Early environments can profoundly influence an organism in ways that persist over its life. In re... more Early environments can profoundly influence an organism in ways that persist over its life. In reptiles, early thermal environments (nest temperatures) can impact offspring phenotype and survival in important ways, yet we still lack an understanding of whether general trends exist and the magnitude of impact. Understanding these patterns is important in predicting how climate change will affect reptile populations and the role of phenotypic plasticity in buffering populations. We compiled data from 175 reptile studies to examine, and quantify, the effect of incubation temperature on phenotype and survival. Using meta-analytic approaches (standardized mean difference between incubation treatments, Hedges' g), we show that across all trait types examined there is, on average, a moderate to large magnitude of effect of incubation temperatures (absolute effect: |g| = 0.75). Unsurprisingly, this influence was extremely large for incubation duration, as predicted, with warmer temperatures decreasing incubation time overall (g = −8.42). Other trait types, including behaviour, physiology, morphology, performance, and survival experienced reduced, but still mostly moderate to large effects, with particularly strong effects on survival. Moreover, the impact of incubation temperature persisted at least one-year post-hatching, suggesting that these effects have the potential to impact fitness in the long term. The magnitude of effect increased as the change in temperature increased (e.g. 6 • C versus 2 • C) in almost all cases, and tended to decrease when temperatures of the treatments fluctuated around a mean temperature compared to when they were constant. The effect also depended on the mid-temperature of the comparison, but not in consistent ways, with some traits experiencing the greatest effects at extreme temperatures, while others did not. The highly heterogeneous nature of the effects we observe, along with a large amount of unexplained variability, indicates that the shape of reaction norms between phenotype and temperature, along with ecological and/or experimental factors, are important when considering general patterns. Our analyses provide new insights into the effects of incubation environments on reptile phenotype and survival and allow general, albeit coarse, predictions for taxa experiencing warming nest temperatures under climatic change.
Early social environment can play a significant role in shaping behavioural development. For inst... more Early social environment can play a significant role in shaping behavioural development. For instance, in many social mammals and birds, isolation rearing results in individuals that are less exploratory, shyer, less social and more aggressive than individuals raised in groups. Moreover, dynamic aspects of social environments, such as the nature of relationships between individuals, can also impact the trajectory of development. We tested if being raised alone or socially affects behavioural development in the family-living tree skink, Egernia striolata. Juveniles were raised in two treatments: alone or in a pair. We assayed exploration, boldness, sociability and aggression repeatedly throughout each juvenile’s first year of life, and also assessed social interactions between pairs to determine if juveniles formed dominant–subordinate relationships. We found that male and/or the larger skinks within social pairs were dominant. Developing within this social environment reduced skink growth, and subordinate skinks were more prone to tail loss. Thus, living with a conspecific was costly for E. striolata. The predicted negative effects of isolation failed to materialize. Nevertheless, there were significant differences in behavioural traits depending on the social environment (isolated, dominant or subordinate member of a pair). Isolated skinks were more social than subordinate skinks. Subordinate skinks also became more aggressive over time, whereas isolated and dominant skinks showed invariable aggression. Dominant skinks became bolder over time, whereas isolated and subordinate skinks were relatively stable in their boldness. In summary, our study is evidence that isolation rearing does not consistently affect behaviour across all social taxa. Our study also demonstrates that the social environment plays an important role in behavioural development of a family-living lizard.
Meta-analysis is a statistical procedure for analyzing the combined data from different studies, ... more Meta-analysis is a statistical procedure for analyzing the combined data from different studies, and can be a major source of concise up-to-date information. The overall conclusions of a meta-analysis, however, depend heavily on the quality of the meta-analytic process, and an appropriate evaluation of the quality of meta-analysis (meta-evaluation) can be challenging. We outline ten questions biologists can ask to critically appraise a meta-analysis. These questions could also act as simple and accessible guidelines for the authors of meta-analyses. We focus on meta-analyses using non-human species, which we term 'biological' meta-analysis. Our ten questions are aimed at enabling a biologist to evaluate whether a biological meta-analysis embodies 'mega-enlightenment', a 'mega-mistake', or something in between.
