Raphaël Royauté | North Dakota State University (original) (raw)

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Papers by Raphaël Royauté

Despite recent progress in elucidating the genetic basis for behavioral variation, the effects of... more Despite recent progress in elucidating the genetic basis for behavioral variation, the effects of the developmental environment on the maintenance and generation of behavioral variation across multiple traits remain poorly resolved. We investigated how nutritional status during development affected behavioral variation and covariance between activity in an open field test and response to cues of predator presence in the house cricket (Acheta domesticus). We provided 98 juvenile crickets with either a high or low quality diet during development, throughout which we measured body mass, activity in a modified open-field, and response to predator excreta twice every week for 3 weeks. Diet quality affected growth rate but not average activity or response to cues of predator presence, nor the correlation between the 2. However, repeatability (τ) in response to cues of predator presence was reduced by 0.24 in individuals exposed to the high quality diet versus the low quality diet. Larger individuals also increased their response to predator cues when reared on a high quality diet, suggesting negative feedbacks between growth rate and antipredator behaviors. Our results also indicate that changes in the developmental environment are not sufficient to collapse behavioral syndromes, suggesting a genetic link between activity and predator cue response in house crickets, and that nutritional stress early in life can lead to more consistent behavioral responses when individuals faced predatory threats. Our results demonstrate that subtle differences in the quality of the environment experienced early in life can influence how individuals negotiate behavioral and life-history trade-offs later in life.

The pace-of-life hypothesis predicts that among-individual differences in behaviour should integr... more The pace-of-life hypothesis predicts that among-individual differences in behaviour should integrate with a wide variety of morphological, metabolic and life-history traits along a slow to fast pace-of-life continuum. Support for the pace-of-life hypothesis has been mixed, in part because most empirical tests have been conducted strictly at the phenotypic level and have thus conflated genetic and environmental sources of covariance among traits. In the present study, we tested the hypothesis that, ac- cording to the predictions of the pace-of-life hypothesis, body mass, routine metabolic rate, activity and exploratory propensity are positively integrated in the house cricket Acheta domesticus (Orthoptera: Gryllidae). Using modified open field behavioural tests and flow-through respirometry, we determined whether among-individual differences are correlated across morphology, behaviour and metabolism in 50 male house crickets. All traits were repeatable, but we found poor evidence for overall integration across traits. Instead we found evidence for modularity, with behavioural traits covarying independently from mass and routine metabolic rate. Modularity, like that found here between activity and exploratory propensity, has been suggested to facilitate adaptive evolutionary change by coupling functionally related traits into suites on which selection can act more rapidly.

Most taxa show consistent individual differences in behavior, a phenomenon often referred to as a... more Most taxa show consistent individual differences in behavior, a phenomenon often referred to as animal "personalities". While the links between individual personality and fitness have received considerable attention, little information is available on how animal personality impacts higher order ecological processes, such as community dynamics. Using a mesocosm experiment, we subjected a representative community of alfalfa pests to different compositions of personality types of the wolf spider Pardosa milvina. We show that subtle variation in the personality composition of P. milvina populations generate wildly different prey communities, where a mixture of both active and sedentary individuals performs best at suppressing prey abundance. Our results provide the first experimental evidence that predator personality types can generate contrasting prey communities. Moreover, our results suggest that manipulating the representation of predator personality types may be a profitable avenue by which one can maximize the biocontrol potential of predator populations.

