Dr. HUGO CAYUELA

I am broadly interested in population ecology, behavioral ecology and molecular ecology. I develop three main research themes: first, I focus on demographic processes and life history evolution. Second, I study the mechanisms underlying the evolution of dispersal and its consequences for population dynamics and genetics. Third, I investigate genetic, transcriptional and epigenetic bases of phenotype diversification in wild and experimental populations using next-generation sequencing technologies.

MY LATEST RESEARCH

Transcriptional and epigenetic bases of dispersal in a  protist

Dispersal designates the movement of an individual resulting in potential gene flow. Because it affects local colonization-extinction processes, gene flow among populations and phenotype composition within and between populations, dispersal is usually thought a central component involved in ecological and evolutionary processes. During the last decade, an increasing number of studies have proposed that inter-individual variation in dispersal-related traits may result from genetic variation. First, sequence polymorphism of candidate loci (e.g. the dopamine receptor D4 gene, DRD4; the serotonin transporter gene, SERT) has been associated with variation in phenotypic traits (e.g. exploratory behavior, harm avoidance behavior, foraging behavior) linked to dispersal capacity/propensity. Second, transcriptional analyses also revealed variation in gene expression profiles between dispersing and non-dispersing individuals. Yet, the regulation of gene expression by epigenetic factors and the contribution of such mechanisms to dispersal evolution are still poorly understood, although theoretical models show that transgenerational epigenetic factors may be involved in dispersal evolution. To fill this gap, in the present research project, we aim at investigating the role of epigenetic factors in the evolution of dispersal in the protist species Tetrahymena thermophila, which is a historical model organism in cell biology and epigenetics, and recently became a model species in the study of dispersal First, we use an artificial selection procedure to produce dispersing and non-dispersing phenotypes. Second, using NGS technologies, we investigate how the dispersing and non-dispersing phenotypes differ in terms of gene expression and methylation patterns.

Demographic response to patch destruction in an amphibian spatially structured population

Economic activities such as logging and mineral extraction can result in the creation of new anthropogenic habitats (e.g. temporary aquatic habitats) that may host specific biodiversity, including protected species. However, the legislation in many Western European countries requires the rehabilitation of ‘damaged’ areas following logging and mining operations, which can eliminate these early successional habitats. Conservation managers face a dilemma in these situations, but often lack knowledge about the impacts of environmental rehabilitation on the population dynamics of pioneer species and so are unable to take this into account in their actions. In a recent study, we investigated the demography of a spatially structured amphibian population that uses waterbodies created by logging activities as breeding sites. The species studied was the yellow-bellied toad (Bombina variegata), which is classified as endangered in Europe. Capture-Recapture multievent models revealed that dispersal not resulting from patch loss was relatively high and was sex-biased. They also revealed that patch destruction had a negative impact on adult survival. Moreover, metapopulation viability analyses showed that the frequency of patch destruction had a strong negative influence on the population growth rate. This impact was intensified if female fecundity was also affected. Our study also revealed that the detrimental impact of patch destruction could be reduced by certain practices – for example, reducing the frequency of destruction events – and thus its effect on demographic rates. In the light of these results, we recommend a number of conservation measures.

Kin selection, dispersal and population genetic structure in a lekking bird

Kin selection plays a critical role in the evolution of cooperative breeding systems. Hamilton theory states that an individual who improves the reproductive success of his relatives may increase his overall genetic contribution to future generations (i.e. inclusive fitness). A limited dispersal has been often proposed as putative mechanism for ensuring that cooperative behaviors are directed primarily towards closely related social partners. Moreover, population viscosity can be maintained if dispersers pay acute dispersal costs after settling into a new patch, limiting their contribution to local reproduction. In a recent study, we examined how kin-selected advantages and sex-specific dispersal costs shape relatedness and genetic spatial structure in the Western capercaillie (Tetrao urogallus). In females, our study revealed a weak spatial structure of relatedness. In addition, social and effective dispersal patterns were highly congruent. By contrast, we highlighted a strong spatial structure of relatedness in males, indicating a high level of viscosity in this sex. Our results also showed that social dispersal drastically outweighed effective dispersal. Overall, this indicates that males preferentially attend in leks composed of relatives and that dispersing males incurred high post-settlement costs when they arrive into a new lek (composed of unrelatives). These two mechanisms allow the retention of a sex-specific genetic structure through generations, males displaying higher genetic variability between leks than females.

Multiple density dependent processes shape amphibian population dynamics

Understanding the mechanisms that regulate the dynamics of spatially structured populations (SSPs) is a critical challenge for ecologists and conservation managers. Internal population processes such as births and deaths occur at a local level, while external processes such as dispersal take place at an inter-population level. At both levels, density dependence is expected to play a critical role. At a patch scale, demographic traits (e.g. survival, breeding success) and the population growth rate can be influenced by density either negatively (i.e. competition effect) or positively (i.e. Allee effect). At the scale of an SSP, although positive density-dependent dispersal has been widely reported, an increasing number of studies have highlighted negative density-dependent dispersal. While many studies have investigated the effects of density on population growth or on dispersal, few have simultaneously examined density-dependent effects at the scale of both the local population and of the entire SSP. In our study, we examined how density is related to demographic processes at both the pond level (survival and population growth) and at the SSP level (between-pond dispersal) in a pond-breeding amphibian, the great crested newt (Triturus cristatus). The study was based on 20 years of individual capture–recapture (CR) data gathered from an SSP made up of 12 experimental ponds. Our results found a positive density-dependent effect on survival and a negative density-dependent effect on departure. In addition, the findings indicated that density was negatively related to population growth in all 12 ponds. These results support the hypothesis that in SSPs, density may have multiple and contrasting effects on demographic traits and growth rates within local populations as well as on dispersal. Our study underlines the need to better understand how density dependence may influence potential trade-offs between life-history strategies and life-history stages.  

 

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