Lifetime low behavioural plasticity of personality traits in the common vole (Microtus arvalis) under laboratory conditions

Individual differences in behaviour, referred to as animal personality, are consistent across time and contexts. Nevertheless, personality traits show behavioural plasticity, much like many other phenotypic traits. In the present study, we examined the relationship between personality traits and behavioural plasticity in the common vole (Microtus arvalis) under stable, long-lasting laboratory conditions. A total of 94 voles were tested in the classic open field test, designed to measure seven behavioural parameters (distance moved, grooming, immobility, rearing, running, scanning and walking duration) during a three-minute test. A total of 60 voles formed the experimental group and were tested at four different time points over their lifetime (1st, 3rd, 5th and 7th month); 34 voles formed the control group and were tested only once at the 7th month. All voles were of the same age. Based on principal component analysis (PCA), two ordination axes were determined: “exploration” and “activity.” For further analyses, “distance moved” and “scanning duration” were selected from the first axis and “walking duration” from the second. Using linear mixed-effect models (LMMs), we found highly significant random intercepts (i.e. personality traits) in all three behavioural parameters. However, evidence for behavioural plasticity was only found in the distance moved parameter, as determined from the random slope, and correlations between personality trait (intercept) and plasticity (slope) were not significant for any trait. During the experiment, variances of random effects were high and remained essentially the same, whilst the rank order of many individuals changed. Based on fixed effect slopes and a comparison with the control group, habituation was only significant for “walking duration.” The observed low behavioural plasticity could mirror stable (laboratory) conditions that result in the manifestation of original trait settings (genetic, early postnatal) or their gradual overcoming. These findings provide a starting point for further tests on free-living voles.     

Testing the prediction from sexual selection of a positive genetic correlation between human mate preferences and corresponding traits

Sexual selection can cause evolution in traits that affect mating success, and it has thus been implicated in the evolution of human physical and behavioural traits that influence attractiveness. We use a large sample of identical and nonidentical female twins to test the prediction from mate choice models that a trait under sexual selection will be positively genetically correlated with preference for that trait. Six of the eight preferences we investigated, i.e. height, hair colour, intelligence, creativity, exciting personality, and religiosity, exhibited significant positive genetic correlations with the corresponding traits, while the personality measures ‘easy going’ and ‘kind and understanding’ exhibited no phenotypic or genetic correlation between preference and trait. The positive results provide important evidence consistent with the involvement of sexual selection in the evolution of these human traits.     

Sex and the Syndrome: Individual and Population Consistency in Behaviour in Rock Pool Prawn Palaemon elegans

Animal personality has been widely documented across a range of species. The concept of personality is composed of individual behavioural consistency across time and between situations, and also behavioural trait correlations known as behavioural syndromes. Whilst many studies have now investigated the stability of individual personality traits, few have analysed the stability over time of entire behavioural syndromes. Here we present data from a behavioural study of rock pool prawns. We show that prawns are temporally consistent in a range of behaviours, including activity, exploration and boldness, and also that a behavioural syndrome is evident in this population. We find correlations between many behavioural traits (activity, boldness, shoaling and exploration). In addition, behavioural syndrome structure was consistent over time. Finally, few studies have explicitly studied the role of sex differences in personality traits, behavioural consistency and syndrome structure. We report behavioural differences between male and female prawns but no differences in patterns of consistency. Our study adds to the growing literature on animal personality, and provides evidence showing that syndromes themselves can exhibit temporal consistency.     

Heritability and genetic correlations of personality traits in a wild population of yellow‐bellied marmots (Marmota flaviventris)

Describing and quantifying animal personality is now an integral part of behavioural studies because individually distinctive behaviours have ecological and evolutionary consequences. Yet, to fully understand how personality traits may respond to selection, one must understand the underlying heritability and genetic correlations between traits. Previous studies have reported a moderate degree of heritability of personality traits, but few of these studies have either been conducted in the wild or estimated the genetic correlations between personality traits. Estimating the additive genetic variance and covariance in the wild is crucial to understand the evolutionary potential of behavioural traits. Enhanced environmental variation could reduce heritability and genetic correlations, thus leading to different evolutionary predictions. We estimated the additive genetic variance and covariance of docility in the trap, sociability (mirror image stimulation), and exploration and activity in two different contexts (open‐field and mirror image simulation experiments) in a wild population of yellow‐bellied marmots (Marmota flaviventris). We estimated both heritability of behaviours and of personality traits and found nonzero additive genetic variance in these traits. We also found nonzero maternal, permanent environment and year effects. Finally, we found four phenotypic correlations between traits, and one positive genetic correlation between activity in the open‐field test and sociability. We also found permanent environment correlations between activity in both tests and docility and exploration in the MIS test. This is one of a handful of studies to adopt a quantitative genetic approach to explain variation in personality traits in the wild and, thus, provides important insights into the potential variance available for selection.     

