The heritability of life history strategy: The k‐factor,covitality, and personality

Abstract

Archival data from the MIDUS survey (Brim et al., 2000), a nationally representative sample, on 309 MZ and 333 DZ twin pairs aged 25–74 years were used to test the psychometrics and behavioral genetics of life history strategy. We organized 253 of the originally administered 2,000 questions into 30 scales measuring life history traits (e.g., quality of family relationships and altruism towards kin), medical symptoms (e.g., thyroid problems), personality traits (e.g., neuroticism, extraversion, conscientiousness), and social background (e.g., financial security). A single higher‐order factor, indicating a general life history strategy, composed of three lower‐order factors, was replicated. Factor analyses were then performed on the genetic variance‐covariance matrices. We found that (a) a single higher‐order factor explained the preponderance of the genetic correlations among the scales and (b) this higher‐order factor was itself 68 percent heritable and accounted for 82 percent of the genetic variance among the three component lower‐order factors.     

The K-factor,Covitality, and personality

We present a psychometric test of life history theory as applied to human individual differences using MIDUS survey data (Brim et al. 2000). Twenty scales measuring cognitive and behavioral dimensions theoretically related to life history strategy were constructed using items from the MIDUS survey. These scales were used to construct a single common factor, the K-factor, which accounted for 70% of the reliable variance. The scales used included measures of personal, familial, and social function. A second common factor, Covitality, was constructed from scales for physical and mental health. Finally, a single general factor, Personality, was constructed from scales for the “Big Five” factors of personality. The K-factor, covitality factor, and general personality factor correlated significantly with each other, supporting the prediction that high K predicts high somatic effort and also manifests in behavioral display. Thus, a single higher-order common factor, the Super-K factor, was constructed that consisted of the K-factor, covitality factor, and personality factor.     

The contribution of additive genetic variation to personality variation: heritability of personality

Individual animals frequently exhibit repeatable differences from other members of their population, differences now commonly referred to as ‘animal personality’. Personality differences can arise, for example, from differences in permanent environmental effects―including parental and epigenetic contributors―and the effect of additive genetic variation. Although several studies have evaluated the heritability of behaviour, less is known about general patterns of heritability and additive genetic variation in animal personality. As overall variation in behaviour includes both the among-individual differences that reflect different personalities and temporary environmental effects, it is possible for personality to be largely genetically influenced even when heritability of behaviour per se is quite low. The relative contribution of additive genetic variation to personality variation can be estimated whenever both repeatability and heritability are estimated for the same data. Using published estimates to address this issue, we found that approximately 52% of animal personality variation was attributable to additive genetic variation. Thus, while the heritability of behaviour is often moderate or low, the heritability of personality is much higher. Our results therefore (i) demonstrate that genetic differences are likely to be a major contributor to variation in animal personality and (ii) support the phenotypic gambit: that evolutionary inferences drawn from repeatability estimates may often be justified.     

The microbiota influences the Drosophila melanogaster life history strategy

Organisms are locally adapted when members of a population have a fitness advantage in one location relative to conspecifics in other geographies. For example, across latitudinal gradients, some organisms may trade off between traits that maximize fitness components in one, but not both, of somatic maintenance or reproductive output. Latitudinal gradients in life history strategies are traditionally attributed to environmental selection on an animal's genotype, without any consideration of the possible impact of associated microorganisms (“microbiota”) on life history traits. Here, we show in Drosophila melanogaster, a key model for studying local adaptation and life history strategy, that excluding the microbiota from definitions of local adaptation is a major shortfall. First, we reveal that an isogenic fly line reared with different bacteria varies the investment in early reproduction versus somatic maintenance. Next, we show that in wild fruit flies, the abundance of these same bacteria was correlated with the latitude and life history strategy of the flies, suggesting geographic specificity of the microbiota composition. Variation in microbiota composition of locally adapted D. melanogaster could be attributed to both the wild environment and host genetic selection. Finally, by eliminating or manipulating the microbiota of fly lines collected across a latitudinal gradient, we reveal that host genotype contributes to latitude‐specific life history traits independent of the microbiota and that variation in the microbiota can suppress or reverse the differences between locally adapted fly lines. Together, these findings establish the microbiota composition of a model animal as an essential consideration in local adaptation.     

