Research
We work at the interface between physiology, performance, and behaviour, on topics traditionally contained in the field of physiological ecology, behavioural ecology, and quantitative genetics. We seek to understand how the ecological and evolutionary interactions between metabolism, performance, and behaviour can generate and maintain diversity in life-history strategies. We focus on the evolutionary and energetic consequences of variation in behavioural traits such as locomotor activity, exploration, aggressiveness, boldness, and food hoarding. We regularly study if and how behaviour and energy expenditure are influenced by factors that are environmental (e.g., air temperature), ecological (e.g., food abundance, parasites), individual (e.g., age, reproduction, stress response), genetic (e.g., genetic correlations with other traits), or phylogenetic. Major lines of research include: the “energetics of personality” and the “pace-of-life syndrome”, the physiological ecology of white-footed mice, the quantitative genetic architecture of complex traits, and performance trade-offs. We study individual variation in combination with comparative studies at higher levels of biological variation (populations, species), as it yields complementary insights into how energetics, performance, and behaviour interact through evolution.
Approaches
We combine field and laboratory studies because the mix between the ecological reality of field studies and the precision attained in the lab provides a better understanding of the causes and consequences of variation in energy expenditure. From time to time, we also gather data from the literature and use the comparative approach to test our hypotheses. We generally enjoy analysing data using statistical methods that take into account the relationship among study subjects, such at phylogenies and pedigrees.
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KeywordsAnimal model
Artificial selection Basal metabolic rate Behavioural ecology Daily energy expenditure Evolutionary physiology Hoarding behaviour Life history strategies Maximum metabolic rate Pace-of-life syndrome Parasites Pedigree Personality Performance Phylogeny Physiological ecology Quantitative genetics Reaction norm Resting metabolic rate Rodents Slow-fast continuum Thermal reaction norm |
Research topics
Energetics and Personality
This research lies at the interface between ecology, physiology, and behaviour. We seek to understand the causes and consequences of individual co-variation in physiology and behaviour, which may help understanding the fundamental factors that underlie slow-fast life-history strategies. The conceptualisation of the link between animal personality and energy metabolism (paper #8) generated multiple ideas as to how these traits should interact with each other. For example, it is highly intuitive to think that personality is related to energy expenditure and resting metabolic rate because it is costly to express behaviours such as exploration, boldness, and aggressiveness. It is also possible that physiological constraints related to energy expenditure limit behavioural plasticity through time and/or among situations, which may create evolutionary trade-offs. This is why it is crucial to integrate personality and metabolism within an evolutionary framework, which is what the “pace-of-life syndrome” concept attempts to do (paper #13). The linkages between energetics and personality can also be studied within the classic “morphology-performance-fitness” framework (paper #20). Indeed, the integration of performance traits within research on the energetics of personality fills an important logical gap within the “pace-of-life” syndrome concept.
Physiological Ecology of White-Footed Mice
We are conducting a long-term, individual-based study of white-footed mice (Peromyscus leucopus). White-footed mice use wood boxes as long-term nests or temporary resting places, which is very convenient to study how natural selection operates in the wild, because it allows quantifying litter size and survival. We installed 200 artificial nest boxes at different stations spaced 15-30 meters apart. Visiting these nest boxes provide us with information on mice sociability, litter composition, and kinship (i.e., maternity and paternity links) that could not be otherwise obtained. The study site is also equipped with hundreds of live traps set at regular 15 m intervals. Each mouse captured (either in a box or a trap) is permanently marked with ear tags and transported to an adjacent laboratory where we measure things like exploratory behaviour, basal metabolic rate, aerobic capacity, sprint speed, and grip strength. Each graduate student has a project targeting a specific research area/question/trait. Mice are relatively abundant and easy to catch, such that projects can reach large sample size within 1 or 2 field seasons (e.g., see papers #55 and #63). Over the years, the data quickly accumulate, allowing us to tackle increasingly complex questions.
the quantitative genetic architecture of complex traits
We use two main approaches to study the quantitative genetic architecture of metabolism and behaviour: artificial selection experiments and breeding designs.