Population differences in behaviour are explained by shared within‐population trait correlations

Correlations in behavioural traits across time, situation and ecological context (i.e. ‘behavioural syndromes’ or ‘personality’) have been documented for a variety of behaviours, and in diverse taxa. Perhaps the most controversial inference from the behavioural syndromes literature is that correlated behaviour may act as an evolutionary constraint and evolutionary change in one’s behaviour may necessarily involve shifts in others. We test the two predictions of this hypothesis using comparative data from eighteen populations of the socially polymorphic spider, Anelosimus studiosus (Araneae, Theriidae). First, we ask whether geographically distant populations share a common syndrome. Second, we test whether population differences in behaviour are correlated similarly to within‐population trait correlations. Our results reveal that populations separated by as much as 36° latitude shared similar syndromes. Furthermore, population differences in behaviour were correlated in the same manner as within‐population trait correlations. That is, population divergence tended to be along the same axes as within‐population covariance. Together, these results suggest a lack of evolutionary independence in the syndrome’s constituent traits.     

SERUM LIPIDS IN NORMAL AND ABNORMAL SUBJECTS—Observations on Controlled Experiments

The relationship of diet to serum lipids and to atherosclerosis is a controversial subject. The data presented indicate that diets containing very large amounts of vegetable fat are consistently associated with a sharp fall in serum cholesterol and phospholipid, whereas administration of equal amounts of fat of animal origin is associated with a rise of the serum lipids to levels noted on an average mixed diet.In critical evaluation of elderly hospitalized diabetic patients with advanced atherosclerosis it was observed that there was close mathematical correlation between serum content of cholesterol, “lipoproteins,” and phospholipids. There was no obvious correlation between the degree or kind of atherosclerosis and any one of the lipid entities followed. Coronary occlusion occurred in a patient with one of the lowest levels of cholesterol and of lipoprotein.     

Premorbid personality and aggressive behavior in residents of psychogeriatic nursing homes

In the present study, the correlation was examined between pre-morbid personality traits and the occurrence of aggressive behaviour in residents of a psychogeriatric nursing home. The participants in the study were the close relatives of 39 residents of a psychogeriatric nursing home. These residents were selected on the basis of two subscales of the BOP assessment scale for elderly patients: Aggressive and annoying behaviour, and mental disability. Residents were divided into two groups: one group did not display aggressive behaviour, the other group displayed a great deal of such behaviour. The groups were comparable with regard to the degree of mental disability. To ascertain pre-morbid personality traits, use was made of the hetero-anamnestic personality questionnaire (HAP) and the Quick Big Five (QBF). We found no significant differences in any of the premorbid personality traits between the two groups. We could not confirm the conclusion of other authors that emotional lability (neuroticism) is a personality trait which makes people susceptible to developing aggressive behaviour. In conclusion, our study did not confirm the hypothesis that pre-morbid personality traits are useful to explain the occurrence of aggressive behaviour in residents of a psychogeriatric nursing home.     

Urine marking in male common voles: Does behavioural activity matter?

Rodent urine provides animals with a large amount of information, from the identity of the animal through its physical condition to social status. Many studies therefore focus on rodent urine-marking behaviour and use marking frequency as an indicator of social status or competitive ability. However, marking, like many other aspects of rodent behaviour, may be affected by individual behavioural activity, a factor that has not been examined so far. We therefore studied a relationship between male urine-marking in reaction to another male's marks (standard opponent) and individual personality profile, characterised by behavioural activity in an open field test (OFT). The marking appeared to be consistent and specific for particular individuals as there was a significant positive relationship between individual markings in two different phases of the experiment. The linkage between behavioural activity in the OFT and urine-marking frequency was non-linear (quadratic), which suggested that males with intermediate activity marked more intensively than males from the extremes of the behavioural spectra. The relationship between the opponent's and the tested males' markings was positive, however, we found no statistically significant evidence that the voles would attempt to overmark the opponent. Marking thus seems to have more of a self-advertising than a competitive function in the common vole. Further, as high marking activity is under strong intra- or intersexual selection, the result might suggest a stabilising selection of the personality trait described as behavioural activity in our study.     