Egg dumping and life history strategy of Callosobruchus maculatus

Abstract.  Previous studies have demonstrated that female Callosobruchus maculatus adjust oviposition rates to cope with changes in host availability. A female lays fewer eggs when host availability is low, and hence decreases larval competition. However, females will also dump eggs on unsuitable substrates under conditions of host deprivation. Because the female does not feed as an adult, egg dumping possibly wastes energy and may thus be a maladaptive behaviour. In this study, the effect of mating and age on the egg-dumping behaviour and the life history strategy of the female are explored. Under host-deprived conditions, mating is seen to trigger egg-dumping behaviour. Also, females mated at 6 days dump significantly fewer eggs and live longer than females mated at 0 or 3 days. Thus, a trade-off between fecundity and longevity is seen among females subjected to different manipulations. In addition, 6-day-old virgin females contain more mature eggs than females mated at 6 days can produce when deprived of hosts. This finding indicates that the female reallocates internal energy resources by oosorption in a resource-limited environment. To test the maladaptive hypothesis, mated females were deprived of a host for 6 days and then given sufficient hosts each day. The results show that the more eggs dumped by a female in the first 6 days, the more eggs are laid later on beans. Egg dumping is thus not maladaptive.     

Fecundity, offspring longevity, and assortative mating: parametric tradeoffs in sexual and life history strategy

Genetic diversification of offspring represents a bet-hedging strategy that evolved as an adaptation to unpredictable environments. The benefits of sexual reproduction come with severe costs. For example, each offspring only carries half of each parent's genetic makeup through direct descent. The lower the reproductive rate, the more substantial the cost when considering the proportion of genes represented in subsequent generations. Positive assortative mating represents a conservative bet-hedging strategy that offsets some of these costs and preserves coadapted genomes in stable and predictable environments, whereas negative assortative mating serves the inverse function of genetic diversification in unstable and unpredictable environments.     

The meanings of weaning: Growth,lactation, and life history

Hooded seal pups are suckled for a total of four days; chimpanzees and elephants sometimes are suckled for as long as eight years. This enormous range suggests considerable diversity in reproductive strategies. Lactation represents early maternal effort, whereas weaning is the infant's transition to nutritional independence. Weaning behavior is thus important from two interconnected perspectives: that of the infant during this transition and that of the mother with the cessation of lactation and the resumption of her reproductive capacity. What controls such diversity in the duration of lactation? What are the consequences of this diversity for mothers in terms of reproduction and for infants in terms of their growth and survival? How are differences in lactation reflected in behavioral interactions? The answers to these questions involve consideration of weaning and growth, and have implications for life histories.     

Allozyme heterozygosity, date of first feeding and life history strategy in Atlantic salmon

The relations between allozyme heterozygosity, relative date of first feeding and life history strategy in juvenile Atlantic salmon Salmo salar were examined using eggs obtained from a 400 family cross (20 male × 20 female adult Atlantic salmon). Multilocus heterozygosity, through its positive associations with the timing of first feeding and growth rate, was correlated with life history strategy in juvenile Atlantic salmon, albeit under genotype × environmental (temperature, food availability) regulation. Under hatchery conditions, a 10 day difference was observed in the relative date of first feeding between early and late first feeding Atlantic salmon. Early first feeding Atlantic salmon exhibited a significantly higher mean heterozygosity, grew faster at ambient water temperature (April to November) and a significantly higher proportion adopted the early freshwater maturation (age 0+ years, male fish) or early migrant (age 1+ years, mainly female fish) strategies compared to late first feeding Atlantic salmon. Elevated water temperatures over the winter (December to April, >10·5° C) provided additional growth opportunity allowing previously mature male parr (mainly early first feeders) and lower modal group parr (mainly late first feeders) to adopt the early migrant strategy by the following spring.     