Selection experiment on voluntary wheel running:
In collaboration with Ted Garland we use a large dataset data from a replicated artificial selection experiment in mice. We compiled the data from multiple generations of the experiment, which resulted in a dataset of behavioural measurements on ~40,000 pedigreed individuals. Such a massive and rich dataset allows us to tackle important evolutionary questions related to selection limits (paper #25), the effect of selection on the G-matrix (paper #39), and indirect genetic effects (paper #50). Overall, we have only scratched the surface of this dataset, and we are using this selection experiment to further understand the limits to evolutionary change, which is of crucial importance in light of several recent published cases of apparent “evolutionary stasis” in wild populations of vertebrates.
Breeding designs in insects:
We use our high-throughput respirometry system to measure CO2 production in hundreds of offspring individuals resulting from complex breeding designs, allowing us to estimate additive genetic variance in metabolic rate (e.g., paper #64) and its covariance with other traits (e.g., papers #54 and #64) and fitness (e.g., paper #59).
Selection experiment on voluntary wheel running:
In collaboration with Ted Garland we use a large dataset data from a replicated artificial selection experiment in mice. We compiled the data from multiple generations of the experiment, which resulted in a dataset of behavioural measurements on ~40,000 pedigreed individuals. Such a massive and rich dataset allows us to tackle important evolutionary questions related to selection limits (paper #25), the effect of selection on the G-matrix (paper #39), and indirect genetic effects (paper #50). Overall, we have only scratched the surface of this dataset, and we are using this selection experiment to further understand the limits to evolutionary change, which is of crucial importance in light of several recent published cases of apparent “evolutionary stasis” in wild populations of vertebrates.
Breeding designs in insects:
We use our high-throughput respirometry system to measure CO2 production in hundreds of offspring individuals resulting from complex breeding designs, allowing us to estimate additive genetic variance in metabolic rate (e.g., paper #64) and its covariance with other traits (e.g., papers #54 and #64) and fitness (e.g., paper #59).
Performance trade-offs
Both physiological and biomechanical theory predicts that certain performance traits will be negatively correlated. Therefore, why is it so hard to detect performance trade-offs at the whole-organismal level? Previous work showed that performance trade-offs emerge as expected after statistically adjusting for “quality”. This situation is similar to the “big houses big cars” model of life-history trade-offs, where allocation trade-offs occurring at the within-individual level can be masked by variation at the among-individual level. Although this idea was hotly debated in performance studies, none have partitioned the correlations at the among- vs within-individual levels. We conceptually developed an alternative scenario, the “sink or swim” scenario, where within-individual variation in condition can mask among-individual trade-offs (paper #44). Under the “sink or swim” scenario, using only the maximal performance for each individual (i.e., their “personal best”) can severely bias correlations and mask trade-offs. This idea is supported by data on decathletes and heptathletes (paper #45), who compete in multiple track and field events that are somewhat incompatible (e.g., having high upper body muscle mass will help in shot put, but hinder high jump). Yet, past studies on decathletes consistently failed to detect performance trade-offs and even commonly obtained counterintuitive positive correlations among performances across running, throwing, and jumping events because personal best scores were analysed. Instead of doing so, we used multivariate mixed models and found support for the “sink- or swim” scenario after controlling for various intrinsic (e.g., age, experience) and extrinsic (wind, temperature) factors (paper #45). We also found support for the “sink- or swim” scenario in wild white-footed mice (paper #55). We also analyzed performance data on Ironmen triathletes (paper #49) and elite swimmers (paper #67) to show shown that trade-offs can also occur at the within-individual, within race level. By making significant advances in our understanding of how trade-offs occur at the among- vs. within-individual levels, our work on performance trade-offs will inevitably help moving the field of performance trade-offs forward.
Other interesting topics
Climatic And Environmental Influences On Physiology And Behaviour
We also seek to understand the effects of climatic and environmental variation on physiology and/or behaviour. This broad research theme covers a large variety of topics and study models such as the effect of climate on hawks’ migrating behaviour (paper #1) and canids’ basal metabolic rate (paper #2), the effect of pulsed resources such as lemming peaks and goose eggs on the hoarding behaviour of arctic foxes (papers #3, 4, 6, and 7). During my PhD, I studied how resting metabolic rate changes as a function of resource pulses (paper #22) and number of parasites hosted in chipmunks (papers #11 and 18). I also found stabilizing selection on RMR and negative impacts of parasites on the growth rate and survival of juvenile chipmunks during a year of low food availability (paper #21). Recently, I showed how the effect of environmental temperature on RMR is different in species using torpor vs. species that don’t (paper #23). Work in collaboration with M. Humphries showed how an important but oft-overlooked phenomenon (i.e., the substitution of the heat required for thermoregulation by the heat produced by activity) may be an important determinant of the activity patterns and metabolic ecology of endotherms, and how it can generate commonly observed macro ecological and latitudinal patterns in energy expenditure (paper #15).
