg production and increased use of the terrestrial habitat. However, in the fishless network, newts moved between aquatic patches several times, exhibited more courtship behaviour and laid more eggs than they did in the fish networks. Our results showed both adaptive habitat switching due to environmental risks in the fish network and habitat supplementation (i.e. use of alternative resources) in the fishless network. Such studies on movement behaviour and habitat selection have conservation implications in showing that the persistence of native species in invaded networks depends on the rescue effect, with immigration to fish-free habitats potentially preventing local extinction. [less ▲]

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See detailPond drying cues and their effects on growth and metamorphosis in a fast developing amphibian
Székely, Diana ULg; Denoël, Mathieu ULg; Székely, Paul et al

in Journal of Zoology (2017)

The hydroperiod of breeding habitats imposes a strong selection on amphibians and pond-breeding species usually exhibit a high degree of plasticity in the duration of larval period. However, the potential ... [more ▼]

The hydroperiod of breeding habitats imposes a strong selection on amphibians and pond-breeding species usually exhibit a high degree of plasticity in the duration of larval period. However, the potential for phenotypic plasticity in fast developing species was investigated only in a small number of anurans, and the specific response to environmental cues such as low water versus decreasing water level, as well as the effects of such cues on particular developmental stages, are even less understood. In this context, we investigated the plastic response to pond desiccation in a neotropical species (Ceratophrys stolzmanni) by raising tadpoles in three water level treatments: constant high, constant low and decreasing. The growth rates were the highest reported for amphibian tadpoles (up to 0.3g/day) and the time to metamorphosis was short in all treatments, with the fastest developing tadpole metamorphosing in only 16 days after egg deposition. Individuals from the constant high water level treatment had a higher growth rate than those in the other two treatments, whereas decreasing and constant low water levels had similar effects on development, speeding up metamorphosis. In turn, this involved a cost as these tadpoles had a lower body size and mass at metamorphosis than the ones raised in constant high water levels. The final stages of metamorphosis, when tadpoles are the most vulnerable, were shorter in tadpoles exposed to a decreasing water level, allowing them to leave water quickly. Our experiment demonstrates that phenotypic plasticity is maintained even in environments devoid of permanent aquatic habitats. Ceratophryd tadpoles are able to shorten their developmental time when they perceive a risk of desiccation and react similarly to cues coming from the two unfavorable water conditions showing their adaptation to ephemeral and unpredictable breeding habitats. [less ▲]

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See detailFeeding ecology of metamorphic and paedomorphic palmate newts (Lissotriton helveticus) in Larzac
Didaskalou, Emilie; Lejeune, Benjamin ULg; Lepoint, Gilles ULg et al

Poster (2016, December 16)

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See detailPoissons, tritons et pédomorphes
Denoël, Mathieu ULg

Scientific conference (2016, November 25)

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See detailPhenotypic plasticity in a fossorial toad from a Pacific xeric forest (Ecuador)
Székely, Diana ULg; Szekely, Paul; Denoël, Mathieu ULg et al

Poster (2016, October 06)

For amphibians, optimal size at metamorphosis is determined by a trade-off between opportunities for growth and risks of mortality in aquatic and terrestrial habitats, and many species show a high degree ... [more ▼]

For amphibians, optimal size at metamorphosis is determined by a trade-off between opportunities for growth and risks of mortality in aquatic and terrestrial habitats, and many species show a high degree of plasticity in time and size at metamorphosis that allow them to adapt to unpredictable environments. We used as model a neotropical anuran species, the Pacific horned frog, Ceratophrys stolzmanni, that inhabits the Tumbesian dry forests of southwestern Ecuador, and lays its eggs in lentic habitats of variable size and unpredictable duration. We investigated (i) how tadpoles time their metamorphosis in order to escape a rapidly drying aquatic habitat, and (ii) the consequences of metamorphosis plasticity on the immediate and mid-term fitness of individuals. We conducted two experiments; in the first one we exposed 36 tadpoles to one of three water levels treatments: constant high, decreasing and constant low. Tadpoles that were raised in decreasing or low water level metamorphosed on average 13% and 10% faster than the ones from constant high water level, but at a lower body size and mass. Growth rates were among the highest recorded for tadpoles and individuals from the constant high water level treatment grew at a much faster rate than the others. In a second experiment, we sampled 72 freshly metamorphosed (Gosner stage 45) C. stolzmanni individuals of assorted sizes (SVL between 23.8 and 47.9 mm, body weight between 1.2 and 11.9 g). From this spectrum of sizes, we selected the 21 largest and 22 smallest individuals and evaluated the effects of body size at metamorphosis on trophic and locomotory performance parameters. We determined their growth rate and survival over the course of an activity season (i.e., two months). Our results show that bigger size at metamorphosis is correlated with better survival chances and performance. Larger individuals were more mobile, had bigger gape width and better survival rates (95% compared to 64% for small individuals). Growth rates were not correlated with initial size, and small individuals were capable of increasing their size at a higher rate. This indicates that, although size at metamorphosis has an immediate impact on fitness, smaller individuals are able to compensate with an increased growth rate. [less ▲]

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See detailWho are the winners in the race against desiccation – phenotypic plasticity in a fossorial toad
Székely, Diana ULg; Székely, Paul; Denoël, Mathieu ULg et al

Conference (2016, September 29)