Functional Ecology

1. Consistent behavioural differences between individuals have far-reaching implications for ecol... more 1. Consistent behavioural differences between individuals have far-reaching implications for ecology and evolution, including how populations cope with increasing anthropogenic changes, notably pesticides. Although sublethal doses of insecticides are known to alter behaviour, current studies on the relationship between toxicants and behaviour tend to ignore effects on individual variation.
2. Our objective was to determine whether sublethal exposure to an organophosphate insecticide could affect the consistency of individual behaviour and disrupt behavioural correlations, in a jumping spider occurring in agroecosystems. Adults of the jumping spider Eris militaris (Araneae: Salticidae) were scored by an open-field and a prey-capture assay, each conducted as pre- and post-insecticidal exposure to the organophosphate phosmet. Half of the individuals received no exposure to the insecticide to provide a control group. We then estimated the changes in repeatability, a measure of the extent of personality differences, and in behavioural correlations between control and insecticide-treated groups.
3. Although insecticide exposure had no discernable effects on the population’s average behaviours, insecticide-exposed individuals showed an average of 23 % lower repeatability and the correlation between activity and prey capture was more strongly collapsed in females.
4. Our results provide clear evidence that exposure to sublethal doses of insecticides on an important arthropod predator in agroecosystems causes substantial alteration of personality differences even in absence of a population-wide shift in behaviour. This suggests insecticide effects are more complex than previously thought and indicates high variation in the way individuals coped with insecticidal exposure.
5. By altering the consistency of behavioural traits and their correlations, exposure to sublethal concentrations of insecticides can have subtle effects on behavioural expression, which may ultimately affect biocontrol performance in an important arthropod predator in agroecosystems. Our study calls for an increasing focus on individual behavioural variation when testing the effects of pesticides on non-targeted fauna.

Animal Behaviour

Consistent behavioural differences between individuals have far-reaching implications for ecology... more Consistent behavioural differences between individuals have far-reaching implications for ecology and evolution. Determining the mechanisms maintaining them is a central focus of behavioural ecology. Anthropogenic contaminants are rarely considered for their contribution to such behavioural differences. Yet, anthropogenic contaminants and behaviour interact through their respective effects on resource acquisition and the pattern of resource allocation to growth, reproduction and survival. Such interactions between behaviour and anthropogenic contaminants could either increase and maintain or erode consistent behavioural variation in animal populations. We propose a general framework integrating the relationships linking individual differences in behaviour, exposure to and accumulation of anthropogenic contaminants, and resource acquisition/allocation patterns. We discuss the type of approach required, the type of data missing in the current literature, and two study systems where insights could be gained by investigating the relationships between individual behavioural variation and anthropogenic contaminants. We hope to stimulate cross-fertilization between behavioural ecology and ecotoxicology and show how a mechanistic approach based on repeated measurements can contribute to this area of research.

Ethology

Variations in environmental conditions can influence behavioral syndromes (correlated tendencies ... more Variations in environmental conditions can influence behavioral syndromes (correlated tendencies in behaviors), and understanding the factors that shape trait covariation is particularly relevant when species are challenged by environmental changes. We investigated how behav- ioral syndromes varied at extremes of a gradient of anthropogenic distur- bance, using apple orchards with different histories of insecticidal applications as a model system. Eris militaris (Araneae: Salticidae) jumping spiders were sampled from an insecticide-free orchard and an insecticide- treated orchard from Southern Quﰀebec. Spiders were tested for activity, aggression, boldness, and voracity under standardized conditions. Behav- ioral syndrome structure was compared between the two populations using Bayesian multiresponse models and structural equation modeling. Syndrome structure differed significantly between the two populations. The insecticide-free population showed evidence of a syndrome involving all measured traits, while only aggression, boldness and voracity were cor- related in the insecticide-treated population. The insecticide-free popula- tion showed negative correlations between active and voracious behavioral types vs. aggressive and bold types while the insecticide-trea- ted population showed a negative correlation between aggression-bold- ness and voracity. This research is a first step in investigating the impact anthropogenic disturbances on behavioral syndromes and demonstrates that behavioral syndromes vary with respect to insecticidal applications.

Journal of Arachnology, Jan 1, 2012

Spiders are important generalist predators in agroecosystems, yet early season colonization is po... more Spiders are important generalist predators in agroecosystems, yet early season colonization is poorly understood, especially in northern regions. We investigated colonization patterns of spiders in agricultural fields after snow-melt in four cornfields in southwestern Quebec (Canada). Paired pitfall traps were associated with two drift fences to obtain data about immigration to and emigration from the fields and were placed at increasing distances from a deciduous forest border. Control traps were placed four meters inside the forest. Seventy-four species were collected, dominated by Linyphiidae and Lycosidae. Most of the fauna was already active during the first weeks of collection, and early season assemblages differed from late season assemblages. A significant ecotone effect was found for spider abundance, species richness and species composition. This study stresses the importance of early season spider activity in agroecosystems, and this context is relevant to a period of colonization by the dominant, active spider species.

