Individuality meets plasticity: Endocrine phenotypes across male dominance rank acquisition in guinea pigs living in a complex social environment

Mutwill, Alexandra M.; Schielzeth, Holger; Zimmermann, Tobias D.; Richter, S. Helene; Kaiser, Sylvia; Sachser, Norbert

doi:10.1016/j.yhbeh.2021.104967

Cited by 12 publications

(18 citation statements)

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“…We did not find evidence for a relationship between dominance rank index and cortisol concentrations in this population of female guinea pigs. This is in agreement with previous studies with male guinea pigs [ 29 , 37 ] which failed to detect a correlation between dominance rank and cortisol levels. The females used in the present study were housed with these groupmates for several months prior to the beginning of the study, and indeed we found that rank index was repeatable.…”

Section: Discussionsupporting

confidence: 94%

“…Cortisol responsiveness was significantly repeatable at both sampling times (1 and 2 h after being placed in a novel environment), but baseline cortisol was not repeatable. Despite the low sample size of the current study (N = 12 individuals), this result is consistent with recent meta-analyses [ 28 , 30 , 31 ] as well as current research with male guinea pigs [ 29 , 37 ] that consistently find cortisol responsiveness to be more repeatable than baseline cortisol. Repeatability is calculated as the proportion of total phenotypic variance that is attributed to the between-individual component, and decomposing variance into the within- and between-individual components aids in understanding why measurements differ in repeatability [ 32 ].…”

Section: Discussionsupporting

confidence: 92%

“…This study aims to investigate whether dominance rank, baseline cortisol level, and cortisol responsiveness (here defined as the absolute cortisol concentration after 1 and 2 h of exposure to a stressor) [ 29 , 33 , 34 ] are repeatable and whether dominance rank correlates to cortisol concentrations in female guinea pigs ( Cavia aperea f. porcellus ). Guinea pigs are social mammals, and females form linear dominance hierarchies [ 12 ].…”

Section: Introductionmentioning

confidence: 99%

“…Female dominance hierarchies in wild and captive groups of wild cavies ( Cavia aperea ) follow an age-graded structure [ 35 ], with young females integrating into a female group associated with a nearby male [ 36 ]. It has been previously shown that dominance rank (Pearson's r = 0.527, [ 37 ]) and cortisol responsiveness (after 1 h: Pearson's r = 0.686 [ 37 ]; after 2 h: Pearson's r = 0.797 [ 37 ], R = 0.427 [ 29 ]) are stable in male guinea pigs, and that the social environment can have a profound impact on the endocrine profile of males [ 18 , 33 , 38 ]. However, it is not known whether cortisol concentrations are repeatable and associated with dominance rank in female guinea pigs.…”

Section: Introductionmentioning

confidence: 99%

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Repeatability of endocrine traits and dominance rank in female guinea pigs

et al. 2022

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Background Glucocorticoids (e.g. cortisol) are associated with variation in social behavior, and previous studies have linked baseline as well as challenge-induced glucocorticoid concentrations to dominance status. It is known that cortisol response to an acute challenge is repeatable and correlates to social behavior in males of many mammal species. However, it is unclear whether these patterns are also consistent for females. The aim of this study was to investigate whether baseline and response cortisol concentrations are repeatable in female guinea pigs (Cavia aperea f. porcellus) and whether dominance rank is stable and correlated to baseline cortisol concentration and/or cortisol responsiveness. Results Our results show that cortisol responsiveness (after 1 h: R = 0.635, 95% CI = 0.229, 0.927; after 2 h: R = 0.764, 95% CI = 0.433, 0.951) and dominance rank (R = 0.709, 95% CI = 0.316, 0.935) of females were significantly repeatable after six weeks but not correlated. Baseline cortisol was not repeatable (R = 0, 95% CI = 0, 0.690) and also did not correlate to dominance rank. Furthermore, the difference in repeatability estimates of baseline and response values was due to high within-individual variance of baseline cortisol concentration; the amount of between-individual variance was similar for baseline cortisol and the two measures of cortisol responsiveness. Conclusions Females occupying different dominance ranks did not have long-term differences in cortisol concentrations, and cortisol responsiveness does not seem to be significantly involved in the maintenance of dominance rank. Overall, this study reveals the remarkable stability of cortisol responsiveness and dominance rank in a female rodent, and it remains an open question whether the magnitude of cortisol responsiveness is adaptive in social contexts for females.

