Effect of body size, age and timing of breeding on clutch and egg size of female Eastern Gray Treefrogs, Hyla versicolor

Information on how organisms allocate resources to reproduction is critical for understanding population dynamics. We collected clutch size (fecundity) and egg size data of female Eastern Gray Treefrogs, Hyla versicolor, and examined whether observed patterns of resource allocation are best explained by expectations arising from life history theory or by expected survival and growth benefits of breeding earlier. Female Hyla versicolor showed high between-individual variation in clutch and egg size. We did not observe maternal allocation trade-offs (size vs number; growth vs reproduction) predicted from life history theory, which we attribute to the large between-female variation in resource availability, and the low survival and post-maturity growth rate observed in the study population. Rather, clutches are larger at the beginning of the breeding season, and this variation in reproductive investment aligns with seasonal variation in ecological factors affecting offspring growth and survival.

The influence of harshness and unpredictability on female sexual development: Addressing gene–environment interplay using a polygenic score

Recent developments in the application life history theory to human development indicate two fundamental dimension of the early environment – harshness and unpredictability – are key regulators life history strategies. Few studies have examined the manner with which these dimensions influence development, though age at menarche (AAM) and age at first sexual intercourse have been proposed as possible mechanisms among women. Data from the Avon Longitudinal Study of Parents and Children (N = 3,645) were used to examine direct and indirect effects of harshness (financial difficulties) and unpredictability (paternal transitions) on lifetime and past year sexual partners during adolescence and young adulthood. Genetic confounding was addressed using an AAM polygenic score (PGS) and potential gene-by-environment interactions were also evaluated using the PGS. Path model results showed only harshness was directly related to AAM. Harshness, unpredictability, and AAM were indirectly related to lifetime and past year sexual partner number via age at first sexual intercourse. The PGS did not account for any of the associations and no significant interactions were detected. Implications of these results for developmental models derived from life history theory are discussed as well as the role of PGSs in gene–environment interplay research.

The effects of childhood unpredictability and harshness on emotional control and relationship quality: A life history perspective

Being able to control oneself in emotionally upsetting situations is essential for good relationship functioning. According to life history theory, childhood exposure to harshness and unpredictability should forecast diminished emotional control and lower relationship quality. We examined this in three studies. In Studies 1 and 2, greater childhood unpredictability (frequent financial, residential, and familial changes), but not harshness (low SES), was associated with lower emotional control in adolescents (N = 1041) and adults (N = 327). These effects were stronger during the participants’ reproductive years. Moreover, in Study 2, greater childhood unpredictability was indirectly associated with lower relationship quality through lower emotional control. In study 3, we leveraged the Minnesota Longitudinal Study of Risk and Adaptation (N = 160). Greater early-life unpredictability (ages 0–4) prospectively predicted lower relationship quality at age 32 via lower emotional control at the same age. This relation was serially mediated by less supportive observed early maternal care (ages 1.5–3.5) and insecure attachment representations (ages 19 and 26). Early unpredictability also predicted greater observed emotional distress during conflict interactions with romantic partners (ages 19–36). These findings point to the role of emotional control in mediating the effects of unpredictable childhood environments on relationship functioning in adulthood.

Not all traits are functional: the Panglossian paradigm

The popularity of trait-based approaches continues to rise despite challenges in identifying strong links between traits and organism performance. Here, we summarise evidence demonstrating that not all traits appear to be functional, and discuss how life history theory and demography can help elucidate which, how, where, and when traits gain functionality

Reproductive timing and investment decisions of a protogynous hermaphroditic coral reef fish species

<p>Life-history theory suggests that an organism must balance its available energy between two competing physiological processes to maximize fitness: reproduction and somatic growth. Energetic trade-offs are a fundamental concept of life history theory and form the basis of intra- and inter-specific variation in life-history strategies. In fishes, reproduction-growth trade-offs are an essential component of life-history optimization. This is particularly true for species with protogynous sex- change (the most common reproductive mode among coral reef fish species), where reproductive success rapidly and disproportionally increases with body size/ corresponding social status. In such systems, lifetime fitness is inherently linked to patterns of growth and energy allocation strategies determined by an individual’s size-specific rank within the dominance hierarchy. However, energy allocation strategies in a protogynous species may not only be a function of body size. Coral reef fish species are exposed to extremely variable environmental conditions and this can favour the evolution of strategies that utilize good times and avoid disadvantageous times for reproduction. Consequently, size- specific parental investment decisions may vary greatly in time and space according to environmental cues. My thesis focuses on the protogynous reef fish, Thalassoma hardwicke (the sixbar wrasse), which is extremely abundant on shallow coral reefs throughout the Indo-Pacific region. Specifically, I evaluate patterns of spawning and reproductive investment as a function of body size, social status, lunar phase and other environmental parameters. I address the question of whether females/males of differing size make different fitness-related decisions when away from spawning sites, and I evaluate context-dependency in these decisions. Finally, I will attempt to reconstruct the developmental histories (e.g., larval growth rates) of individuals from otoliths to evaluate potential relationships between developmental histories and fitness attributes.</p>