Despite recent progress in elucidating the genetic basis for behavioral variation, the effects of... more Despite recent progress in elucidating the genetic basis for behavioral variation, the effects of the developmental environment on the maintenance and generation of behavioral variation across multiple traits remain poorly resolved. We investigated how nutritional status during development affected behavioral variation and covariance between activity in an open field test and response to cues of predator presence in the house cricket (Acheta domesticus). We provided 98 juvenile crickets with either a high or low quality diet during development, throughout which we measured body mass, activity in a modified open-field, and response to predator excreta twice every week for 3 weeks. Diet quality affected growth rate but not average activity or response to cues of predator presence, nor the correlation between the 2. However, repeatability (τ) in response to cues of predator presence was reduced by 0.24 in individuals exposed to the high quality diet versus the low quality diet. Larger individuals also increased their response to predator cues when reared on a high quality diet, suggesting negative feedbacks between growth rate and antipredator behaviors. Our results also indicate that changes in the developmental environment are not sufficient to collapse behavioral syndromes, suggesting a genetic link between activity and predator cue response in house crickets, and that nutritional stress early in life can lead to more consistent behavioral responses when individuals faced predatory threats. Our results demonstrate that subtle differences in the quality of the environment experienced early in life can influence how individuals negotiate behavioral and life-history trade-offs later in life.

The pace-of-life hypothesis predicts that among-individual differences in behaviour should integr... more The pace-of-life hypothesis predicts that among-individual differences in behaviour should integrate with a wide variety of morphological, metabolic and life-history traits along a slow to fast pace-of-life continuum. Support for the pace-of-life hypothesis has been mixed, in part because most empirical tests have been conducted strictly at the phenotypic level and have thus conflated genetic and environmental sources of covariance among traits. In the present study, we tested the hypothesis that, ac- cording to the predictions of the pace-of-life hypothesis, body mass, routine metabolic rate, activity and exploratory propensity are positively integrated in the house cricket Acheta domesticus (Orthoptera: Gryllidae). Using modified open field behavioural tests and flow-through respirometry, we determined whether among-individual differences are correlated across morphology, behaviour and metabolism in 50 male house crickets. All traits were repeatable, but we found poor evidence for overall integration across traits. Instead we found evidence for modularity, with behavioural traits covarying independently from mass and routine metabolic rate. Modularity, like that found here between activity and exploratory propensity, has been suggested to facilitate adaptive evolutionary change by coupling functionally related traits into suites on which selection can act more rapidly.

Most taxa show consistent individual differences in behavior, a phenomenon often referred to as a... more Most taxa show consistent individual differences in behavior, a phenomenon often referred to as animal "personalities". While the links between individual personality and fitness have received considerable attention, little information is available on how animal personality impacts higher order ecological processes, such as community dynamics. Using a mesocosm experiment, we subjected a representative community of alfalfa pests to different compositions of personality types of the wolf spider Pardosa milvina. We show that subtle variation in the personality composition of P. milvina populations generate wildly different prey communities, where a mixture of both active and sedentary individuals performs best at suppressing prey abundance. Our results provide the first experimental evidence that predator personality types can generate contrasting prey communities. Moreover, our results suggest that manipulating the representation of predator personality types may be a profitable avenue by which one can maximize the biocontrol potential of predator populations.