Subject Areas: evolution, ecology, health and disease and epidemiology Nutritional environments, ... more Subject Areas: evolution, ecology, health and disease and epidemiology Nutritional environments, particularly those experienced during early life, are hypothesized to affect longevity. A recent cross-taxa meta-analysis found that, depending upon circumstance, average longevity may be increased or decreased by early-life dietary restriction. Unstudied are the effects of diet during development on among-individual variance in longevity. Here, we address this issue using emerging methods for meta-analysis of variance. We found that, in general , standard deviation (s.d.) in longevity is around 8% higher under early-life dietary restriction than a standard diet. The effects became especially profound when dietary insults were experienced prenatally (s.d. increased by 29%) and/ or extended into adulthood (s.d. increased by 36.6%). Early-life dietary restriction may generate variance in longevity as a result of increased variance in resource acquisition or allocation, but the mechanisms underlying these largely overlooked patterns clearly warrant elucidation.
Meta-analysis is an important tool for synthesizing research on a variety of topics in ecology an... more Meta-analysis is an important tool for synthesizing research on a variety of topics in ecology and evolution, including molecular ecology, but can be susceptible to non-independence. Non-independence can affect two major interrelated components of a meta-analysis: 1) the calculation of effect size statistics and 2) the estimation of overall meta-analytic estimates and their uncertainty. While some solutions to non-independence exist at the statistical analysis stages, there is little advice on what to do when complex analyses are not possible, or when studies with non-independent experimental designs exist in the data. Here we argue that exploring the effects of procedural decisions in a meta-analysis (e.g., inclusion of different quality data, choice of effect size) and statistical assumptions (e.g., assuming no phylogenetic covariance) using sensitivity analyses are extremely important in assessing the impact of non-independence. Sensitivity analyses can provide greater confidence...
Evidence of social learning, whereby the actions of an animal facilitate the acquisition of new i... more Evidence of social learning, whereby the actions of an animal facilitate the acquisition of new information by another, is taxonomically biased towards mammals, especially primates, and birds. However, social learning need not be limited to group-living animals because species with less interaction can still benefit from learning about potential predators, food sources, rivals and mates. We trained male skinks (Eulamprus quoyii), a mostly solitary lizard from eastern Australia, in a two-step foraging task. Lizards belonging to 'young' and 'old' age classes were presented with a novel instrumental task (displacing a lid) and an association task (reward under blue lid). We did not find evidence for age-dependent learning of the instrumental task; however, young males in the presence of a demonstrator learnt the association task faster than young males without a demonstrator, whereas old males in both treatments had similar success rates. We present the first evidence o...
To persist, unisexual and asexual eukaryotes must have reproductive modes that circumvent normal ... more To persist, unisexual and asexual eukaryotes must have reproductive modes that circumvent normal bisexual reproduction. Parthenogenesis, gynogenesis, and hybridogenesis are the modes that have generally been ascribed to various unisexuals. Unisexual Ambystoma are abundant around the Great Lakes region of North America, and have variously been described as having all 3 reproductive modes. Diploid and polyploid unisexuals have nuclear genomes that combine the haploid genomes of 2 to 4 distinct sexual species, but the mtDNA is unlike any of those 4 species and is similar to another species, Ambystoma barbouri. To obtain better resolution of the reproductive mode used by unisexual Ambystoma and to explore the relationship of A. barbouri to the unisexuals, we sequenced the mitochondrial control and highly variable intergenic spacer region of 48 ambystomatids, which included 28 unisexuals, representatives of the 4 sexual species and A. barbouri. The unisexuals have similar sequences over most of their range, and form a close sister group to A. barbouri, with an estimated time of divergence of 2.4-3.9 million years ago. Individuals from the Lake Erie Islands (Kelleys, Pelee, North Bass) have a haplotype that demonstrates an isolation event. We examined highly variable microsatellite loci, and found that the genetic makeup of the unisexuals is highly variable and that unisexual individuals share microsatellite alleles with sexual individuals within populations. Although many progeny from the same female had the same genotype for 5 microsatellite DNA loci, there was no indication that any particular genome is consistently inherited in a clonal fashion in a population. The reproductive mode used by unisexual Ambystoma appears to be unique; we suggest kleptogenesis as a new unisexual reproductive mode that is used by these salamanders.