Reproductive timing and investment decisions of a protogynous hermaphroditic coral reef fish species

<p>Life-history theory suggests that an organism must balance its available energy between two competing physiological processes to maximize fitness: reproduction and somatic growth. Energetic trade-offs are a fundamental concept of life history theory and form the basis of intra- and inter-specific variation in life-history strategies. In fishes, reproduction-growth trade-offs are an essential component of life-history optimization. This is particularly true for species with protogynous sex- change (the most common reproductive mode among coral reef fish species), where reproductive success rapidly and disproportionally increases with body size/ corresponding social status. In such systems, lifetime fitness is inherently linked to patterns of growth and energy allocation strategies determined by an individual’s size-specific rank within the dominance hierarchy. However, energy allocation strategies in a protogynous species may not only be a function of body size. Coral reef fish species are exposed to extremely variable environmental conditions and this can favour the evolution of strategies that utilize good times and avoid disadvantageous times for reproduction. Consequently, size- specific parental investment decisions may vary greatly in time and space according to environmental cues. My thesis focuses on the protogynous reef fish, Thalassoma hardwicke (the sixbar wrasse), which is extremely abundant on shallow coral reefs throughout the Indo-Pacific region. Specifically, I evaluate patterns of spawning and reproductive investment as a function of body size, social status, lunar phase and other environmental parameters. I address the question of whether females/males of differing size make different fitness-related decisions when away from spawning sites, and I evaluate context-dependency in these decisions. Finally, I will attempt to reconstruct the developmental histories (e.g., larval growth rates) of individuals from otoliths to evaluate potential relationships between developmental histories and fitness attributes.</p>

Life history strategy and overeating during COVID-19 pandemic: a moderated mediation model of sense of control and coronavirus stress

Background This study examined the mediating effect of sense of control and the moderating effect of coronavirus stress on the relationship between life history strategy and overeating among Chinese college students during the COVID-19 period. Methods 3310 Chinese students (Mage = 19.74, SD = 1.50; 47% males) completed self-reported questionnaires regarding life history strategy, sense of control, overeating, and coronavirus stress. The data were analyzed using Pearson’s r correlations and moderated mediation analysis. Results The results revealed that control sense mediated the link between life history strategy and college students’ overeating. College students’ coronavirus stress moderated the associations between life history strategy and college students’ sense of control and between control sense and overeating. The association between life history strategy and sense of control was stronger for those with lower coronavirus stress, and the association between sense of control and overeating was stronger for those with lower coronavirus stress. Conclusions This study identified that the critical factors were associated with overeating. On the one hand, the research deepens the application and interpretation of life history theory in the field of eating; on the other hand, it provides evidence for the prevention of overeating, and provides theoretical basis for psychological assistance among Chinese college students.

Women’s Trade-Offs between Fertility and Employment during Industrialisation

Modelling fertility decline in post-industrial populations in the context of life history theory has allowed us to better understand the environmental pressures that shape reduced family size. One such pressure, which has received relatively little attention from ecologists, is the movement of women into the labour market. Analyses of effects of employment on fertility in contemporary developing or post-demographic transition populations are limited by the widespread use of modern contraceptives: while uptake of these methods may be a mechanism by which reduced fertility is enacted, their use may obscure effects of employment on fertility. Here, we investigated the impact of women’s employment on family size during a period of the movement of women into the workforce but prior to the use of modern contraceptives. We analysed the effects of women’s employment on family size using census records from 1901 for a regional-level analysis of parishes in Scotland, and for 1851–1901 for an individual-level analysis of the Scottish city of Dundee. Women in employment had fewer children than those not in employment. Income was inversely related with family size, and this was independent of the effects of women’s employment on family size. We suggest that female employment contributes to the evolution of smaller family sizes and that this takes place in the context of prevailing and emerging gender roles, and in interaction with opportunities for employment and wealth.

Perceptions of procedural justice and police legitimacy: A life history perspective

<p>Prior research on attitudes towards the police has largely focused on the relationship between demographic factors and perceptions of the police. These studies have produced inconclusive results, and there is no general consensus why and how demographic factors account for individual differences in attitudes towards the police. Life history theory, a “middle-level” evolutionary theory, is one that has largely been neglected in mainstream criminology, but has been used in the current research to explain individual differences in attitudes towards the police. Two studies, both using an online survey, were conducted to explore the extent to which life history strategy explained individual attitudes towards procedural justice, police legitimacy and police socialization after controlling for demographic factors, previous police interaction and prior arrest. Study one, a university sample of 305 participants and study two, a general population sample of 75 Wellington residents both found support for the application of life history theory being used to explain individual differences in attitudes towards the police. Overall, the current research showed that those with a slower life history strategy were more likely hold more positive perceptions of police legitimacy, procedural justice and police socialization regardless of demographic factors, previous police interaction, and prior arrest.</p>