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Section: Discussionsupporting

confidence: 94%

Section: Discussionsupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Repeatability of endocrine traits and dominance rank in female guinea pigs

et al. 2022

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“…We analyze log-transformed testosterone titers and fit male identity as a random effect. As covariates the dataset contains the time point of measurement and a rank index derived from behavioral observations around the time of measurement ( Mutwill et al, 2021 ).…”

Section: Other Implementations In R Packagesmentioning

confidence: 99%

`partR2`: partitioning R²in generalized linear mixed models

Stoffel

Nakagawa

Schielzeth

2021

PeerJ

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183

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The coefficient of determination R2 quantifies the amount of variance explained by regression coefficients in a linear model. It can be seen as the fixed-effects complement to the repeatability R (intra-class correlation) for the variance explained by random effects and thus as a tool for variance decomposition. The R2 of a model can be further partitioned into the variance explained by a particular predictor or a combination of predictors using semi-partial (part) R2 and structure coefficients, but this is rarely done due to a lack of software implementing these statistics. Here, we introduce partR2, an R package that quantifies part R2 for fixed effect predictors based on (generalized) linear mixed-effect model fits. The package iteratively removes predictors of interest from the model and monitors the change in the variance of the linear predictor. The difference to the full model gives a measure of the amount of variance explained uniquely by a particular predictor or a set of predictors. partR2 also estimates structure coefficients as the correlation between a predictor and fitted values, which provide an estimate of the total contribution of a fixed effect to the overall prediction, independent of other predictors. Structure coefficients can be converted to the total variance explained by a predictor, here called ‘inclusive’ R2, as the square of the structure coefficients times total R2. Furthermore, the package reports beta weights (standardized regression coefficients). Finally, partR2 implements parametric bootstrapping to quantify confidence intervals for each estimate. We illustrate the use of partR2 with real example datasets for Gaussian and binomial GLMMs and discuss interactions, which pose a specific challenge for partitioning the explained variance among predictors.

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Low heritability and high phenotypic plasticity of salivary cortisol in response to environmental heterogeneity in a wild pinniped

Nagel

Kaiser

Stainfield

et al. 2022

Ecology and Evolution

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Individuals are unique in how they interact with and respond to their environment. Correspondingly, unpredictable challenges or environmental stressors often produce an individualized response of the hypothalamic‐pituitary‐adrenal (HPA) axis and its downstream effector cortisol. We used a fully crossed, repeated measures design to investigate the factors shaping individual variation in baseline cortisol in Antarctic fur seal pups and their mothers. Saliva samples were collected from focal individuals at two breeding colonies, one with low and the other with high density, during two consecutive years of contrasting food availability. Mothers and pups were sampled concurrently at birth and shortly before weaning, while pups were additionally sampled every 20 days. We found that heritability was low for baseline cortisol, while within‐individual repeatability and among‐individual variability were high. A substantial proportion of the variation in baseline cortisol could be explained in pups and mothers by a combination of intrinsic and extrinsic factors including sex, weight, day, season, and colony of birth. Our findings provide detailed insights into the individualization of endocrine phenotypes and their genetic and environmental drivers in a wild pinniped. Furthermore, the strong associations between cortisol and life history traits that we report in fur seals could have important implications for understanding the population dynamics of species impacted by environmental change.

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Individuality meets plasticity: Endocrine phenotypes across male dominance rank acquisition in guinea pigs living in a complex social environment

Cited by 12 publications

References 70 publications

Repeatability of endocrine traits and dominance rank in female guinea pigs

Repeatability of endocrine traits and dominance rank in female guinea pigs

`partR2`: partitioning R²in generalized linear mixed models

Low heritability and high phenotypic plasticity of salivary cortisol in response to environmental heterogeneity in a wild pinniped

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Individuality meets plasticity: Endocrine phenotypes across male dominance rank acquisition in guinea pigs living in a complex social environment

Cited by 12 publications

References 70 publications

Repeatability of endocrine traits and dominance rank in female guinea pigs

Repeatability of endocrine traits and dominance rank in female guinea pigs

partR2: partitioning R2in generalized linear mixed models

Low heritability and high phenotypic plasticity of salivary cortisol in response to environmental heterogeneity in a wild pinniped

Contact Info

Product

Resources

About

`partR2`: partitioning R²in generalized linear mixed models