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See detailUn morso di più: ecologia del cannibalismo in Salamandra salamandra
Melotto, Andrea; Manenti, Raoul; Ficetola, Francesco et al

Conference (2016, September 23)

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See detailRole of phenotypic plasticity and local adaptation in allowing cave exploitation: ecological and evolutionary insights from the fire salamander
Manenti, Raoul; Melotto, Andrea; Tagliaferro, L. et al

Conference (2016, August 31)

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See detailAmphibians breeding in refuge habitats have larvae with stronger antipredator responses
Manenti, Raoul; Melotto, Andrea; Denoël, Mathieu ULg et al

in Animal Behaviour (2016), 118

Antipredator responses are a key determinant of the successful persistence of prey, and behavioural modifications are a frequent antipredator strategy. However, conspecific populations often inhabit ... [more ▼]

Antipredator responses are a key determinant of the successful persistence of prey, and behavioural modifications are a frequent antipredator strategy. However, conspecific populations often inhabit heterogeneous environments. This can determine local adaptations, and might also induce variation in antipredator responses. Nevertheless, there is limited information on whether heterogeneity of predation risk among populations determines variation in antipredator response. Here we studied the fire salamander, Salamandra salamandra, a species that can breed in both surface streams and caves, habitats that are predator-rich and predator-free, respectively, and measured differences in antipredator responses across populations with different predation risk. We combined field surveys and laboratory experiments to understand the role of predation risk on the activity patterns of larvae, while measuring behavioural differences between populations. We reared larvae from different habitats in safe and risky conditions and tested their response to predator cues before and after rearing. In the field, predation risk was much higher in surface streams than in caves; larvae moved more in the absence of predators and when the light intensity was low. During laboratory experiments, larvae were less active if reared in risky conditions, but cave larvae showed a stronger response to risk than stream larvae. Therefore, larvae from sites without predators showed higher antipredator responses than those from risky habitats. This response fits the predictions of the risk allocation model, in which prey from habitats with a high background level of risk need to be active even when predators are present, to satisfy their energetic demands. Our findings show that antipredator behaviour may differ strongly between populations and stress the importance of integrating this variability in studies on predatory responses. [less ▲]

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See detailHigh gene flow between alternative morphs and the evolutionary persistence of facultative paedomorphosis
Oromi Farrús, Neus ULg; Michaux, Johan ULg; Denoël, Mathieu ULg

in Scientific Reports (2016), 6

Paedomorphosis and metamorphosis are two major developmental processes that characterize the evolution of complex life cycles in many lineages. Whereas these processes were fixed in some taxa, they ... [more ▼]

Paedomorphosis and metamorphosis are two major developmental processes that characterize the evolution of complex life cycles in many lineages. Whereas these processes were fixed in some taxa, they remained facultative in others, with alternative phenotypes expressed in the same populations. From a genetic perspective, it is still unknown whether such phenotypes form a single population or whether they show some patterns of isolation in syntopy. This has deep implications for understanding the evolution of the phenotypes, i.e. towards their persistence or their fixation and speciation. Newts and salamanders are excellent models to test this hypothesis because they exhibit both developmental processes in their populations: the aquatic paedomorphs retain gills, whereas the metamorphs are able to colonize land. Using microsatellite data of coexisting paedomorphic and metamorphic palmate newts (Lissotriton helveticus), we found that they formed a panmictic population, which evidences sexual compatibility between the two phenotypes. The high gene flow could be understood as an adaptation to unstable habitats in which phenotypic plasticity is favored over the fixation of developmental alternatives. This makes then possible the persistence of a polyphenism: only metamorphosis could be maintained in case of occasional drying whereas paedomorphosis could offer specific advantages in organisms remaining in water. [less ▲]

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See detailTemporal habitat shift of a polymorphic newt species under predation risk
Winandy, Laurane ULg; Colin, Mélanie; Denoël, Mathieu ULg

in Behavioral Ecology (2016), 27(4), 1025-1032

The temporal partitioning hypothesis suggests that the evolution of different diel activity rhythms in animals might facilitate the coexistence between prey and predators. However, the temporal shift of ... [more ▼]

The temporal partitioning hypothesis suggests that the evolution of different diel activity rhythms in animals might facilitate the coexistence between prey and predators. However, the temporal shift of habitat use induced by predation has rarely been observed. The study of such a mechanism is particularly relevant for introduced species because it might explain how native species can persist or decline in response to the presence of alien species. The introduction of fish into ponds inhabited by amphibians has severe consequences for their occurrence and abundance. Fish particularly affect an alternative newt phenotype, the paedomorph, which does not undergo metamorphosis and maintains larval traits such as gills at the adult stage. In a laboratory design, we assessed the diel patterns of habitat use in the 2 distinct morphological phenotypes of palmate newt (Lissotriton helveticus) in the presence or absence of goldfish (Carassius auratus). Both newt phenotypes avoided a risky habitat more in the presence than in the absence of fish. This habitat shift was more pronounced during the daytime (i.e., when the risk could be considered higher for the newts) than during nighttime. However, in contrast to metamorphs, paedomorphs showed less adaptive changes according to temporal risk and remained in their shelter for most of the time. Temporal and habitat partitioning at the diel scale between native and alien species might promote their coexistence, but diel change can also imply a cost in the overall reduction of the time allocated to essential activities, showing that species interactions remain complex. [less ▲]

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