ORCID Profile
0000-0002-6008-2672
Current Organisation
Stockholm University
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Publisher: Wiley
Date: 05-09-2018
DOI: 10.1111/EVO.13585
Abstract: Interactions between genotypes and environments are central to evolutionary genetics, but such interactions are typically described, rather than predicted from theory. Recent Bayesian models of development generate specific predictions about genotypic differences in developmental plasticity (changes in the value of a given trait as a result of a given experience) based on genotypic differences in the value of the trait that is expressed by naïve subjects. We used these models to make a priori predictions about the effects of an aversive olfactory conditioning regime on the response of Drosophila melanogaster larvae to the odor of ethyl acetate. As predicted, across 116 genotypes initial trait values were related to plasticity. Genotypes most strongly attracted to the odor of ethyl acetate when naïve reduced their attraction scores more as a result of the aversive training regime than those less attracted to the same odor when naïve. Thus, as predicted, the variance across genotypes in attraction scores was higher before than after the shared experience. These results support predictions generated by Bayesian models of development and indicate that such models can be successfully used to investigate how variation across genotypes in information derived from ancestors combines with personal experience to differentially affect developmental plasticity in response to specific types of experience.
Publisher: California Digital Library (CDL)
Date: 07-10-2021
Publisher: California Digital Library (CDL)
Date: 14-12-2020
Publisher: The Royal Society
Date: 2020
Abstract: Predation is a near ubiquitous factor of nature and a powerful selective force on prey. Moreover, it has recently emerged as an important driver in the evolution of brain anatomy, though population comparisons show ambiguous results with considerable unexplained variation. Here, we test the reproducibility of reduced predation on evolutionary trajectories of brain evolution. We make use of an introduction experiment, whereby guppies ( Poecilia reticulata ) from a single high predation stream were introduced to four low predation streams. After 8–9 years of natural selection in the wild and two generations of common garden conditions in the laboratory, we quantified brain anatomy. Relative brain region sizes did not differ between populations. However, we found a general increase and striking variation in relative brain size of introduced populations, which varied from no change to a 12.5% increase in relative brain weight, relative to the ancestral high predation population. We interpret this as evidence for non-parallel evolution, which implies a weak or inconsistent association of relative brain size with fitness in low predation sites. The evolution of brain anatomy appears sensitive to unknown environmental factors, or contingent on either chance events or historical legacies of environmental change.
Publisher: Oxford University Press (OUP)
Date: 11-2019
Abstract: Quantifying in idual variation in labile physiological or behavioral traits often involves repeated measures through time, so as to test for consistency of in idual differences (often using repeatability, “R”) and/or in idual differences in trendlines over time. Another form of temporal change in behavior is temporal autocorrelation, which predicts observations taken closely together in time to be correlated, leading to nonrandom residuals about in idual temporal trendlines. Temporal autocorrelation may result from slowly changing internal states (e.g., hormone or energy levels), leading to slowly changing behavior. Autocorrelation is a well-known phenomenon, but has been largely neglected by those studying in idual variation in behavior. Here, we provide two worked ex les which show substantial temporal autocorrelation (r 0.4) is present in spontaneous activity rates of guppies (Poecilia reticulata) and house mice (Mus domesticus) in stable laboratory conditions, even after accounting for temporal plasticity of in iduals. Second, we show that ignoring autocorrelation does bias estimates of R and temporal reaction norm variances upwards, both in our worked ex les and in separate simulations. This bias occurs due to the misestimation of in idual-specific means and slopes. Given the increasing use of technologies that generate behavioral and physiological data at high s ling rates, we can now study among- and within-in idual changes in behavior in more detailed ways, including autocorrelation, which we discuss from biological and methodological perspectives and provide recommendations and annotated R code to help researchers implement these models on their data.
Publisher: Oxford University Press (OUP)
Date: 17-11-2020
Abstract: The study of behavioral syndromes aims to understand among-in idual correlations of behavior, yielding insights into the ecological factors and proximate constraints that shape behavior. In parallel, interest has been growing in behavioral plasticity, with results commonly showing that animals vary in their behavioral response to environmental change. These two phenomena are inextricably linked—behavioral syndromes describe cross-trait or cross-context correlations, while variation in behavioral plasticity describes variation in response to changing context. However, they are often discussed separately, with plasticity analyses typically considering a single trait (univariate) across environments, while behavioral trait correlations are studied as multiple traits (multivariate) under one environmental context. Here, we argue that such separation represents a missed opportunity to integrate these concepts. Through observations of multiple traits while manipulating environmental conditions, we can quantify how the environment shapes behavioral correlations, thus quantifying how phenotypes are differentially constrained or integrated under different environmental conditions. Two analytical options exist which enable us to evaluate the context dependence of behavioral syndromes—multivariate reaction norms and character state models. These models are largely two sides of the same coin, but through careful interpretation we can use either to shift our focus to test how the contextual environment shapes trait covariances.
