References of "Denoël, Mathieu"
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See detailEffects of widespread fish introductions on paedomorphic newts in Europe
Denoël, Mathieu ULg; Džukić, Georg; Kalezic, Milos L.

in Conservation Biology (2005), 19(1), 162-170

As a result of factors such as global warming, habitat destruction, and species introduction, amphibians are declining worldwide. No one, however, has analyzed the status of polymorphic amphibian species ... [more ▼]

As a result of factors such as global warming, habitat destruction, and species introduction, amphibians are declining worldwide. No one, however, has analyzed the status of polymorphic amphibian species at a national or continental scale, although some local reports exist. Our aim was to report on the loss of intraspecific heterochrony as a loss to diversity in determining the consequences of fish stocking on European populations of paedomorphic newts. Paedomorphosis is a polymorphism in which larval traits are retained in the adult stage. We surveyed 39 paedomorphic populations of the alpine ( Triturus alpestris) and palmate ( T. helveticus) newts, all but one of which initially occupied fishless ponds and lakes in France, Italy, Slovenia, Bosnia, Montenegro, and Greece. Exotic fishes were found in 44% of the studied aquatic habitats, with a 100% presence in Montenegro. At all sites paedomorphs disappeared and metamorphs declined. Only fish explained these population changes because alternative factors such as drying were not significant. More catastrophically, fish introductions occurred in habitats known to support the largest populations of newts and even some endemic subspecies. If management and legislative measures are not taken to stop fish stocking, protect paedomorphs as conservation units at national and international levels, and restore natural habitats, all the largest paedomorphic populations may disappear in the near future. Their disappearance would represent a loss of one of the rare, fascinating examples of intraspecific heterochrony. [less ▲]

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See detailEffect of water temperature on the courtship behavior of the Alpine newt Triturus alpestris
Denoël, Mathieu ULg; Mathieu, Maryève; Poncin, Pascal ULg

in Behavioral Ecology and Sociobiology (2005), 58(2), 121-127

Temperature is expected to have an effect on the behavioral patterns of all organisms, especially ectotherms. However, although several studies focused on the effect of temperature on acoustic displays in ... [more ▼]

Temperature is expected to have an effect on the behavioral patterns of all organisms, especially ectotherms. However, although several studies focused on the effect of temperature on acoustic displays in both insects and anurans, almost nothing is known about how environmental temperature may affect ectotherm visual courtship displays and sexual performance. The purpose of this study was to determine the effect of environmental temperature on the sexual behavior of Alpine newts (Triturus alpestris). We subjected T. alpestris to two different temperatures in controlled laboratory conditions. Temperature had a major effect on both male and female behaviors: at low temperature, the frequencies of several displays, including tail-raising during sperm deposition, are lowered. This variation is caused indirectly by temperature because it is due to female responsiveness, which is temperature-dependent. However, the fanning movement of the male's tail during its main courtship display is independent of female behavior: at lower temperatures, the tail beats at a lower rate, but for a longer time. The similar reproductive success (i.e. sperm transfer) at the two temperature ranges indicates that breeding in cold water is not costly but instead allows males and females to mate early in the season. This is particularly adaptive because, in many habitats, the reproductive period is shortened by drying or freezing conditions, which may impair survival of branchiate offspring. This study also demonstrates the necessity of considering environmental parameters when modeling optimality and characteristics of ectotherm behaviors. [less ▲]

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See detailFish introduction is a major cause of paedomorphosis extinction in European newts (Triturus spp.)
Džukić, Georg; Ćirović, Ruža; Denoël, Mathieu ULg et al

in Froglog (2005), 69

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See detailEvolutionary ecology of facultative paedomorphosis in newts and salamanders
Denoël, Mathieu ULg; Joly, Pierre; Whiteman, Howard H.

in Biological Reviews (2005), 80(4), 663-671

Facultative paedomorphosis is an environmentally induced polymorphism that results in the coexistence of mature, gilled, and fully aquatic paedomorphic adults and transformed, terrestrial, metamorphic ... [more ▼]