Plasticity and evolution in correlated suites of traits

When organisms are faced with new or changing environments, a central challenge is the coordination of adaptive shifts in many different phenotypic traits. Relationships among traits may facilitate or constrain evolutionary responses to selection, depending on whether the direction of selection is aligned or opposed to the pattern of trait correlations. Attempts to predict evolutionary potential in correlated traits generally assume that correlations are stable across time and space; however, increasing evidence suggests that this may not be the case, and flexibility in trait correlations could bias evolutionary trajectories. We examined genetic and environmental influences on variation and covariation in a suite of behavioural traits to understand if and how flexibility in trait correlations influences adaptation to novel environments. We tested the role of genetic and environmental influences on behavioural trait correlations by comparing Trinidadian guppies (Poecilia reticulata) historically adapted to high‐ and low‐predation environments that were reared under native and non‐native environmental conditions. Both high‐ and low‐predation fish exhibited increased behavioural variance when reared under non‐native vs. native environmental conditions, and rearing in the non‐native environment shifted the major axis of variation among behaviours. Our findings emphasize that trait correlations observed in one population or environment may not predict correlations in another and that environmentally induced plasticity in correlations may bias evolutionary divergence in novel environments.     

High Total Cholesterol in Peripheral Blood Correlates with Poorer Hearing Recovery in Idiopathic Sudden Sensorineural Hearing Loss

Idiopathic sudden sensorineural hearing loss (ISSHL) is a common otologic emergency whose cause is still unclear. The importance of blood lipids in the pathogenesis of ISSHL is widely reported in literature. In fact elevated levels of low density lipoprotein cholesterol (LDL), total cholesterol (TC) and apolipoprotein B (Apo-B) have been proposed as risk factors for this pathology. No correlation has been described between serum lipid parameters and the prognosis of ISSHL. Aim of the present study was to identify prognostic factors associated with hearing recovery in a group of patients affected by ISSHL. Ninety-four patients with the diagnosis of ISSHL hospitalized between March 2013 and October 2014 were included in this study. Patients’ blood sampling and hearing assessments were carried out. Patients were divided into two groups as “recovered” and “unrecovered”, according to their response to the treatment. We found a statistically significant higher level of total cholesterol in the unrecovered group compared to the recovered one (p = 0.03). None of the other routine laboratory parameters have shown a statistically significant difference between the patients successfully treated and patients with poor outcomes. Total cholesterol concentrations may be a prognostic factor for recovery in ISSHL and should be assessed together with routine tests in patients with this condition. The other routine laboratory parameters seem to have no effect on the development and prognosis of this pathology.     

Environmental stress alters genetic regulation of novelty seeking in vervet monkeys

Considerable attention has been paid to identifying genetic influences and gene-environment interactions that increase vulnerability to environmental stressors, with promising but inconsistent results. A nonhuman primate model is presented here that allows assessment of genetic influences in response to a stressful life event for a behavioural trait with relevance for psychopathology. Genetic and environmental influences on free-choice novelty seeking behaviour were assessed in a pedigreed colony of vervet monkeys before and after relocation from a low stress to a higher stress environment. Heritability of novelty seeking scores, and genetic correlations within and between environments were conducted using variance components analysis. The results showed that novelty seeking was markedly inhibited in the higher stress environment, with effects persisting across a 2-year period for adults but not for juveniles. There were significant genetic contributions to novelty seeking scores in each year (h(2) = 0.35-0.43), with high genetic correlations within each environment (rhoG > 0.80) and a lower genetic correlation (rhoG = 0.35, non-significant) between environments. There were also significant genetic contributions to individual change scores from before to after the move (h(2) = 0.48). These results indicate that genetic regulation of novelty seeking was modified by the level of environmental stress, and they support a role for gene-environment interactions in a behavioural trait with relevance for mental health.     

刺槐叶片可塑生长的密度依赖性

为了探明刺槐叶片性状对种植密度的依赖性,通过刺槐田间栽培试验,研究了刺槐叶片可塑生长的密度依赖性以及主要叶片性状因子之间的关系.结果表明,不同种植密度条件下刺槐叶片厚度均无显著差异,但叶面积、叶绿素含蜃、叶片干重、比叶面积、叶干物质含量和叶片N含量差异显著,表明不同种植密度条件下刺槐叶性因子参数的变异较大,刺槐叶片性状对密度的依赖性较强.叶干重、叶厚度和叶片干物质含量均随种植密度的降低而呈增加趋势,叶片干物质含量与种植密度的相关性达到显著水平(P<0.01),而叶干重、叶厚度与种植密度的相关性不显著(P>0.05).比叶而积和叶片N含鼍均随种植密度的降低而降低,表明刺槐各叶性因子之间对种植密度的依赖性差异明显.对刺槐各叶性因子的相关分析表明,不同种植密度条件下各叶性因子之间的相关性及其强弱均存在差别,表明种植密度是影响刺槐叶性因子变异及叶性因子之间关系的因素之一.叶性特征对种植密度响应存在差异的主要原因是叶性因子之间的协同变化、刺槐生长微环境的差异和刺槐间竞争强度的差异,刺槐不同叶性因子之间的协调平衡和对种植密度响应程度与方向的差异表明了刺槐对其生长环境的适应.     

