Personality matters : exploring the relationship between personality and stress physiology in captive African lions

Background: Considering animals as individuals and not as species is becoming increasingly essential to animal welfare management in captive settings. Recent studies on big cat personalities and coping strategies suggest personality can help big cats cope in their surroundings. Yet a large portion of the published literature focuses on understanding either the personality or stress physiology of big cats. Our research shows how integrating an improved understanding of the personality of big cats with stress physiology may enhance welfare, especially for endangered species like African lions. By using a wild cat personality checklist, this study compared the key personality dimensions of 22 African lions with its faecal glucocorticoids and assessed factors influencing their personality and stress physiology. Results: We found two reliable personality dimensions for African lions (dominance and agreeableness) and identified key factors (sex, age and location) that may influence their personality. Further, on testing if these factors influenced the stress physiology through variations in glucocorticoid levels, there was no significant difference. However, there was a strong negative association between agreeableness and glucocorticoid levels. These results suggest that the behavioural traits loading positively and higher for agreeableness are associated with lower glucocorticoid stress levels, which may assist a lion to cope with stressors in its surroundings. Conclusions: Our findings highlight this integrated approach of linking personality and stress physiology of big cats can be beneficial for caretakers. For example, during stressful veterinary procedures or in reintroduction programs, recognizing the personality of lions can help in designing or providing them with resources that will alleviate stress. Thus, there is a need for more interdisciplinary approaches that will contribute towards enhancing the individual and overall welfare of big cats

Genetic covariance in immune measures and pathogen resistance in decorated crickets is sex and pathogen specific

Insects are important models for studying immunity in an ecological and evolutionary context. Yet, most empirical work on the insect immune system has come from phenotypic studies meaning we have a limited understanding of the genetic architecture of immune function in the sexes. We use nine highly inbred lines to thoroughly examine the genetic relationships between a suite of commonly used immune assays (haemocyte count, implant encapsulation, total phenoloxidase activity, antibacterial zone of inhibition and pathogen clearance) and resistance to infection by three generalist insect pathogens (the gram-negative bacterium Serratia marcescens, the gram-positive bacterium Bacillus cereus and the fungus Metarhizium robertsii) in male and female Gryllodes sigillatus. There were consistent positive genetic correlations between haemocyte count, antibacterial and phenoloxidase activity and resistance to S. marcescens in both sexes, but these relationships were less consistent for resistance to B. cereus and M. robertsii. In addition, the clearance of S. marcescens was genetically correlated with the resistance to all three pathogens in both sexes. Genetic correlations between resistances to the different pathogen species were inconsistent, indicating that resistance to one pathogen does not necessarily mean resistance to another. Finally, while there is ample genetic (co)variance in immune assays and pathogen resistance, these genetic estimates differed across the sexes and many of these measures were not genetically correlated across the sexes, suggesting that these measures could evolve independently in the sexes. Our finding that the genetic architecture of immune function is sex and pathogen specific suggests that the evolution of immune function in male and female G. sigillatus is likely to be complex. Similar quantitative genetic studies that measure a large number of assays and resistance to multiple pathogens in both sexes are needed to ascertain if this complexity extends to other species

Active and covert infections of cricket Iridovirus and Acheta domesticus Densovirus in reared Gryllodes sigillatus crickets

Interest in developing food, feed, and other useful products from farmed insects has gained remarkable momentum in the past decade. Crickets are an especially popular group of farmed insects due to their nutritional quality, ease of rearing, and utility. However, production of crickets as an emerging commodity has been severely impacted by entomopathogenic infections, about which we know little. Here, we identified and characterized an unknown entomopathogen causing mass mortality in a lab-reared population of Gryllodes sigillatus crickets, a species used as an alternative to the popular Acheta domesticus due to its claimed tolerance to prevalent entomopathogenic viruses. Microdissection of sick and healthy crickets coupled with metagenomics-based identification and real-time qPCR viral quantification indicated high levels of cricket iridovirus (CrIV) in a symptomatic population, and evidence of covert CrIV infections in a healthy population. Our study also identified covert infections of Acheta domesticus densovirus (AdDNV) in both populations of G. sigillatus. These results add to the foundational research needed to better understand the pathology of mass-reared insects and ultimately develop the prevention, mitigation, and intervention strategies needed for economical production of insects as a commodity

Evolution of immune function in response to dietary macronutrients in male and female decorated crickets

Although dietary macronutrients are known to regulate insect immunity, few studies have examined their evolutionary effects. Here, we evaluate this relationship in the cricket Gryllodes sigillatus by maintaining replicate populations on four diets differing in protein (P) to carbohydrate (C) ratio (P- or C-biased) and nutritional content (low- or high-nutrition) for >37 generations. We split each population into two; one maintained on their evolution diet and the other switched to their ancestral diet. We also maintained populations exclusively on the ancestral diet (baseline). After three generations, we measured three immune parameters in males and females from each population. Immunity was higher on P-biased than C-biased diets and on low- versus high-nutrition diets, although the latter was most likely driven by compensatory feeding. These patterns persisted in populations switched to their ancestral diet, indicating genetic divergence. Crickets evolving on C-biased diets had lower immunity than the baseline, whereas their P-biased counterparts had similar or higher immunity than the baseline, indicating that populations evolved with dietary manipulation. Although females exhibited superior immunity for all assays, the sexes showed similar immune changes across diets. Our work highlights the important role that macronutrient intake plays in the evolution of immunity in the sexes

Mate choice

Much progress has been made over the last 30 years showing the complexity of female mate choice. There is now a better understanding of why females choose certain males over others, as well as the various mechanisms used to make mate choice decisions. It is also known that female mate choice can exert significant sexual selection on male sexual traits and that there is likely to be a strong genetic basis to mate choice, as well as significant positive genetic covariance between mate choice and the expression of the preferred sexual trait. However, female mate choice does not always drive the evolutionary divergence of male sexual traits in a predictable way, and the role of female mate choice in facilitating reproductive isolation and speciation is likely to be even more complex. More research on mate choice in insects is still needed and this chapter outlines some future directions

Allowing nature to be nurture : a comment on Bailey et al.