Facultative paedomorphosis is an environmentally induced polymorphism that results in the coexistence of mature, gilled, and fully aquatic paedomorphic adults and transformed, terrestrial, metamorphic adults in the same population. This polymorphism has been of interest to scientists for decades because it occurs in a large number of caudate amphibian taxa as well as in a large diversity of habitats. Numerous experimental and observational studies have been conducted to explain the proximate and ultimate factors affecting these heterochronic variants in natural populations. The production of each alternative phenotype is based on a genotype x environment interaction and research suggests that differences in the environment can produce paedomorphs through several ontogenetic pathways. No single advantage accounts for the maintenance of this polymorphism. Rather, the interplay of different costs and benefits explains the success of the polyphenism across variable environments. Facultative paedomorphosis allows individuals to cope with habitat variation, to take advantage of environmental heterogeneity in the presence of open inches, and to increase their fitness. This process is expected to constitute a first step towards speciation events, and is also an example of biodiversity at the intraspecific level. The facultative paedomorphosis system is thus ripe for future studies encompassing ecology, evolution, behaviour, endocrinology, physiology, and conservation biology. Few other systems have been broad enough to provide varied research opportunities on topics as diverse as phenotypic plasticity, speciation, mating behaviour, and hormonal regulation of morphology. Further research on facultative paedomorphosis will provide needed insight into these and other important questions facing biologists. [less ▲]

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See detailConsequences of fish introductions on paedomorphic newts (Triturus alpestris and T. helveticus)
Denoël, Mathieu ULg; Dzukic, Georg; Kalezic, Milos

Poster (2005)

Fish stocking is largely recognized as a major thread to amphibian populations. Although it acts at a local level, it is widespread at a world scale. Despite this good knowledge, the effect of fish on ... [more ▼]

Fish stocking is largely recognized as a major thread to amphibian populations. Although it acts at a local level, it is widespread at a world scale. Despite this good knowledge, the effect of fish on alternative phenotypes has only been described in a few local studies. Our aim was to report on the loss of intraspecific heterochrony as a loss to diversity in determining the consequences of fish introductions on paedomorphs (morphs retaining gills at the adult stage) of two European species of newts. We surveyed almost all the main known paedomorphic populations of the Alpine (Triturus alpestris) and palmate (T. helveticus) newts, which all but one initially occupied fishless ponds and lakes in France, Italy, Slovenia, Bosnia, Montenegro, and Greece. Exotic fish were found in almost half of the studied aquatic habitats. Introductions involved several ornamental and large predatory species of fish. At all sites, in which fish were introduced, paedomorphs disappeared and metamorphs declined. The largest known populations of newts, including some endemic subspecies, were concerned. If measures are not taken to stop fish stocking, protect paedomorphs as conservation units, and restore natural habitats, all the largest paedomorphic populations may disappear in the near future. [less ▲]

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See detailOptimality of feeding on land versus in water in juvenile Alpine newts (Triturus alpestris veluchiensis)
Denoël, Mathieu ULg

Poster (2005)

Most newts experience both terrestrial and aquatic environments during their adult life. A large number of studies explored the feeding habits in the aquatic habitat while very few focused on the ... [more ▼]

Most newts experience both terrestrial and aquatic environments during their adult life. A large number of studies explored the feeding habits in the aquatic habitat while very few focused on the terrestrial component and none compared the two systems within a single population. The aim of this study was to find out which foraging tactic is the most successful in terms of energy intake. To this end, I analysed the feeding habits of metamorphosed juveniles in the Alpine newt inhabiting a Greek alpine lake and its surrounding lands. The diet reflected the range of prey available in the two habitats, but invertebrates, which fell on the water surface, were also ingested by aquatic newts. These two lifestyles had different energy outcomes because the highest number of terrestrial invertebrates taken in the terrestrial habitat than in the aquatic one provided higher energy gains to terrestrial juveniles. However, different mortality rates between habitats (highest probability of freezing risk on high-elevated lands than in deep waters) and an expected lower energy intake on land when air temperature is low could explain the persistence of the aquatic foraging tactic in the population. [less ▲]

