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See detailA multi-scale approach to facultative paedomorphosis of European newts (Salamandridae) in the Montenegrin karst: Distribution pattern, environmental variables, and conservation
Denoël, Mathieu ULg; Ficetola, Gentile Francesco; Cirovic, Ruza et al

in Biological Conservation (2009), 142(3), 509-517

Facultative paedomorphosis, a process in which newt larvae can opt for reproduction before or after metamorphosis, is geographically heterogeneous. Despite numerous ecological studies and recent evidence ... [more ▼]

Facultative paedomorphosis, a process in which newt larvae can opt for reproduction before or after metamorphosis, is geographically heterogeneous. Despite numerous ecological studies and recent evidence of declines in paedomorphic populations, however, no attempt to model environmental variables that explain the presence of paedomorphs has been made at a multi-scale level. Our aim was to fill this gap in studying three newt species (Lissotriton vulgaris, Mesotriton alpestris, and Triturus macedonicus) of the Montenegrin karst as model species. To this end, we used multivariate analysis on three scales of habitat: the breeding pond, the land use and the climatologic features. Results show that the study area is both an important hotspot for paedomorphosis and where intraspecific diversity is quickly disappearing (20-47% extirpation) because of fish introductions. Other habitat variables (water permanency, PH or the habitat origin) were shown to act on paedomorphosis but not consistently across species, confirming complexity of the evolutionary and ecological processes. This study appeals for more long-term and detailed landscape studies of polyphenisms, a neglected but promising topic, to better understand and protect alternative modes of development. Particularly, measures should be taken to identify hotspots of intraspecific diversity at a global scale and stop fish introductions before we reach a point of no-return. (C) 2008 Elsevier Ltd. All rights reserved. [less ▲]

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See detailSexual size dimorphism in the evolutionary context of facultative paedomorphosis: insights from European newts
Denoël, Mathieu ULg; Ivanovic, Ana; Dzukic, Georg et al

in BMC Evolutionary Biology (2009), 9

BACKGROUND:Sexual size dimorphism (SSD) is a key evolutionary feature that has been studied in many organisms. In a wide range of species, this pattern is more complex because of polymorphism within each ... [more ▼]

BACKGROUND:Sexual size dimorphism (SSD) is a key evolutionary feature that has been studied in many organisms. In a wide range of species, this pattern is more complex because of polymorphism within each sex. However, it is not known whether the magnitude and direction of SSD could be affected by alternative developmental trajectories within sexes. Our aim was to test whether an intrasexual polymorphism, facultative paedomorphosis (a process in which the development of somatic and gonadal tissues differs in alternative morphs), could affect SSD variation patterns in European newts. RESULTS:We report here the first evidence that SSD varies depending on the paedomorphic or metamorphic ontogenetic pathway. In species with a consistent female-biased SSD, paedomorphosis decreased the SSD level, but did not affect its direction. In species with moderate female-biased SSD or variable SSD patterns, paedomorphosis changed the magnitude, or both the magnitude and the direction, of SSD. CONCLUSIONS:Our study highlights the importance of developmental processes for shaping SSD patterns in populations in which contrasting life-history pathways evolved. European newts express different SSD patterns depending on their developmental pathway (i.e., metamorphosis versus paedomorphosis), as well as their species and population. These findings emphasize the importance of studying alternative morphotypes, which are found in a wide range of animal groups, to understand the evolution of SSD. [less ▲]

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See detailEcological thresholds: an assessment of methods to identify abrupt changes in species-habitat relationships
Ficetola, Gentile Francesco; Denoël, Mathieu ULg

in Ecography (2009), 32(6), 1075-1084

Habitat thresholds are usually defined as "points of abrupt change" in the species–habitat relationships. Habitat thresholds can be a key tool for understanding species requirements, and provide an ... [more ▼]

Habitat thresholds are usually defined as "points of abrupt change" in the species–habitat relationships. Habitat thresholds can be a key tool for understanding species requirements, and provide an objective definition of conservation targets, by identifying when habitat loss leads to a rapid loss of species, and the minimum amount of habitat necessary for species persistence. However, a large variety of statistical methods have been used to analyse them. In this context, we reviewed these methods and, using simulated data sets, we tested the main models to compare their performance on the identification of thresholds. We show that researchers use very different analytical tools, corresponding to different operational definitions of habitat thresholds, which can considerably affect their detection. Piecewise regression and generalized additive models allow both the distinction between linear and nonlinear dynamics, and the correct identification of break point position. In contrast, other methods such as logistic regression fail because they may incorrectly detect thresholds in gradual patterns, or they may over or underestimate the threshold position. In conservation or habitat modelling, it is important to focus efforts efficiently and the inappropriate choice of statistical methods may have detrimental consequences. [less ▲]

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See detailEcological modeling and paedomorphosis: a study case in Montenegrin newts
Denoël, Mathieu ULg; Ficetola, Gentile; Cirovic, Rusa et al