The population dynamics, reproductive strategy and life history tactics of Musculium lacusfre (Bivalvia: Pisidiidae) in Hong Kong

Hitherto uninvestigated in Hong Kong are the population dynamics, reproductive strategies and life history tactics of the Pisidiidae of which three species are known to occur locally. This study is of Musculium lacustre inhabiting a drainage ditch of the Lam Tsuen River in the New Territories of Hong Kong and extended over 15 months during 1983–84.
In Hong Kong, M. lacustre is a protandric, simultaneous hermaphrodite that matures at a length of 2 mm; the majority of each generation is, however, not mature until a length of between 4–6 mm is attained. Fertilized eggs are brooded in the inner demibranchs until they reach a length of 1.5 mm when they are released as post-foetal larvae. Musculium lacustre is univoltine. Reproduction occurs twice a year but, since M. lacustve is semelparous, the population contains, at any one time, two overstepping generations. Thus, a spring generation is recruited and grows rapidly to generate a second, smaller, autumn generation. This in turn grows rapidly and matures to produce the spring generation of the succeeding year. Adult mortality occurs in late summer and winter. A few of the late-born spring generation may overwinter to contribute to the spring generation of the succeeding year. This is not so with the autumn generation.
Such sexual and life history tactics can be related to the climate and hydrology of Hong Kong and its freshwater habitats. Reproduction takes place in spring and autumn when temperatures are moderate. Mortality is high in summer and winter when the habitat is either, respectively, hot and flushed out by summer rains or cold and dry. As M. larustre is able to overwinter but not aestivate at these latitudes (22° N), it is postulated that this holarctic species is approaching the southern limit of its asiatic range. Musculium larustre is compared with the other bivalves inhabiting fresh and brackish-water habitats in southern China.     

Energy allocation and life history strategy of the desert isopod H. reaumuri

Summary Population characteristics of the desert isopod H. reaumuri and its energy allocation during each penophase were investigated in the Negev desert, Israel.It was found that on the individual level, 52% of the energy is allocated to the prereproductive, and 48% to the reproductive phenophases. On the population level, only 10–23% is devoted to isopods which are involved in reproduction. Assuming that the energy allocation pattern in H. reaumuri is the consequence of its life history strategy, two unique evolutionary lines were suggested. One suggestion is the evolution of the family mode of life which increases the probability of the individual's survival. This is due to parental investment and co-operation between siblings. The other suggestion is the evolution of high energy utilization for burrowing, in order to solve the low and unpredictable nature of water resources in the desert.     

Change across the lifespan in a psychological measure of life history strategy

Life history theory predicts that people calibrate their reproductive strategies to local levels of environmental harshness and unpredictability. While previous research has established the importance of early life cues in the development of life history strategy, the degree to which life history strategy exhibits plasticity later in life is unclear. Using longitudinal data (total N = 479) from four archival studies and a recently validated psychological measure of life history strategy, we examined mean-level trends in life history strategy at the level of psychological phenotype between the ages of 7 and 60 and found that life history strategy slowed down linearly as a function of age. Highlighting the importance of sexual selection in shaping life history strategy, we also found that men had a faster life history strategy than women at all ages and that the magnitude of this difference was constant across the lifespan. Our findings suggest that life history strategy development continues even in older adulthood. We discuss the possibility that this occurs in response to the accumulation of biological and social (e.g. offspring, relationships) capital and information about local risks and incentives.     