Early environments can profoundly influence an organism in ways that persist over its life. In re... more Early environments can profoundly influence an organism in ways that persist over its life. In reptiles, early thermal environments (nest temperatures) can impact offspring phenotype and survival in important ways, yet we still lack an understanding of whether general trends exist and the magnitude of impact. Understanding these patterns is important in predicting how climate change will affect reptile populations and the role of phenotypic plasticity in buffering populations. We compiled data from 175 reptile studies to examine, and quantify, the effect of incubation temperature on phenotype and survival. Using meta-analytic approaches (standardized mean difference between incubation treatments, Hedges' g), we show that across all trait types examined there is, on average, a moderate to large magnitude of effect of incubation temperatures (absolute effect: |g| = 0.75). Unsurprisingly, this influence was extremely large for incubation duration, as predicted, with warmer temperatures decreasing incubation time overall (g = −8.42). Other trait types, including behaviour, physiology, morphology, performance, and survival experienced reduced, but still mostly moderate to large effects, with particularly strong effects on survival. Moreover, the impact of incubation temperature persisted at least one-year post-hatching, suggesting that these effects have the potential to impact fitness in the long term. The magnitude of effect increased as the change in temperature increased (e.g. 6 • C versus 2 • C) in almost all cases, and tended to decrease when temperatures of the treatments fluctuated around a mean temperature compared to when they were constant. The effect also depended on the mid-temperature of the comparison, but not in consistent ways, with some traits experiencing the greatest effects at extreme temperatures, while others did not. The highly heterogeneous nature of the effects we observe, along with a large amount of unexplained variability, indicates that the shape of reaction norms between phenotype and temperature, along with ecological and/or experimental factors, are important when considering general patterns. Our analyses provide new insights into the effects of incubation environments on reptile phenotype and survival and allow general, albeit coarse, predictions for taxa experiencing warming nest temperatures under climatic change.
Early social environment can play a significant role in shaping behavioural development. For inst... more Early social environment can play a significant role in shaping behavioural development. For instance, in many social mammals and birds, isolation rearing results in individuals that are less exploratory, shyer, less social and more aggressive than individuals raised in groups. Moreover, dynamic aspects of social environments, such as the nature of relationships between individuals, can also impact the trajectory of development. We tested if being raised alone or socially affects behavioural development in the family-living tree skink, Egernia striolata. Juveniles were raised in two treatments: alone or in a pair. We assayed exploration, boldness, sociability and aggression repeatedly throughout each juvenile’s first year of life, and also assessed social interactions between pairs to determine if juveniles formed dominant–subordinate relationships. We found that male and/or the larger skinks within social pairs were dominant. Developing within this social environment reduced skink growth, and subordinate skinks were more prone to tail loss. Thus, living with a conspecific was costly for E. striolata. The predicted negative effects of isolation failed to materialize. Nevertheless, there were significant differences in behavioural traits depending on the social environment (isolated, dominant or subordinate member of a pair). Isolated skinks were more social than subordinate skinks. Subordinate skinks also became more aggressive over time, whereas isolated and dominant skinks showed invariable aggression. Dominant skinks became bolder over time, whereas isolated and subordinate skinks were relatively stable in their boldness. In summary, our study is evidence that isolation rearing does not consistently affect behaviour across all social taxa. Our study also demonstrates that the social environment plays an important role in behavioural development of a family-living lizard.
Meta-analysis is a statistical procedure for analyzing the combined data from different studies, ... more Meta-analysis is a statistical procedure for analyzing the combined data from different studies, and can be a major source of concise up-to-date information. The overall conclusions of a meta-analysis, however, depend heavily on the quality of the meta-analytic process, and an appropriate evaluation of the quality of meta-analysis (meta-evaluation) can be challenging. We outline ten questions biologists can ask to critically appraise a meta-analysis. These questions could also act as simple and accessible guidelines for the authors of meta-analyses. We focus on meta-analyses using non-human species, which we term 'biological' meta-analysis. Our ten questions are aimed at enabling a biologist to evaluate whether a biological meta-analysis embodies 'mega-enlightenment', a 'mega-mistake', or something in between.