Natural variation in the molecular stress network correlates with a behavioural syndrome

In several species, individuals from the same population behave differently from each other. A functional link between variation in personality traits and the stress response has been suggested by studies in artificial selection lines in fish, birds and mammals. The aim of this study was to test whether the expression of genes involved in the stress response co-varies with personality traits in a natural population. Four personality traits, excreted cortisol level and brain expression of six candidate genes (CRF, CRF-R2, POMC1, GR1, GR2, MR) were measured in non-stressed wild-caught threespine sticklebacks (Gasterosteus aculeatus). We found correlations between variation in personality traits and variation in the expression of genes involved in the stress response. Aggressiveness was negatively correlated with cortisol levels. Boldness and aggressiveness formed a behavioural syndrome and were both positively correlated with brain expression of glucocorticoid receptors (GR1 and GR2). Boldness and exploration were positively correlated with expression of POMC1 but not with each other. Our results are compatible with a model that suggests that the aggressiveness-boldness behavioural syndrome could be the consequence of a physiological pleiotropic effect of glucocorticoid receptors, which are involved in the stress response and behaviour variation.     

Among‐population variation and correlations in sexually dimorphic traits of Silene latifolia

Abstract The degree of sexual dimorphism in a trait may be determined directly by disruptive selection, as well as by correlations with other traits under selection. We grew seeds from nine populations of the dioecious plant Silene latifolia in a common‐garden experiment to determine whether phenotypic variation and correlations existed for floral, leaf and resource allocation traits, and whether this variation had a genetic component. We also determined the traits which were sexually dimorphic, the degree of dimorphism, and whether it varied among populations. Seven traits exhibited among‐population variation and sexual dimorphism. Variation in the degree of dimorphism occurred only for two traits, suggesting that dimorphism may be evolving more slowly than trait means. Males had more, smaller flowers, shorter leaves, and allocated less of their total biomass to stems and more to leaves than females. Flower production was the most sexually dimorphic trait and was correlated with all measured traits. Most traits exhibited significant correlations between the sexes. The pattern of correlations and the degree of sexual dimorphism among traits lead us to suggest that intrasexual selection for an exaggerated floral display in males has indirectly led to sexual dimorphism in a host of other traits.     

Differences in behavioural traits among native and introduced colonies of an invasive ant

Identifying the factors that promote the success of biological invasions is a key pursuit in ecology. To date, the link between animal personality and invasiveness has rarely been studied. Here, we examined in the laboratory how Argentine ant populations from the species’ native and introduced ranges differed in a suite of behaviours related to species interactions and the use of space. We found correlations among specific behavioural traits that defined an explorative-aggressive syndrome. The Main “European” supercolony (introduced range) more readily explored novel environments, displayed more aggression, detected food resources more quickly, and occupied more space than the Catalonian supercolony (introduced range) and two other Argentine supercolonies (native range). The two native supercolonies also differed in their personalities; one harbouring the less invasive personality, while the other is intermediate between the two introduced supercolonies. Therefore, instead of a binary pattern, Argentine ant supercolonies display a behavioural continuum that is independent on their geographic origin (native/introduced ranges). Our results also suggest that variability in personality traits is correlated to differences in the ecological success of Argentine ant colonies. Differences in group personalities may facilitate the persistence and invasion of animals under novel selective pressures by promoting adaptive behaviours. We stress that the concept of animal personality should be taken into account when elucidating the mechanisms of invasiveness.     

Pigments,Parasites and Personalitiy: Towards a Unifying Role for Steroid Hormones?

