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See detailAmphibia-Reptilia: Editorial report 2005-2007
Denoël, Mathieu ULg

Conference (2007, September 22)

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See detailLandscape-level thresholds and newt conservation
Denoël, Mathieu ULg; Ficetola, G. Francesco

in Ecological Applications (2007), 17(1), 302-309

Ecological thresholds are defined as points or zones at which a rapid change occurs from one ecological condition to another. The existence of thresholds in species - habitat relationships has important ... [more ▼]

Ecological thresholds are defined as points or zones at which a rapid change occurs from one ecological condition to another. The existence of thresholds in species - habitat relationships has important implications for management, but the lack of concordance across studies and the wide range of methods used make generalizations difficult. We used two different statistical methods to test for the existence of thresholds for both individual species and the whole community, using three newt species as models. Based on a sample of 371 ponds, we found significant thresholds for both landscape configuration and composition. These were for the relationships between distance to forest and occurrence of Triturus alpestris and T. helveticus, and forest and crop cover and T. helveticus. Variability in the location of thresholds observed for the different species in this study caution against their use at the community level. Future studies should be based on the identification and assessment of thresholds for targeted species. Thresholds can be a useful concept from which tools may be developed to focus conservation effort for threatened species and their habitats. [less ▲]

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See detailForaging tactics in alternative heterochronic salamander morphs: trophic quality of ponds matters more than water permanency
Denoël, Mathieu ULg; Whiteman, Howard H.; Wissinger, Scott A.

in Freshwater Biology (2007), 52(9), 1667-1676

1. In lentic freshwater habitats, the composition of animal assemblages shifts along a gradient from temporary to permanent basins. When habitats with different degrees of permanence are at the scale of ... [more ▼]

1. In lentic freshwater habitats, the composition of animal assemblages shifts along a gradient from temporary to permanent basins. When habitats with different degrees of permanence are at the scale of the home range of species, they constitute alternatives in terms of energy acquisition through feeding. 2. In this context, previous studies showed an advantage of metamorphic over paedomorphic tiger salamanders (Ambystoma tigrinum) in temporary ponds which are only available to metamorphs. The aim of this study was to establish whether salamanders obtain similar benefits in ponds that do not differ in water permanence and whether salamanders shifted from detrimental to advantageous ponds. To this end, we determined the feeding habits, body condition and movement patterns of the two morphs in a complex of four permanent and four temporary ponds. 3. Consistent with previous studies, metamorphs consumed higher-quality diets than paedomorphs in term of energy intake. However, these differences occurred because metamorphs consumed fairy shrimp in a single temporary pond. Individual movement patterns confirmed that most of the metamorphs used different aquatic habitats both within and between years and that most of them moved from permanent ponds for breeding towards the most profitable temporary pond in terms of foraging. 4. These results indicate that habitat selection by salamanders is optimal in term of energy intake in metamorphs that use high quality ponds independently of hydroperiod. It seems that both spatial and temporal variation can influence the relative foraging success of each morph. [less ▲]

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See detailMorph switching in a dimorphic population of Triturus alpestris (Amphibia, Caudata)
Denoël, Mathieu ULg; Lena, Jean-Paul; Joly, Pierre

in Evolutionary Ecology (2007), 21(3), 325-335

The usual life cycle of Alpine newts comprises an aquatic larval stage and a terrestrial juvenile and adult stage. However, some populations differ from this pattern in exhibiting facultative ... [more ▼]

The usual life cycle of Alpine newts comprises an aquatic larval stage and a terrestrial juvenile and adult stage. However, some populations differ from this pattern in exhibiting facultative paedomorphosis where some individuals reach sexual maturity while retaining larval traits such as gills and gill slits. While paedomorphic newts can, in some circumstances, initiate metamorphosis, once a newt has commenced metamorphosis, the state is irreversible. Because the frequency of this switching from one morph to the other has never been quantified in the wild, we attempted to estimate switching rate and survival by carrying out a 3-year monitoring survey of a population inhabiting an alpine lake. While morph switching did occur in this population, it involved a relatively low proportion of the paedomorphs (approx. 12%), suggesting that metamorphosis is not favoured in the study population. The hypothesis of paedomorphic advantage was not supported since neither survival nor body condition differed between morphs. The ontogenetic pathway of wild Alpine newts is thus characterised by two forks in the developmental pathway. The first occurs during the larval stage (metamorphosis vs. paedomorphosis), and the second occurs in paedomorphic adults (switching for metamorphosis vs. continuation of the paedomorphic lifestyle). Such a two-level decision process may allow individuals to cope with environmental uncertainty. [less ▲]

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See detailPriority areas of intraspecific diversity: Larzac, a global hotspot for facultative paedomorphosis in amphibians
Denoël, Mathieu ULg

in Animal Conservation (2007), 10(1), 110-116

Although the designation of biodiversity hotspots is a valuable tool to improve conservation efforts, this is a concept primarily based on species diversity. In consequence, another component of ... [more ▼]

Although the designation of biodiversity hotspots is a valuable tool to improve conservation efforts, this is a concept primarily based on species diversity. In consequence, another component of biodiversity, adaptive variation, is often ignored in conservation and to my knowledge no attempt has been made to identify hotspots of remarkable intraspecific patterns. My aim was to focus on the process of facultative paedomorphosis (i.e. the retention of larval traits such as gills in adult variants), a rare developmental pathway. One hundred and seventy-four ponds were inventoried in Larzac (France) to determine the distribution and abundance of paedomorphic palmate newts Triturus helveticus (Amphibia, Caudata) and to compare these results with the current distribution of paedomorphs in this and other species. During this study, paedomorphic newts were found in 46 ponds, 32 of which were described here for the first time. Seventy-nine per cent of known paedomorphic populations of this species were found there, whereas this area covers only 0.5% of the distribution area of the species. This represents the highest known density of facultatively paedomorphic populations, all species being considered. Because these populations face a high threat of disappearance, Larzac should be designated as an intraspecific biodiversity hotspot in order to protect adaptive intraspecific variation. Future conservation-oriented work should focus not only on species distributions but also on phenotypically diverse but spatially localized variation. [less ▲]