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See detailAre cannibalistic morphs of the tiger salamander obligatory cannibals?
Denoël, Mathieu ULg; Whiteman, Howard; Wissinger, Scott

Conference (2005)

Tiger salamanders exhibit alternative trophic morphologies, with cannibals developing a larger head and longer teeth than typical larvae. Resource partitioning is known between morphs, with cannibal ... [more ▼]

Tiger salamanders exhibit alternative trophic morphologies, with cannibals developing a larger head and longer teeth than typical larvae. Resource partitioning is known between morphs, with cannibal morphs usually foraging on conspecifics and rarely on small organisms. Our aim was to determine whether the cannibal and typical morphs shift their diets across time and particularly whether conspecifics are necessarily the main prey of cannibals and plankton the primary prey of typicals. We found that only the cannibal morph foraged on conspecifics, but not all the time. Cannibalism typically occurred only early after the ontogenetic divergence between morphs. Cannibals shifted their diet later in the summer to plankton, and this ontogenetic shift led to dietary overlap with the typical morph. In contrast to other studies, our findings suggest that the cannibal morphology actually allows the consumption of a larger variety of prey, rather than specialization on specific resources (i.e., conspecifics). The outcomes of the cannibalistic ontogenetic pathway include a higher biomass intake from food and a larger size than typicals. From a foraging perspective, the cannibalism pathway is clearly advantageous over the typical morphology. However, the increased diet breadth of cannibal morphs found in this study suggests that the maintenance of the polyphenism is more complex than has previously been suggested. [less ▲]

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See detailCourtship behaviour at low and high water temperatures in the Alpine newt
Denoël, Mathieu ULg; Mathieu, Maryève; Poncin, Pascal ULg

Poster (2005)

Environmental factors are known to have a major effect on behavioral patterns of organisms. Among these factors, temperature particularly affects ectotherms. However, although many studies focused on ... [more ▼]

Environmental factors are known to have a major effect on behavioral patterns of organisms. Among these factors, temperature particularly affects ectotherms. However, although many studies focused on acoustic communication, the effect of environmental temperature on visual courtship displays and sexual performance has been little explored. The aim of this work was to determine the effect of temperature on the sexual behaviour of the Alpine newt Triturus alpestris in controlled laboratory conditions. Temperature had a major effect on the two sexes: at low temperatures, the frequencies of several displays, including sperm deposition, is lowered. This variation is in fact caused by the female responsiveness, which is temperature-dependent. However, some other behaviours, such as the fanning movement of the male’s tail (i.e., the main courtship display) are directly dependent on temperature: at lower temperatures, the tail beats at a lower rate but for a longer time. The similar reproductive success at the two temperatures indicates that breeding in cold water is not necessarily costly. It allows males and females to mate early in the season. This is particularly adaptive because, in many habitats, the reproductive period is shortened by drying or freezing conditions which may impair survival of branchiate offspring. [less ▲]

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See detailFeeding performance in heterochronic alpine newts is consistent with trophic niche and maintenance of polymorphism
Denoël, Mathieu ULg

in Ethology (2004), 110(2), 127-136

The feeding performances of two heterochronic morphs of the Alpine newt Triturus alpestris were investigated in laboratory experiments. Although both morphs are able to feed in the aquatic habitat, the ... [more ▼]