Thermal Reaction Norms Of Metabolism And Behaviour
We also work on individual variation in thermal sensitivity of metabolic, behavioural, and performance traits. It is widely known that metabolism doubles or triples in rate whenever temperature increases by 10ºC. The variation in thermal sensitivity among species and populations can sometimes be considerable and is often thought of as resulting from natural selection. However, the demonstration of heritable among-individual variation in thermal sensitivity necessarily precedes any attempt to determine its selective significance. Thus, one of our current research objectives is to quantify individual variation and heritability in thermal sensitivity for various metabolic, behavioural, and performance traits and the genetic correlations among them. Most quantifications of thermal reaction norms for physiological, behavioural, and performance traits are done in isolation from each other. As a result, we currently have little knowledge on whether thermal reaction norms of performance, reproductive success, behaviour, and metabolism are functionally integrated, despite the fact that this information is crucial to understand the evolutionary potential of a species to adapt to a gradual rise in temperature. In collaboration with Matthew Gifford, we showed the presence of significant individual variation in the thermal sensitivity of both standard and maximal metabolic rates in slimy salamanders (paper #30). In this study, we showed that the thermal sensitivities of standard and maximal metabolic rates were correlated at the among-individual level. The next step is to evaluate if different thermal reaction norms are heritable and genetically correlated, because this will determine the constraints on evolutionary responses to changing thermal regimes. Thus, this research topic unifies the two research themes above, as the general objective is to test whether a suite of metabolic, behavioural, and performance traits are functionally integrated along an environmental variable (temperature).
We also seek to understand the effects of climatic and environmental variation on physiology and/or behaviour. This broad research theme covers a large variety of topics and study models such as the effect of climate on hawks’ migrating behaviour (paper #1) and canids’ basal metabolic rate (paper #2), the effect of pulsed resources such as lemming peaks and goose eggs on the hoarding behaviour of arctic foxes (papers #3, 4, 6, and 7). During my PhD, I studied how resting metabolic rate changes as a function of resource pulses (paper #22) and number of parasites hosted in chipmunks (papers #11 and 18). I also found stabilizing selection on RMR and negative impacts of parasites on the growth rate and survival of juvenile chipmunks during a year of low food availability (paper #21). Recently, I showed how the effect of environmental temperature on RMR is different in species using torpor vs. species that don’t (paper #23). Work in collaboration with M. Humphries showed how an important but oft-overlooked phenomenon (i.e., the substitution of the heat required for thermoregulation by the heat produced by activity) may be an important determinant of the activity patterns and metabolic ecology of endotherms, and how it can generate commonly observed macro ecological and latitudinal patterns in energy expenditure (paper #15).
Thermal Reaction Norms Of Metabolism And Behaviour
We also work on individual variation in thermal sensitivity of metabolic, behavioural, and performance traits. It is widely known that metabolism doubles or triples in rate whenever temperature increases by 10ºC. The variation in thermal sensitivity among species and populations can sometimes be considerable and is often thought of as resulting from natural selection. However, the demonstration of heritable among-individual variation in thermal sensitivity necessarily precedes any attempt to determine its selective significance. Thus, one of our current research objectives is to quantify individual variation and heritability in thermal sensitivity for various metabolic, behavioural, and performance traits and the genetic correlations among them. Most quantifications of thermal reaction norms for physiological, behavioural, and performance traits are done in isolation from each other. As a result, we currently have little knowledge on whether thermal reaction norms of performance, reproductive success, behaviour, and metabolism are functionally integrated, despite the fact that this information is crucial to understand the evolutionary potential of a species to adapt to a gradual rise in temperature. In collaboration with Matthew Gifford, we showed the presence of significant individual variation in the thermal sensitivity of both standard and maximal metabolic rates in slimy salamanders (paper #30). In this study, we showed that the thermal sensitivities of standard and maximal metabolic rates were correlated at the among-individual level. The next step is to evaluate if different thermal reaction norms are heritable and genetically correlated, because this will determine the constraints on evolutionary responses to changing thermal regimes. Thus, this research topic unifies the two research themes above, as the general objective is to test whether a suite of metabolic, behavioural, and performance traits are functionally integrated along an environmental variable (temperature).
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