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See detailEditorial Report 2006
Denoël, Mathieu ULg

in Amphibia-Reptilia (2007), 28(3), 455-456

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See detailLe Triton palmé, Triturus helveticus (Razoumowski, 1789)
Denoël, Mathieu ULg

in Jacob, Jean-Paul; Percsy, Christiane; de Wavrin, Hellin (Eds.) et al Amphibiens et Reptiles de Wallonie (2007)

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See detailLe Triton crêté, Triturus cristatus (Laurenti, 1768)
Jacob, Jean-Paul; Denoël, Mathieu ULg

in Jacob, Jean-Paul; Percsy, Christiane; de Wavrin, Hellin (Eds.) et al Amphibiens et Reptiles de Wallonie (2007)

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See detailLe Crapaud calamite, Bufo calamita Laurenti, 1768
Graitson, Eric ULg; Denoël, Mathieu ULg

in Jacob, Jean-Paul; Percsy, Christiane; de Wavrin, Hellin (Eds.) et al Amphibiens et Reptiles de Wallonie (2007)

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See detailLe Triton ponctué, Triturus vulgaris (Linnaeus, 1758)
Denoël, Mathieu ULg

in Jacob, Jean-Paul; Percsy, Christiane; de Wavrin, Hellin (Eds.) et al Amphibiens et Reptiles de Wallonie (2007)

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See detailLe Triton alpestre, Triturus alpestris (Laurenti, 1768)
Denoël, Mathieu ULg

in Jacob, Jean-Paul; Percsy, Christiane; de Wavrin, Hellin (Eds.) et al Amphibiens et Reptiles de WAllonie (2007)

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See detailAmphibiens et Reptiles de Wallonie
Jacob, Jean-Paul; Percsy, Christiane; de Wavrin, Hellin et al

Book published by Aves-Raînne et Centre de Recherche de la Nature, des Forêts et du Bois (MRW - DGRNE) (2007)

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See detailL’évolution du peuplement herpétologique en Région wallonne (Belgique)
Jacob, Jean-Paul; Percsy, Christiane; De Wavrin, Hellin et al

Conference (2007)

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See detailEcological thresholds and estimates of breaking points in newt populations: a useful tool to categorise habitat use and apply conservation measures
Denoël, Mathieu ULg; Ficetola, Gentile

Poster (2007)

Ecological thresholds are defined as points at which a rapid change occurs from one ecological condition to another. Their determination in species–habitat relationships has important implications because ... [more ▼]

Ecological thresholds are defined as points at which a rapid change occurs from one ecological condition to another. Their determination in species–habitat relationships has important implications because they allow to understand ecological requirements of species and to provide efficient conservation measures. However, there is a lack of concordance across studies and this method was not yet applied to newts. In this study, we sampled 371 ponds to gather occurrence data on the palmate newt Triturus heveticus and the Alpine newt Triturus alpestris. We tested for the existence of significant thresholds for three variables: distance to forest, forest and crop covers. We found significant thresholds for both landscape configuration and composition, with relationships between distance to forest and occurrence of Triturus alpestris and T. helveticus, and forest and crop cover and T. helveticus. Both species require breeding ponds within a given distance from the forest, but T. helveticus is more dependent on forest availability than T. alpestris: its ecological threshold is located at lower distance from forest edge, and requires also higher values of forest cover. Crops have a negative influence on palmate newt distribution with a significant breaking point, but not for T. alpestris in the studied area. These results indicate that thresholds can be a useful concept from which tools may be developed. They are particularly pertinent to focus conservation effort for threatened species and their habitats as quantitative measures of the most required habitats for species can be obtained from statistically determined breaking points [less ▲]

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See detailMetamorphosis rate of paedomorphs in a natural newt population
Denoël, Mathieu ULg; Lena, J. P.; Joly, Pierre

Poster (2007)

Facultative paedomorphis is a developmental process in which larvae opt for metamorphosis before maturity or reach sexual maturity while retaining larval traits (e.g., gills). Although metamorphosis is ... [more ▼]

Facultative paedomorphis is a developmental process in which larvae opt for metamorphosis before maturity or reach sexual maturity while retaining larval traits (e.g., gills). Although metamorphosis is not reversible, the paedomorphic state is not a dead end as branchiate adults are able to metamorphose. However, the extent of this process has never been quantified in the wild. Our aim was then to estimate switching rate by carrying out a 3-year monitoring survey of a population of Alpine newts (Triturus alpestris) inhabiting an alpine lake. The data were analysed using a multi-state capture-recapture model. While morph switching did occur in this population, it involved only 12% of the paedomorphs each year (i.e., 17% of recaptured individuals), suggesting that metamorphosis was not favoured in this population during the study period. This rate is lower than in laboratory experiments during which newts from the same population were placed in water drying conditions, but as shown previously paedomorphs can avoid metamorphosis in migrating to permanent water bodies when their pond dries out. These results are in agreement with other studies showing an advantage of a dimorphism in heterogeneous habitats. The ontogenetic pathway of wild Alpine newts is thus characterised by two forks in the developmental pathway. The first occurs during the larval stage, and the second occurs in paedomorphic adults. Such a two-level decision process may allow individuals to cope with environmental uncertainty. This may be particularly adaptive as aquatic conditions can deteriorate over time as shown by yearly changes in body condition of newts [less ▲]

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