Functional Ecology

1. Consistent behavioural differences between individuals have far-reaching implications for ecol... more 1. Consistent behavioural differences between individuals have far-reaching implications for ecology and evolution, including how populations cope with increasing anthropogenic changes, notably pesticides. Although sublethal doses of insecticides are known to alter behaviour, current studies on the relationship between toxicants and behaviour tend to ignore effects on individual variation.
2. Our objective was to determine whether sublethal exposure to an organophosphate insecticide could affect the consistency of individual behaviour and disrupt behavioural correlations, in a jumping spider occurring in agroecosystems. Adults of the jumping spider Eris militaris (Araneae: Salticidae) were scored by an open-field and a prey-capture assay, each conducted as pre- and post-insecticidal exposure to the organophosphate phosmet. Half of the individuals received no exposure to the insecticide to provide a control group. We then estimated the changes in repeatability, a measure of the extent of personality differences, and in behavioural correlations between control and insecticide-treated groups.
3. Although insecticide exposure had no discernable effects on the population’s average behaviours, insecticide-exposed individuals showed an average of 23 % lower repeatability and the correlation between activity and prey capture was more strongly collapsed in females.
4. Our results provide clear evidence that exposure to sublethal doses of insecticides on an important arthropod predator in agroecosystems causes substantial alteration of personality differences even in absence of a population-wide shift in behaviour. This suggests insecticide effects are more complex than previously thought and indicates high variation in the way individuals coped with insecticidal exposure.
5. By altering the consistency of behavioural traits and their correlations, exposure to sublethal concentrations of insecticides can have subtle effects on behavioural expression, which may ultimately affect biocontrol performance in an important arthropod predator in agroecosystems. Our study calls for an increasing focus on individual behavioural variation when testing the effects of pesticides on non-targeted fauna.

Animal Behaviour

Consistent behavioural differences between individuals have far-reaching implications for ecology... more Consistent behavioural differences between individuals have far-reaching implications for ecology and evolution. Determining the mechanisms maintaining them is a central focus of behavioural ecology. Anthropogenic contaminants are rarely considered for their contribution to such behavioural differences. Yet, anthropogenic contaminants and behaviour interact through their respective effects on resource acquisition and the pattern of resource allocation to growth, reproduction and survival. Such interactions between behaviour and anthropogenic contaminants could either increase and maintain or erode consistent behavioural variation in animal populations. We propose a general framework integrating the relationships linking individual differences in behaviour, exposure to and accumulation of anthropogenic contaminants, and resource acquisition/allocation patterns. We discuss the type of approach required, the type of data missing in the current literature, and two study systems where insights could be gained by investigating the relationships between individual behavioural variation and anthropogenic contaminants. We hope to stimulate cross-fertilization between behavioural ecology and ecotoxicology and show how a mechanistic approach based on repeated measurements can contribute to this area of research.

Ethology

Variations in environmental conditions can influence behavioral syndromes (correlated tendencies ... more Variations in environmental conditions can influence behavioral syndromes (correlated tendencies in behaviors), and understanding the factors that shape trait covariation is particularly relevant when species are challenged by environmental changes. We investigated how behav- ioral syndromes varied at extremes of a gradient of anthropogenic distur- bance, using apple orchards with different histories of insecticidal applications as a model system. Eris militaris (Araneae: Salticidae) jumping spiders were sampled from an insecticide-free orchard and an insecticide- treated orchard from Southern Quﰀebec. Spiders were tested for activity, aggression, boldness, and voracity under standardized conditions. Behav- ioral syndrome structure was compared between the two populations using Bayesian multiresponse models and structural equation modeling. Syndrome structure differed significantly between the two populations. The insecticide-free population showed evidence of a syndrome involving all measured traits, while only aggression, boldness and voracity were cor- related in the insecticide-treated population. The insecticide-free popula- tion showed negative correlations between active and voracious behavioral types vs. aggressive and bold types while the insecticide-trea- ted population showed a negative correlation between aggression-bold- ness and voracity. This research is a first step in investigating the impact anthropogenic disturbances on behavioral syndromes and demonstrates that behavioral syndromes vary with respect to insecticidal applications.

Journal of Arachnology, Jan 1, 2012

Spiders are important generalist predators in agroecosystems, yet early season colonization is po... more Spiders are important generalist predators in agroecosystems, yet early season colonization is poorly understood, especially in northern regions. We investigated colonization patterns of spiders in agricultural fields after snow-melt in four cornfields in southwestern Quebec (Canada). Paired pitfall traps were associated with two drift fences to obtain data about immigration to and emigration from the fields and were placed at increasing distances from a deciduous forest border. Control traps were placed four meters inside the forest. Seventy-four species were collected, dominated by Linyphiidae and Lycosidae. Most of the fauna was already active during the first weeks of collection, and early season assemblages differed from late season assemblages. A significant ecotone effect was found for spider abundance, species richness and species composition. This study stresses the importance of early season spider activity in agroecosystems, and this context is relevant to a period of colonization by the dominant, active spider species.