A surging interest in the evolution of consistent trait correlations has inspired research on pigment patterns as a correlate of behavioural syndromes, or "animal personalities". Associations between pigmentation, physiology and health status are less investigated as potentially conserved trait clusters. In the current study, lice counts performed on farmed Atlantic salmon Salmo salar naturally infected with ectoparasitic sea lice Lepeophtheirus salmonis showed that individual fish with high incidence of black melanin-based skin spots harboured fewer female sea lice carrying egg sacs, compared to less pigmented fish. There was no significant association between pigmentation and lice at other developmental stages, suggesting that host factors associated with melanin-based pigmentation may modify ectoparasite development to a larger degree than settlement. In a subsequent laboratory experiment a strong negative correlation between skin spots and post-stress cortisol levels was revealed, with less pigmented individuals showing a more pronounced cortisol response to acute stress. The observation that lice prevalence was strongly increased on a fraction of sexually mature male salmon which occurred among the farmed fish further supports a role for steroid hormones as mediators of reduced parasite resistance. The data presented here propose steroid hormones as a proximate cause for the association between melanin-based pigmentation and parasites. Possible fundamental and applied implications are discussed.     

Estimation of environmental and genetic components of quantitative traits with application to serum cholesterol levels.

A mixed model of environmental, polygenic, and major locus effects is developed, allowing for environmental correlations between first-degree relatives and spouses. Maximum-likelihood techniques are used to determine the relative contributions of each of these effects to a quantitative trait. Inclusion of a nuclear family in the sample is assumed to depend on the value of the quantitative trait of one member of the family, so conditional distributions are used. Application of the method to serum cholesterol data from the general population shows that the addition of a polygenic effect to a model that assumes only an environmental effect makes a significant improvement. A completely dominant single gene is also found to be influencing serum cholesterol levels. Although cholesterol levels have been adjusted for a range of factors, such as age, sex, weight/height, and marital status, environmental factors still account for about half the variability in the residual values.     

Examining the link between personality and laterality in a feral guppy Poecilia reticulata population

This study examined whether variation in the strength and direction of lateralization in a detour task was linked with variation in three common personality measurements: boldness, activity and sociability, in a population of wild guppies Poecilia reticulata. Additionally, the aim was to determine whether any consistent correlations between these behavioural traits, known as behavioural syndromes, were present in the study population. The results revealed that all three personality traits were highly repeatable over time in both sexes. Evidence of a complex syndrome in the form of a correlation between boldness, sociability and activity was found; however, this relationship was only present in males. Males that were more active in a familiar environment emerged more quickly from shelter into a novel environment and were more social. In general, male P. reticulata were bold, active and antisocial compared to females, with these differences probably a reflection of opposing life‐history strategies. Only a weak link between the strength of cerebral lateralisation and personality was discovered and this was mediated by sex.     

Schizotypy and behavioural adjustment and the role of neuroticism

Objective

In the present study the relationship between behavioural adjustment following cognitive conflict and schizotypy was investigated using a Stroop colour naming paradigm. Previous research has found deficits with behavioural adjustment in schizophrenia patients. Based on these findings, we hypothesized that individual differences in schizotypy, a personality trait reflecting the subclinical expression of the schizophrenia phenotype, would be associated with behavioural adjustment. Additionally, we investigated whether such a relationship would be explained by individual differences in neuroticism, a non-specific measure of negative trait emotionality known to be correlated with schizotypy.

Methods

106 healthy volunteers (mean age: 25.1, 60% females) took part. Post-conflict adjustment was measured in a computer-based version of the Stroop paradigm. Schizotypy was assessed using the Schizotypal Personality Questionnaire (SPQ) and Neuroticism using the NEO-FFI.

Results

We found a negative correlation between schizotypy and post-conflict adjustment (r = −.30, p<.01); this relationship remained significant when controlling for effects of neuroticism. Regression analysis revealed that particularly the subscale No Close Friends drove the effect.

Conclusion

Previous findings of deficits in cognitive control in schizophrenia patients were extended to the subclinical personality expression of the schizophrenia phenotype and found to be specific to schizotypal traits over and above the effects of negative emotionality.     

Personality and behavioural syndrome in <Emphasis Type="Italic">Necromys lasiurus</Emphasis> (Rodentia: Cricetidae): notes on dispersal and invasion processes

Recent studies showed that behavioural individual features are related to species invasion and occupation abilities. In particular, the recent literature on animal personality has pointed to a correlation between behavioural profiles and the success in different phases of the invasion. In the present study, we investigated personality traits in the Neotropical species Necromys lasiurus. This wild rodent is expanding its original distribution to disturbed areas in the Atlantic Forest biome in response to anthropogenic impacts, acting as an invasive species (broad sense). In order to evaluate personality, we performed three behavioural assays as follows: open field, aversive open field and holeboard field. We extracted three personality domains—activity, exploration, and neophilia—using principal component analysis. There was significant positive correlation between these personality domains characterising a behavioural syndrome. We discussed the implications of this behavioural profile to dispersal and potential invasion abilities in this species.