Sex-biased demography modulates male harm across the genome

Recent years have seen an explosion of theoretical and empirical interest in the role that kin selection plays in shaping patterns of sexual conflict, with a particular focus on male harming traits. However, this work has focused solely on autosomal genes, and as such it remains unclear how demography modulates the evolution of male harm loci occurring in other portions of the genome, such as sex chromosomes and cytoplasmic elements. To investigate this, we extend existing models of sexual conflict for application to these different modes of inheritance. We first analyse the general case, revealing how sex-specific relatedness, reproductive value and the intensity of local competition combine to determine the potential for male harm. We then analyse a series of demographically explicit models, to assess how dispersal, overlapping generations, reproductive skew and the mechanism of population regulation affect sexual conflict across the genome, and drive conflict between nuclear and cytoplasmic genes. We then explore the effects of sex biases in these demographic parameters, showing how they may drive further conflicts between autosomes and sex chromosomes. Finally, we outline how different crossing schemes may be used to identify signatures of these intragenomic conflicts.

What is the best fitness measure in wild populations? A case study on the power of short-term fitness proxies to predict reproductive value

Fitness is at the core of evolutionary theory, but it is difficult to measure accurately. One way to measure long-term fitness is by calculating the individual’s reproductive value, which represents the expected number of allele copies an individual passes on to distant future generations. However, this metric of fitness is scarcely used because the estimation of individual’s reproductive value requires long-term pedigree data, which is rarely available in wild populations where following individuals from birth to death is often impossible. Wild study systems therefore use short-term fitness metrics as proxies, such as the number of offspring produced. This study obtained three frequently used short-term proxies for fitness obtained at different offspring life stages (eggs, hatchlings, fledglings and recruits), and compared their ability to predict reproductive values derived from the genetic pedigree of a wild passerine bird population. We used twenty years of precise field observations and a near-complete genetic pedigree to calculate reproductive success, individual growth rate and de-lifed fitness as lifetime fitness measures, and as annual de-lifed fitness. We compared the power of these metrics to predict reproductive values and lineage survival to the end of the study period. The three short-term fitness proxies predict the reproductive values and lineage survival only when measured at the recruit stage. There were no significant differences between the different fitness proxies at the same offspring stages in predicting the reproductive values and lineage survival. Annual fitness at one year old predicted reproductive values equally well as lifetime de-lifed fitness. However, none of the short-term fitness proxies was strongly associated with the reproductive values. In summary, the commonly short-term fitness proxies capture long-term fitness with intermediate accuracy at best, if measured at recruitment stage. As lifetime fitness measured at recruit stage and annual fitness in the first year of life were the best proxies of long-term fitness, we encourage their future use.

Evolutionary Perspectives on Maternal Parenting

This chapter focuses on maternal care, including the specialized psychological mechanisms designed to shape maternal solicitude and the various factors to which these mechanisms are sensitive. It identifies factors that influence levels of maternal parental investment. Maternal factors that lead to increased investment include the amount of resources available, potential for future mating opportunities and maternal age, and number of offspring. Child factors that lead to greater investment include reproductive value, age of the child, sex, offspring need, and relatedness to the mother. Although there has been an abundance of research on maternal parental investment, most of the studies have focused on individual factors that influence parental investment levels with only a few investigating interactive models. Therefore, more research investigating interactive models is necessary to better understand under which circumstances mothers would be more or less likely to invest in their offspring.

Reproductive value and analyses of population dynamics of age-structured populations

Many populations of especially long-lived species show large temporal variation in age structure, which can complicate estimating of important population parameters. This occurs because it can be difficult to disentangle whether variation in numbers is due to fluctuations in the environment or caused by changes in the age distribution. This chapter shows that fluctuations in the total reproductive value of the population, that is, the sum of all individual reproductive values, often provide a good description of the population dynamics but still is not confounded by fluctuations in age structure. Because the change in the total reproductive rate is exactly equal to the growth rate of the population, this quantity enables decomposition of the long-run growth rate into stochastic components caused by age-specific variation in demographic and environmental stochasticity. The chapter illustrates the practical application of this approach in stochastic demography by analyses of the dynamics of several populations of birds and mammals. It puts a strong focus on these methods being particularly useful in viability analyses of small populations of vulnerable or endangered species.