Publisher: Center for Open Science
Date: 31-10-2022
Abstract: Increased execution of replication studies contributes to the effort to restore credibility of empirical research. However, a second generation of problems arises: the number of potential replication targets is at a serious mismatch with available resources. Given limited resources, replication target selection should be well-justified, systematic, and transparently communicated. At present the discussion on what to consider when selecting a replication target is limited to theoretical discussion, self-reported justifications, and a few formalized suggestions. In this Registered Report, we proposed a study involving the scientific community to create a list of considerations for consultation when selecting a replication target in psychology. We employed a modified Delphi approach. First, we constructed a preliminary list of considerations. Second, we surveyed psychologists who previously selected a replication target with regards to their considerations. Third, we incorporated the results into the preliminary list of considerations and sent the updated list to a group of in iduals knowledgeable about concerns regarding replication target selection. Over the course of several rounds, we established consensus regarding what to consider when selecting a replication target.
Publisher: Springer Science and Business Media LLC
Date: 21-06-2022
DOI: 10.1007/S10682-022-10191-8
Abstract: Cognitive and sensory abilities are vital in affecting survival under predation risk, leading to selection on brain anatomy. However, how exactly predation and brain evolution are linked has not yet been resolved, as current empirical evidence is inconclusive. This may be due to predation pressure having different effects across life stages and/or due to confounding factors in ecological comparisons of predation pressure. Here, we used adult guppies ( Poecilia reticulata ) to experimentally test how direct predation during adulthood would impact the relative brain size and brain anatomy of surviving in iduals to examine if predators selectively remove in iduals with specific brain morphology. To this end, we compared fish surviving predation to control fish, which were exposed to visual and olfactory predator cues but could not be predated on. We found that predation impacted the relative size of female brains. However, this effect was dependent on body size, as larger female survivors showed relatively larger brains, while smaller survivors showed relatively smaller brains when compared to control females. We found no differences in male relative brain size between survivors and controls, nor for any specific relative brain region sizes for either sex. Our results corroborate the important, yet complex, role of predation as an important driver of variation in brain size.
Publisher: Wiley
Date: 03-05-2021
DOI: 10.1002/ECE3.7603
Abstract: Behavioral and physiological ecologists have long been interested in explaining the causes and consequences of trait variation, with a focus on in idual differences in mean values. However, the majority of phenotypic variation typically occurs within in iduals, rather than among in iduals (as indicated by average repeatability being less than 0.5). Recent studies have further shown that in iduals can also differ in the magnitude of variation that is unexplained by in idual variation or environmental factors (i.e., residual variation). The significance of residual variation, or why in iduals differ, is largely unexplained, but is important from evolutionary, methodological, and statistical perspectives. Here, we broadly reviewed literature on in idual variation in behavior and physiology, and located 39 datasets with sufficient repeated measures to evaluate in idual differences in residual variance. We then analyzed these datasets using methods that permit direct comparisons of parameters across studies. This revealed substantial and widespread in idual differences in residual variance. The magnitude of in idual variation appeared larger in behavioral traits than in physiological traits, and heterogeneity was greater in more controlled situations. We discuss potential ecological and evolutionary implications of in idual differences in residual variance and suggest productive future research directions.
Publisher: The Royal Society
Date: 09-08-2017
Abstract: Despite accumulating evidence for in idual variation in behavioural plasticity, there is currently little understanding of the causes and consequences of this variation. An outstanding question is whether in idual reaction norm (RN) slopes are consistent across different environmental variables—that is, whether an in idual that is highly responsive to one environmental variable will be equally responsive to a second variable. Another important and related question is whether RNs are themselves consistently expressed through time or whether they are simply state dependent. Here, we quantified in idual activity rates of zebrafish in response to independent manipulations of temperature and food availability that were repeated in discrete ‘bursts’ of s ling through time. In iduals that were thermally responsive were not more responsive to food deprivation, but they did exhibit greater unexplained variation. In idual RN slopes were consistent (repeatable) over time for both temperature ( R slope = 0.92) and food deprivation responses ( R slope = 0.4), as were mean activity rates in the standard environment ( R intercept = 0.83). Despite the high potential lability of behaviour, we have demonstrated consistency of behavioural RN components and identified potential energetic constraints leading to high consistency of thermal RNs and low consistency of food deprivation RNs.
Publisher: The Royal Society
Date: 10-2016
DOI: 10.1098/RSOS.160352
Abstract: There is a long-standing interest in behavioural ecology, exploring the causes and correlates of consistent in idual differences in mean behavioural traits (‘personality’) and the response to the environment (‘plasticity’). Recently, it has been observed that in iduals also consistently differ in their residual intrain idual variability (rIIV). This variation will probably have broad biological and methodological implications to the study of trait variation in labile traits, such as behaviour and physiology, though we currently need studies to quantify variation in rIIV, using more standardized and powerful methodology. Focusing on activity rates in guppies ( Poecilia reticulata ), we provide a model ex le, from s ling design to data analysis, in how to quantify rIIV in labile traits. Building on the doubly hierarchical generalized linear model recently used to quantify in idual differences in rIIV, we extend the model to evaluate the covariance between in idual mean values and their rIIV. After accounting for time-related change in behaviour, our guppies substantially differed in rIIV, and it was the active in iduals that tended to be more consistent (lower rIIV). We provide annotated data analysis code to implement these complex models, and discuss how to further generalize the model to evaluate covariances with other aspects of phenotypic variation.
Publisher: California Digital Library (CDL)
Date: 24-03-2021
Publisher: California Digital Library (CDL)
Date: 17-08-2020
No related grants have been discovered for David Mitchell.