Subject Areas: evolution, ecology, health and disease and epidemiology Nutritional environments, ... more Subject Areas: evolution, ecology, health and disease and epidemiology Nutritional environments, particularly those experienced during early life, are hypothesized to affect longevity. A recent cross-taxa meta-analysis found that, depending upon circumstance, average longevity may be increased or decreased by early-life dietary restriction. Unstudied are the effects of diet during development on among-individual variance in longevity. Here, we address this issue using emerging methods for meta-analysis of variance. We found that, in general , standard deviation (s.d.) in longevity is around 8% higher under early-life dietary restriction than a standard diet. The effects became especially profound when dietary insults were experienced prenatally (s.d. increased by 29%) and/ or extended into adulthood (s.d. increased by 36.6%). Early-life dietary restriction may generate variance in longevity as a result of increased variance in resource acquisition or allocation, but the mechanisms underlying these largely overlooked patterns clearly warrant elucidation.
Meta-analysis is an important tool for synthesizing research on a variety of topics in ecology an... more Meta-analysis is an important tool for synthesizing research on a variety of topics in ecology and evolution, including molecular ecology, but can be susceptible to non-independence. Non-independence can affect two major interrelated components of a meta-analysis: 1) the calculation of effect size statistics and 2) the estimation of overall meta-analytic estimates and their uncertainty. While some solutions to non-independence exist at the statistical analysis stages, there is little advice on what to do when complex analyses are not possible, or when studies with non-independent experimental designs exist in the data. Here we argue that exploring the effects of procedural decisions in a meta-analysis (e.g., inclusion of different quality data, choice of effect size) and statistical assumptions (e.g., assuming no phylogenetic covariance) using sensitivity analyses are extremely important in assessing the impact of non-independence. Sensitivity analyses can provide greater confidence...
Evidence of social learning, whereby the actions of an animal facilitate the acquisition of new i... more Evidence of social learning, whereby the actions of an animal facilitate the acquisition of new information by another, is taxonomically biased towards mammals, especially primates, and birds. However, social learning need not be limited to group-living animals because species with less interaction can still benefit from learning about potential predators, food sources, rivals and mates. We trained male skinks (Eulamprus quoyii), a mostly solitary lizard from eastern Australia, in a two-step foraging task. Lizards belonging to 'young' and 'old' age classes were presented with a novel instrumental task (displacing a lid) and an association task (reward under blue lid). We did not find evidence for age-dependent learning of the instrumental task; however, young males in the presence of a demonstrator learnt the association task faster than young males without a demonstrator, whereas old males in both treatments had similar success rates. We present the first evidence o...
To persist, unisexual and asexual eukaryotes must have reproductive modes that circumvent normal ... more To persist, unisexual and asexual eukaryotes must have reproductive modes that circumvent normal bisexual reproduction. Parthenogenesis, gynogenesis, and hybridogenesis are the modes that have generally been ascribed to various unisexuals. Unisexual Ambystoma are abundant around the Great Lakes region of North America, and have variously been described as having all 3 reproductive modes. Diploid and polyploid unisexuals have nuclear genomes that combine the haploid genomes of 2 to 4 distinct sexual species, but the mtDNA is unlike any of those 4 species and is similar to another species, Ambystoma barbouri. To obtain better resolution of the reproductive mode used by unisexual Ambystoma and to explore the relationship of A. barbouri to the unisexuals, we sequenced the mitochondrial control and highly variable intergenic spacer region of 48 ambystomatids, which included 28 unisexuals, representatives of the 4 sexual species and A. barbouri. The unisexuals have similar sequences over most of their range, and form a close sister group to A. barbouri, with an estimated time of divergence of 2.4-3.9 million years ago. Individuals from the Lake Erie Islands (Kelleys, Pelee, North Bass) have a haplotype that demonstrates an isolation event. We examined highly variable microsatellite loci, and found that the genetic makeup of the unisexuals is highly variable and that unisexual individuals share microsatellite alleles with sexual individuals within populations. Although many progeny from the same female had the same genotype for 5 microsatellite DNA loci, there was no indication that any particular genome is consistently inherited in a clonal fashion in a population. The reproductive mode used by unisexual Ambystoma appears to be unique; we suggest kleptogenesis as a new unisexual reproductive mode that is used by these salamanders.
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