Mathieu Denoël – Research projects
Our research aims at determining the characteristics and more particularly the determinism of diversity patterns in amphibians in function of environmental changes. A special focus is given on phenotypic plasticity and polyphenisms, such as facultative paedomorphosis (retention of gills at the adult stage versus metamorphosis). We characterize the benefits of life in the aquatic and terrestrial environments in link with the evolution of simple and complex life cycles. The approach is multidisplinary in behavioural and evolutionary ecology but also in landscape ecology, demography and population dynamics, biogeography, morphology, and genetics. The study integrates lab experiments in controlled environments and field sampling and observations in a large range of habitats and geographic areas. Our research is not only fundamental but also embedded in a biological conservation framework to explain adaptation and decline of amphibians at the inter and intraspecific levels. In this perspective, we target on the effects of climate change (water availability) and the introduction of invasive species (fish and amphibians).
Main study species: Ambystoma tigrinum, Anguilla anguilla, Calotriton asper, Carassius auratus, Ceratophrys stolzmanni, Ichthyosaura alpestris, Lissotriton graecus, Lissotriton helveticus, Lissotriton vulgaris, Pelobates fuscus, Pelobates syriacus, Rana temporaria, Pelophylax ridibundus, Salamandra salamandra, Triturus cristatus, Triturus marmoratus.
Genetic and environmental determinism of metamorphosis
Metamorphosis is a developmental process which has both a genetic and environmental underpinning. Through experiments in controled conditions, we study the environmental drivers of the evolution of metamorphosis and paedomorphosis, with a special focus on drying, predation risk and density. We also evaluate the costs of phenotypic transition (metamorphosis). Finally, by a genetic (transcriptomic) approach, we aim at identifying key gene expressions and their regulatory pathways during life cycle shift.
Mechanisms of coexistence by trophic resource partitioning
Through traditional (stomach flushing) and modern (stable isotopes) techniques, we characterize food webs from producers to top-predators, specifically newts in unaltered freshwater habitats. We test hypotheses on the importance of trophic resource partitioning for species and phenotype coexistence (facultative paedomorphosis as a resource polyphenism). In addition to an in situ approach, we carry out experiments on feeding performance and optimal foraging in the lab.
Sex and sexual selection
Through laboratory experiments, we characterize morphology (secondary sexual traits), courtship behaviour and fitness of alternative phenotypes (paedomorphs versus metamorphs) to understand how sexual selection affects the evolution of facultative paedomorphosis. We also integrate the effects of the environmental background to determine the extent of conditional behavioural strategies.
On another hand, we test the importance of sex-specific payoffs on the evolution of polymorphisms such as facultative paedomorphosis. Specifically, we study varied responses, notably metamorphic ones, in both males and females through lab experiments and field surveys on populations of paedomorphs and metamorphs. Finally, we analyze the extent, direction and causes of sexual dimorphism.
Ecological correlates of species distribution at landscape scale
The distribution of organisms such as amphibians depends on environmental factors which are affected at an increasing rate because of anthropogenic pressures. We integrate landscape and climatic GIS data with local habitat features in multivariate analyses, taking benefit of the recent advances in statistics so to highlight the success of amphibians under varied environments but also to identify key variables in the persistence of metamorphosis versus paedomorphosis. This research topic is therefore at the interface between evolutionary and conservation ecology.
Dispersal and movement ecology
We apply varied tagging methods, including RFID telemetry (PIT-tags) to track individuals across time in their natural environment. This allows us to determine individual patterns of habitat use and dispersal and to link them with environmental features, sex and morphological traits. Therefore, we also identify personaly traits and dispersal syndromes. We give much emphasis on patterns of breeding site infidelity and avoidance of detrimental habitats. By unravelling the patterns and advantages of dispersal of metamorphosed phenotypes, we also get insight into the relative payoffs of metamorphosis versus paedomorphosis, the latter involving philopatry of the aquatic phenotypes.
Biogeography and diversity loss
We participate at different mapping projects and long term population surveys at both local and global (European) scale. These analyses give us the bases to highlight biodiversity loss through mesaures of amphibian declines. We focus mainly on hotspots of intraspecific diversity, i.e. in southern Europe where predominate rare phenotypes such as paedomorphs.
Distribution and effect of invasive species in freshwater habitats
Through field surveys, we determine the effect of alien fish introductions on the distribution and decline of newts, and specifically of a rare alternative phenotype, the paedomorph, which stays all year round in water due to retention of gills. We are also interested in the adapation of invasive species in their new environments. In order to understand the mechanisms by which introduced species can affect native communities, we identify food webs and quantify them through varied metrics and we also analyze the behavioural response of amphibians to the presence of invaders (micro-habitat choice and impact on fitness). Because are phenotypes sucha s paedomorphs are more thretened than metamorphs, we also compare the response of both morphs to invaders.
Developmental pathways: age, growth and morphology
By using skelotochronological techniques (age determination), internal and external morphological measurements, as well as in situ longitudinal surveys, we characterize and highlight the adaptations of developmental patterns of alternative phenotypes (for instance, neoteny versus progenesis) in varied environments.
Population genetics and phylogeography
With the help of genetic markers (microsats, mtDNA, SNPs), we depict population structure and phylogeographic patterns, and we quantify gene flow in varied environments. Therefore, we highlight clades and evolutionary significant units, a key point in intraspecific conservation biology. At the population scale, we focus on the genetic compatibility or isolation between alternative phenotypes, then depicting the nature of the polyphenism (facultative paedomorphosis). Finaly, the genetic approach makes it possible to identify alien invaders and their introgression (specifically in hybridogenetic marsh frogs).
Behavioural markers – video-tracking
We use and develop several ethometric techniques to quantify the behavioural response of fish and amphibian individuals in varied environmental contexts. In particular, we used automatised procedures, such as video-tracking to automatically track single or groups of individuals in space and across time, in experimental conditions. We also quantify sequences of complex behavioural patterns through a numerical approach. To this end, we use the latest software packages from Noldus (EthoVision and Observer).
Other research topics
We have also additional side projects on other organisms, such as fish and reptiles and we also study epigenetic mechanisms and emerging diseases.
Several of our research projects, specifically those that are multi-disciplinary and involving specific technological platforms (e.g. in genetics) are made possible through local and international collaborations.