The feeding performances of two heterochronic morphs of the Alpine newt Triturus alpestris were investigated in laboratory experiments. Although both morphs are able to feed in the aquatic habitat, the hydrodynamics of prey capture differ between morphs. In paedomorphs water sucked with prey is expelled behind the mouth through gill bars. In metamorphs, water is expelled by the mouth as gill slits are closed. Feeding performance was better in paedomorphs than in metamorphs when foraging on aquatic crustaceans, but paedomorphs were less successful when foraging on terrestrial invertebrates caught at the water surface. These differences in prey capture success related to prey type allow the two morphs to use specific resources in their aquatic habitat. These results are consistent with previous studies that showed diet differentiation between morphs in natural populations. Such resource partitioning is a factor favouring the maintenance of facultative paedomorphosis in natural populations. [less ▲]

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See detailTerrestrial versus aquatic foraging in juvenile Alpine newts (Triturus alpestris)
Denoël, Mathieu ULg

in Ecoscience (2004), 11(4), 404-409

Many species of newts and salamanders forage in both terrestrial and aquatic environments during their life. However, the relative benefits of the two foraging patterns remain unknown because all previous ... [more ▼]

Many species of newts and salamanders forage in both terrestrial and aquatic environments during their life. However, the relative benefits of the two foraging patterns remain unknown because all previous studies have focused on only one habitat. The aim of this study was to find out which foraging tactic is the most successful in terms of energy intake. To this end, I analyzed trophic habits in metamorphosed juveniles in the Alpine newt, Triturus alpestris veluchiensis, inhabiting an alpine lake (Drakolimni) and the surrounding lands (Tymphi Mountains, northern Greece). The diet of the newts reflected the range of prey available in the two habitats, but aquatic newts also foraged on invertebrates that fell on the water surface. The two lifestyles have different energy outcomes. Terrestrial invertebrates provided high energy gains mainly to terrestrial juveniles because of the low number of this prey type in the lake. However, terrestrial juveniles are expected to suffer higher mortality (freezing on land is more probable than in deep waters) and a lower energy intake when air temperature is low, i.e., the main pattern in high-elevation sites, except during mid-summer. Persistence of the aquatic foraging tactics in the population may depend on a trade-off between costs and benefits. [less ▲]

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See detailDistribution and characteristics of aquatic habitats of newts and yellow-bellied toads in the district of Ioannina (Epirus, Greece)
Denoël, Mathieu ULg

in Herpetozoa (2004), 17(1/2), 49-64

The study describes the aquatic habitats and distribution of Triturus alpestris veluchiensis Wolterstorff 1935, T. carnifex macedonicus (Karaman, 1922), T. vulgaris graecus (Wolterstorff, 1905) and ... [more ▼]

The study describes the aquatic habitats and distribution of Triturus alpestris veluchiensis Wolterstorff 1935, T. carnifex macedonicus (Karaman, 1922), T. vulgaris graecus (Wolterstorff, 1905) and Bombina variegata scabra (Küster, 1843) in the district (“nomos”) of Ioannina, Northern Greece. Bombina variegata was found to be the most common species, followed by T. alpestris and T. carnifex while T. vulgaris seemed to be rare. The four taxa differed in habitat use and geographic distribution. Records of T. alpestris were limited to the highest sites in the north and east of the district. This species inhabited alpine lakes, but also smaller habitats such as drinking troughs and ponds. Four populations contained paedomorphic individuals. Triturus vulgaris appeared to be restricted to low altitude sites in the centre of the district where it lived in reservoirs, watering basins and drinking troughs. Triturus carnifex and B. variegata had a wider distribution and occupied a broader spectrum of habitats. Bombina variegata was the only species studied which lived in running waters (small brooks). Neither newts nor yellow-bellied toads were found in large rivers and lakes. In the district of Ioannina both habitat variety and distribution range of newts and Yellow-bellied Toads turned out to be greater than previously known. Alpine lakes containing very large populations of paedomorphic individuals should be protected given the rarity of the phenomenon. [less ▲]

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See detailTrophic specialisations in alternative heterochronic morphs
Denoël, Mathieu ULg; Schabetsberger, Robert; Joly, Pierre

in Naturwissenschaften (Die) (2004), 91(2), 81-84

Polymorphisms are suspected of reducing competition among conspecifics in heterogeneous environments by allowing differential resource use. However the adaptive significance of alternative morphs has been ... [more ▼]