A Systematic Review of Evolutionary-Based Conceptualisations of Family Violence and the Development of an Alternative Motivational-Emotional Systems Approach

<p>Evolutionary psychology is a field that provides distal explanations of behaviour. Although it has potential to enhance current understandings of family violence, the present state of the literature is conceptually messy. The aim of the current thesis was to bring coherence to this domain by conducting a systematic review of evolutionary conceptualisations of family violence over the past four decades. Four databases (PsycINFO, PsycArticles, ProQuest Central, and Web of Science) were searched using relevant search terms to identify any work that examined family violence from an evolutionary perspective. A total of 54 publications were included in the review, ranging from theoretical pieces and empirical studies through to several commentaries. Findings indicated family violence was conceptualised as an adaptation, by-product, or pathology. However, numerous authors had contradictory perspectives as to how certain offences should be conceptualised, others failed to make a conceptual claim at all, and there was a tendency among authors to describe the behaviour as an adaptation rather than the underlying psychological mechanisms. To make sense of the findings, six recurrent themes were developed: lack of resources, genetic relatedness as a protective factor, fast life history strategy, reproductive value, lethal violence as pathology, and male sexual and familial proprietariness. The second aim of the thesis was to develop a novel theoretical framework that conceptualised family violence in a more clear and coherent manner. This new model was labelled the Fundamental Motives Framework and mapped findings from the systematic review onto a range of motivational-emotional systems. The Fundamental Motives Framework was discussed as a promising way of providing a multi- faceted, coherent perspective of family violence that accommodates for the heterogeneity in offending. Limitations and directions for future research were also discussed.</p>

A Systematic Review of Evolutionary-Based Conceptualisations of Family Violence and the Development of an Alternative Motivational-Emotional Systems Approach

<p>Evolutionary psychology is a field that provides distal explanations of behaviour. Although it has potential to enhance current understandings of family violence, the present state of the literature is conceptually messy. The aim of the current thesis was to bring coherence to this domain by conducting a systematic review of evolutionary conceptualisations of family violence over the past four decades. Four databases (PsycINFO, PsycArticles, ProQuest Central, and Web of Science) were searched using relevant search terms to identify any work that examined family violence from an evolutionary perspective. A total of 54 publications were included in the review, ranging from theoretical pieces and empirical studies through to several commentaries. Findings indicated family violence was conceptualised as an adaptation, by-product, or pathology. However, numerous authors had contradictory perspectives as to how certain offences should be conceptualised, others failed to make a conceptual claim at all, and there was a tendency among authors to describe the behaviour as an adaptation rather than the underlying psychological mechanisms. To make sense of the findings, six recurrent themes were developed: lack of resources, genetic relatedness as a protective factor, fast life history strategy, reproductive value, lethal violence as pathology, and male sexual and familial proprietariness. The second aim of the thesis was to develop a novel theoretical framework that conceptualised family violence in a more clear and coherent manner. This new model was labelled the Fundamental Motives Framework and mapped findings from the systematic review onto a range of motivational-emotional systems. The Fundamental Motives Framework was discussed as a promising way of providing a multi- faceted, coherent perspective of family violence that accommodates for the heterogeneity in offending. Limitations and directions for future research were also discussed.</p>

Lineage-based differences in grandparental investment according to adverse early life experiences of grandchildren

Evolutionary theory predicts a downward flow of investments from older to younger generations that represents individuals’ efforts to maximize their inclusive fitness. Maternal grandparents and maternal grandmothers in particular have been consistently found to show the highest investment (e.g., time, care and resources) in their grandchildren. However, grandparental investment may depend on varying social and environmental conditions affecting the development of children, modifying the benefits and costs of grandparental investment. Using population-based survey data of English and Welsh adolescents, the present study investigates whether grandparental investment responds to adverse early life experiences (AELEs) of grandchildren. In contrast to current literature that considers grandparental investment in response to AELEs from the perspective of increased investment to meet the increased need, we predict that higher number of AELEs are associated with reduced grandparental investment as increased AELEs tend to reduce the reproductive value of grandchildren. Moreover, we predict that those grandparents who already invest less (i.e., paternal grandparents) react more strongly to elevated AELEs compared to those grandparents who invest the most (i.e., maternal grandparents and maternal grandmothers in particular). We found support for our predictions that maternal grandparents (maternal grandmothers in particular) showed investment in grandchildren that was unrelated to their grandchildren’s AELEs. In contrast, paternal grandparents reduced their investment in grandchildren in cases of increased AELEs. These findings were largely robust to measurement error in the of AELEs and confounding due to omitted shared causes.

Caste development and sex ratio of the Ryukyu drywood termite Neotermes sugioi and its potential mechanisms

Sex allocation is one of the most studied traits in evolutionary biology because its theoretical predictions match the empirical data. Here, using the Ryukyu dry-wood termite Neotermes sugioi, we investigated several factors that could bias the sex allocation in three populations (Okinawa, Ishigaki/Iriomote, and Yonaguni). Our survey showed that there were more queen-only colonies than king-only colonies in these populations, suggesting a longer lifespan of the queens than that of the kings. In this condition, sex-asymmetric reproductive value (SRV) theory predicts female bias, because even after the short-lived kings die, the long-lived queens can continue reproduction with their sons. However, sex allocation in this species seemed to be biased toward males. Furthermore, we examined the possibility of intrasexual competition among siblings (ICS). If ICS is the cause of the bias, the allocation is expected to change depending on the total investment in sexual offspring. However, the biomass of both male and female alates increased linearly with the increase in the total biomass of the alates in these populations. Thus, neither the SRV nor the ICS theory could explain the male-biased sex ratio of N. sugioi. On the basis of these results, we discuss the remaining possibilities in this species.