In their recent review, Bailey et al. (2017) make the compelling case that indirect genetic effects (IGEs) should be more widely incorporated into behavioral ecology research. IGEs occur whenever the trait of one individual is affected by the genotype of another “interacting” individual, usually via one or more “social cues.” IGEs create an additional source of heritable variation that can influence an individual’s trait expression above and beyond any direct contributions of its genotype (direct genetic effect [DGE]) and the environment (Lynch and Walsh 1998). When conspecifics interact, as is the case for behavioral interactions, they make up part of an individual’s “social environment” and because these interacting partners are themselves genetically variable, additional heritable variation can be generated. So why does this matter? A key outcome of IGEs is that traits affected by them can evolve not only due to direct genetic variation but also due to evolution of the social environment itself (Wolf et al. 1998)

Genotype-by-Environment Interactions and Sexual Selection

Much of the early history of evolutionary genetics was focused on understanding the relative contribution of genes and the environment to observed levels of phenotypic variation. Chief in this pursuit was Ronald A. Fisher who, amongst his many achievements, developed a statistical framework for partitioning these sources of phenotypic variance in a population. Underlying this framework was the idea that genetic and environmental sources of phenotypic variance in a population could be summed as long as they act independently, providing a simple method to statistically partition the relative effects of these sources of variation in phenotype. This logic is easy to follow if (as Fisher believed) the environment has negligible effects on phenotype and is distributed at random across individuals (and genotypes) in the population. Other researchers at the time (led most notably by Lancelot T. Hogben), however, argued that this framework under-estimated the importance of the environment and also missed a third and important source of phenotypic variation: that which arises from the combination of a particular genetic constitution with a particular kind of environment. Nowadays, we refer to this differential response of genotypes to environmental variation as genotype-by-environment interactions (GEIs) and know that this source of phenotypic variance is almost ubiquitous in most animal and plant populations. Unfortunately, most researchers in the early part of the twentieth century viewed GEIs as an annoying departure from Fisher's additive framework. This view was particularly evident in agricultural genetics where the presence of GEIs often meant that a good genotype (or crop variety) in one environment may perform poorly in another environment. In such instances, the predictive power of genotypes across environments is greatly reduced, which has obvious consequences for the efficiency of selective breeding programs. It was not until the mid-1980s, however, that the explicit role of GEIs in the evolutionary process was considered. GEIs are now known to play a key role in a number of different evolutionary processes including the maintenance of genetic variation, driving population divergence and speciation, as well as directing the evolutionary response of phenotypes to changing environments

Multivariate quantitative genetics

Selection targets multiple phenotypic traits simultaneously and results in evolutionary change that is governed by the pattern of genetic (co)variation that underlies these traits. Consequently, the genetic variance-covariance matrix (.G), which summarizes the pattern of independent and shared genetic (co)variation across traits, is a central parameter in understanding multivariate evolution. Here we discuss the central role that G plays in understanding multivariate evolution.. We use an empirical example on life-history traits in the Indian meal moth (.Plodia interpunctella) to illustrate how G can constrain phenotypic evolution. We conclude with some of the limitations of using G to understand multivariate phenotypic evolution

The evolution of parental care in the onthophagine dung beetles

There are a few areas of evolutionary biology that have progressed as rapidly as our understanding of the diversity that exists in animal mating systems (Shuster & Wade, 2003). Fundamental to this progress has been our growing appreciation of parental care, as many of the most striking differences in the reproductive behaviour of males and females are intimately linked to their involvement in the care of their young (Clutton-Brock, 1991). Sex differences in parental care play a central role in determining the intensity of sexual selection (Trivers, 1972), which, in turn, is responsible for the evolution of morphology (e.g. Hunt & Simmons, 2000), behaviour (e.g. Radford & Ridley, 2006) and physiology (e.g. Trumbo, 1997)

Evidence for strong intralocus sexual conflict in the Indian meal moth, Plodia interpunctella

Males and females share a genome and express many shared phenotypic traits, which are often selected in opposite directions. This generates intralocus sexual conflict that may constrain trait evolution by preventing the sexes from reaching their optimal phenotype. Furthermore, if present across multiple loci, intralocus sexual conflict can result in a gender load that may diminish the benefits of sexual selection and help maintain genetic variation for fitness. Despite the importance of intralocus sexual conflict, surprisingly few empirical studies conclusively demonstrate its operation. We show that the pattern of multivariate selection acting on three sexually dimorphic life-history traits (development time, body size, and longevity) in the Indian meal moth, Plodia interpunctella, is opposing for the sexes. Moreover, we combined our estimates of selection with the additive genetic variance-covariance matrix (G) to predict the evolutionary response of the life-history traits in the sexes and showed that the angle between the vector of responses and the vector of sexually antagonistic selection was almost orthogonal at 84.70°. Thus, G biases the predicted response of life-history traits in the sexes away from the direction of sexually antagonistic selection, confirming the presence of strong intralocus sexual conflict in this species. Despite this, sexual dimorphism has evolved in all of the life-history traits examined suggesting that mechanism(s) have evolved to resolve this conflict and allow the sexes to reach their life-history optima. We argue that intralocus sexual conflict is likely to play an important role in the evolution of divergent life-history strategies between the sexes in this species