Polymorphisms are suspected of reducing competition among conspecifics in heterogeneous environments by allowing differential resource use. However the adaptive significance of alternative morphs has been poorly documented. The aim of this study is to determine food partitioning of two heterochronic morphs of the Alpine newt, Triturus alpestris, in mountain lakes. The morphs differ in the functional morphology of their feeding apparatus. Only paedomorphs are able to expel water during prey suction behind the mouth through gill slits. We observed a substantial trophic differentiation between morphs in all lakes. Paedomorphs preyed mainly on plankton, whereas metamorphs foraged on terrestrial invertebrates that fell upon the water surface. This resource partitioning may facilitate the coexistence of the alternative morphs in lakes devoid of vertebrate competitors. Food diversity may thus favour the evolutionary maintenance of facultative polymorphism in natural populations. [less ▲]

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See detailRépartition, habitat et conservation des amphibiens du Pays de Herve
Denoël, Mathieu ULg

in Bulletin de la Société Herpétologique de France (2004), 111-112

The knowledge of distribution and ecological determinants of species is a prerequisite to their conservation at a time where declines are generalized at a world scale. The aim of this study is to ... [more ▼]

The knowledge of distribution and ecological determinants of species is a prerequisite to their conservation at a time where declines are generalized at a world scale. The aim of this study is to characterize these topics to discuss the status of amphibian species in Pays de Herve, an area which is representative of hedged farmland regions and their evolution toward a landscape homogenization. On more than four hundreds ponds surveyed, 72% contained amphibians. All Walloon amphibian species (except those recently disappeared), were present but some were rare. The natterjack toad and the crested newt are the two most threatened species in a close future, but almost all species are threatened with large population decreases. The destruction and abandon of cattle ponds is the primary factor of decline of amphibians in Pays de Herve, but other factors such as fish introduction and water pollution have also a negative impact in decreasing biodiversity in favour of less specialized species. Management and conservation measures should be taken as soon as possible to stop or at least slow down the current process. [less ▲]

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See detailResource partitioning in two heterochronic populations of Greek Alpine newts, Triturus alpestris veluchiensis
Denoël, Mathieu ULg; Schabetsberger, R.

in Acta Oecologica: International Journal of Ecology (2003), 24(1), 55-64

Current ecological models suggest that the maintenance of trophic polymorphisms is favoured by a different resource use in alternative morphs. Facultative paedomorphosis in newts is an example of ... [more ▼]

Current ecological models suggest that the maintenance of trophic polymorphisms is favoured by a different resource use in alternative morphs. Facultative paedomorphosis in newts is an example of phenotypic variation as paedomorphs retain morphological larval traits, such as gills and gill slits. The aim of this study was to find out whether heterochronic morphs occupy particular micro-habitats and focus on specific prey items. Resource partitioning was found between morphs. It concerns mainly food selection with paedomorphs preying more on plankton and less on terrestrial invertebrates than metamorphs. Some habitat specializations were also found with metamorphs being more abundant at the water surface than paedomorphs. Diel variation in habitat use of the two different morphs was minimal. Polymorphism allows Alpine newts to exploit the different resources in the lakes in order to minimize intraspecific competition, but the extent of resource partitioning depends on habitat characteristics. (C) 2003 Editions scientifiques et medicales Elsevier SAS. All rights reserved. [less ▲]

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See detailEffect of rival males on the courtship of paedomorphic and metamorphic Triturus alpestris (Amphibia : Salamandridae)
Denoël, Mathieu ULg

in Copeia (2003), 2003(3), 618-623

Current theories on the alternative mating tactics suppose that individuals may opt for particular behavioral patterns depending of their morphological status. Facultative paedomorphosis in newts and ... [more ▼]