Poster (2009)

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See detailThe benefits of heterospecific oophagy in a top predator
Denoël, Mathieu ULg; Demars, Bertrand

in Acta Oecologica: International Journal of Ecology (2008), 34(1), 74-79

Oophagy is a behavioural pattern that has been found in a large variety of predator species in the animal kingdom. In contrast to other modes of feeding, it is peculiar in that it involves the detection ... [more ▼]

Oophagy is a behavioural pattern that has been found in a large variety of predator species in the animal kingdom. In contrast to other modes of feeding, it is peculiar in that it involves the detection, capture and ingestion of immobile prey. Several hypotheses have been proposed to explain the evolutionary origin and persistence of this pattern, but they have rarely been tested. The aim of this study was to compare the benefits of a heterospecific oophagous tactic over a non-oophageous diet in terms of biomass intake. To this end, stomach contents were gathered by flushing the stomachs of male and female Alpine newts (Mesotriton alpestris) found in forestry ruts (i.e. pools caused by traffic) during their reproductive period. Prey items were identified, classified into functional categories and their dry mass determined. Frog (Rana temporaria) eggs are valuable prey items that give a higher biomass intake to individuals foraging on them than on those relying on invertebrates. Both sexes of newts practice oophagy but frog eggs are a transient resource that is only available during a part of their aquatic phase. Consequently, the newts adjust their diet to invertebrate predation later in the season after the peak of the frogs' breeding season. Oophagy is thus facultative and not obligate in the study species. The correlated occurrence of prey and predator, similarities between frog eggs and mobile potential prey (tadpoles), and high resource intake are all in favour of the occurrence and persistence of an oophagous feeding tactic. (c) 2008 Elsevier Masson SAS. All rights reserved. [less ▲]

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See detailConservation of newt guilds in an agricultural landscape of Belgium: the importance of aquatic and terrestrial habitats
Denoël, Mathieu ULg; Ficetola, G. Francesco

in Aquatic Conservation (2008), 18(5), 714-728

1. Amphibians are declining worldwide in response to local and global pressures. Pond-breeding species are particularly vulnerable to environmental change because they rely on two components of the ... [more ▼]

1. Amphibians are declining worldwide in response to local and global pressures. Pond-breeding species are particularly vulnerable to environmental change because they rely on two components of the landscape: aquatic and terrestrial habitats. Agricultural practices are changing rapidly at world and local scales. As a consequence, farm ponds and their surrounding terrestrial landscapes will probably be affected. 2. This study investigated the main habitat determinants for the occurrence of four species of newts (genus Triturus) inhabiting the Pays de Herve, a rural area in Belgium. Newt occurrence was determined for 258 ponds and the effect of habitat on distribution determinants was evaluated using generalized linear models. 3. Newts were found in 42% of the ponds. Contrary to expectations, the distribution of newts was not positively associated with a high density of ponds. However, a low occurrence of newts and the low water depth of many ponds suggest a low quality of habitats. Proximity to forest, deep water, and an absence of fish in ponds are factors that significantly favour newts, but terrestrial habitat requirements vary among species. 4. These results indicate the necessity of maintaining both forest and meadow patches in close proximity to ponds inhabited by newts., and of controlling fish introduction in those ponds. These findings stress the importance of conservation and management of terrestrial and aquatic habitats for maintaining amphibian diversity. Copyright (c) 2007 John Wiley & Sons, Ltd. [less ▲]

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See detailEditorial Report 2007
Denoël, Mathieu ULg

in Amphibia-Reptilia (2008), 29(3), 455-456

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See detailStatus and causes of decline in heterochronic newts from Europe
Denoël, Mathieu ULg; Dzukic, Georg; Ficetola, Gentile et al

Conference (2008)

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See detailEffect of temperature increase on the courtship behavior and the fitness in the Palmate newt
Galloy, Valérie ULg; Lo Presti, Wendy; Denoël, Mathieu ULg

Poster (2008)

A trend in global warming is now undeniable. Increases of global temperatures have resulted in measurable shifts in the distribution, phenology and survival of some plant and animal species. However, the ... [more ▼]

A trend in global warming is now undeniable. Increases of global temperatures have resulted in measurable shifts in the distribution, phenology and survival of some plant and animal species. However, the mechanisms showing the link between global warming and declines remain unclear. The aim of this study was to examine whether courtship displays and fitness could be affected by a temperature increase. To this end, we compared the sexual behavior and egg-laying traits at naturally occurring temperatures (14 C, 18 C and 22 C) in palmate newts (Triturus helveticus). First, our results underline the importance of female role in the male courtships. The majority of male behaviors are affected by the female responsiveness, which is temperature dependent. They also show that water temperature increase has a negative effect on the fecundity of female newts. Females lay half as many eggs at high temperatures as they do at low temperatures and of these only one third hatch. The demonstration of such a detrimental effect shows that more experimental studies are required to understand the proximate mechanisms of global warming. [less ▲]

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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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