Using monozygotic twin differences to examine the relationship between parental affection and personality: a life history account

The relationship between maternal and paternal affection, reported in adulthood, and personality was examined using a genetically sensitive research design comparing differences between monozygotic twins. Using life history theory as a framework, it was predicted that differences in maternal and paternal affection would be predictive of differences in personality such that the twin reporting greater maternal and paternal affection would also report a personality profile reflective of a slow life history strategy. Specifically, it was predicted that the twin that reported greater maternal and paternal affection would also score high on the meta-traits of plasticity, stability, and the general factor of personality (GFP). The results supported the hypotheses, with most variance accounted for by the GFP. Additional results suggest that differences in paternal affection exhibit a stronger effect and that stability and plasticity may provide unique information about the association between differences in parental affection and differences in personality. Attachment and parental investment theories offer possible explanations for the findings, although alternative explanations are also proffered. It may also be beneficial for future research using a monozygotic twin difference approach to utilize biometric measures of life history strategy.     

Ecological volatility and human evolution: A novel perspective on life history and reproductive strategy

Humans are characterized by a suite of traits that seem to differentiate them profoundly from closely related apes such as the gorilla, chimpanzee, and orang‐utan. These traits include longevity, cooperative breeding, stacking of offspring, lengthy maturation, and a complex life‐course profile of adiposity. When, how, and why these traits emerged during our evolutionary history is currently attracting considerable attention. Most approaches to life history emphasize dietary energy availability and the risk of mortality as the two key stresses shaping life‐history variability between and within species. The high energy costs of the large Homo brain are also seen as the central axis around which other life‐history traits were reorganized. I propose that ecological volatility may have been a key stress, selecting in favor of the suite of traits in order to tolerate periods of energy scarcity, and increase reproductive output during periods of good conditions. Theses life‐history adaptations may have preceded and enabled the trend toward encephalization. © 2012 Wiley Periodicals, Inc.     

试论麦类作物非水力根信号与生活史对策

从植物非水力根信号的生理调节作用和生活史进化解度看,在水分亏缺条件下,自然选择会导致植物产生大量根系以增加对水分的竞争能力,而浅根系则可在干旱来临时,以快速反应的根信号来调节和平衡植株水分状况,度过干旱时期。但是,自然选择压力下的植物特征往往不利于作物籽粒产量这一种群水平上的属性的改善。作物产量的提高过程是一个不断加强的人工选择过程。在作物生产中,作物水环境得到了改善,强大的多年生竞争者基本消失,     

Robustness of ancestral state estimates: evolution of life history strategy in ichneumonoid parasitoids

We test hypotheses for the evolution of a life history trait among a group of parasitoid wasps (Hymenoptera: Ichneumonoidea), namely, the transition among koinobiont parasitoids (parasitoids whose hosts continue development after oviposition) between attacking exposed hosts and attacking hosts that are concealed within plant tissue. Using a range of phylogeny estimates based on 28S rDNA sequences, we use maximum parsimony (MP) and maximum likelihood (ML) methods to estimate the ancestral life history traits for the main clades in which both traits occur (using the programs MacClade and Discrete, respectively). We also assess the robustness of these estimates; for MP, we use step matrices in PAUP* to find the minimum weight necessary to reverse estimates or make them ambiguous, and for ML, we measure the differences in likelihood after fixing the ancestral nodes at the alternative states. We also measure the robustness of the MP ancestral state estimate against uncertainties in the phylogeny estimate, manipulating the most-parsimonious tree in MacClade to find the shortest suboptimal tree in which the ancestral state estimate is reversed or made ambiguous. Using these methods, we find strong evidence supporting two transitions among koinobiont Ichneumonoidea: (1) to attacking exposed hosts in a clade consisting of the Helconinae and related subfamilies, and (2) the reverse transition in a clade consisting of the Euphorinae and related subfamilies. In exploring different methods of analyzing variable-length DNA sequences, we found that direct optimization with POY gave some clearly erroneous results that had a profound effect on the overall phylogeny estimate. We also discuss relationships within the superfamily and expand the Mesostoinae to include all the gall-associated braconids that form the sister group of the Aphidiinae.