Current theories on the alternative mating tactics suppose that individuals may opt for particular behavioral patterns depending of their morphological status. Facultative paedomorphosis in newts and salamanders is a suitable process to explore this question because it implies the coexistence of two different morphological morphs differing by the presence of gills and epigamic traits. The aim of this study was to find out whether paedomorphs and metamorphs use similar tactics to attract mates in the presence of a rival and whether there are differences in sexual activity and success between alternative morphs. Sexual interactions in triadic encounters were staged and analyzed in a standardized experimental design. The two kinds of males did not differ in terms of sexual activity, spermatophore deposition or female responsiveness. Both rival paedomorphic and metamorphic males exhibited sexual interference, but in most encounters, intruders just disturbed the courting pair. Sperm transfer success was lower in triadic encounters than in dyadic encounters. These results illustrate that intermorph breeding also occurs in the presence of competitors but that the success rate of the newts is considerably decreased in such competitive situations. Moreover, newts do not use alternative reproductive tactics depending on their status (i.e., paedomorph or metamorph). [less ▲]

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See detailTrophic habits and aquatic microhabitat use in gilled immature, paedomorphic and metamorphic Alpine newts (Triturus alpestris apuanus) in a pond in central Italy
Denoël, Mathieu ULg; Andreone, F.

in Belgian Journal of Zoology (2003), 133(2), 95-102

Current evolutionary models suggest that the presence of heterogeneous habitats favours the evolution of polymorphisms. In such cases, alternative phenotypes can coexist because they use different ... [more ▼]

Current evolutionary models suggest that the presence of heterogeneous habitats favours the evolution of polymorphisms. In such cases, alternative phenotypes can coexist because they use different resources. Facultative paedomorphosis is a heterochronic polymorphism in which a morph - the paedomorph - retains larval traits during the adult stage while the other morph - the metamorph - is fully metamorphosed. The aim of this study was to determine the microhabitat use and the diet of Alpine newt paedomorphs, metamorphs and immatures (Triturus alpestris apuanus) coexisting in a small pond in Tuscany, central Italy, i.e. in a habitat where dimorphism is not expected. Although the two adult morphs do not use exactly the same resources, resource partitioning was weaker than in deep Alpine lakes. Nevertheless, the diet of immature gilled newts (larvae) differed from that of adults (metamorphs and paedomorphs). While the larvae eat a large number of planktonic organisms, the adults focus on insect larvae and newt eggs. The differences in resource use favour the coexistence of aquatic juveniles and adults. In the studied pond, facultative paedomorphosis was previously shown to be favoured by a precocious maturity of the paedomorphs. This study shows that the coexistence of paedomorphs and metamorphs may also be supported by some dietary and spatial segregation, although any advantages gained by this pattern are rather limited in the adult stage. [less ▲]

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See detailHow do paedomorphic newts cope with lake drying?
Denoël, Mathieu ULg

in Ecography (2003), 26(4), 405-410

Paedomorphosis, in which adult individuals retain larval traits, is widespread in newts and salamanders. Most evolutionary models predict the maintenance of this life-history trait in favourable aquatic ... [more ▼]

Paedomorphosis, in which adult individuals retain larval traits, is widespread in newts and salamanders. Most evolutionary models predict the maintenance of this life-history trait in favourable aquatic habitats surrounded by hostile terrestrial environments. Nevertheless, numerous ponds inhabited by paedomorphic individuals are unpredictable and temporary. In an experimental framework, I showed that paedomorphic newts were able to metamorphose and thus survive in the absence of water. However, the mere decrease of water level or the life space do not seem to induce metamorphosis in paedomorphs. On the contrary, drying up induces almost all individuals to move on land and after that to colonize other aquatic sites located nearby. Such terrestrial migrations allow survival in drying conditions without metamorphosis as long as the distances of terrestrial migration are short. These results are consistent with the presence of paedomorphs in drying ponds and are in favor of classic optimality models predicting metamorphosis in unfavorable environments. [less ▲]

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