Extra-pair paternity explains cooperation in a bird species.

In many social animals, females mate with multiple males, but the adaptive value of female extra-pair mating is not fully understood. Here, we tested whether male pied flycatchers (Ficedula hypoleuca) engaging in extra-pair copulations with neighboring females were more likely to assist their neighbors in antipredator defense. We found that extra-pair sires joined predator-mobbing more often, approached predators more closely, and attacked predators more aggressively than males without extra-pair offspring in the neighboring nest. Extra-pair mating may incentivize males to assist in nest defense because of the benefits that this cooperative behavior has on their total offspring production. For females, this mating strategy may help recruit more males to join in antipredator defense, offering better protection and ultimately improving reproductive success. Our results suggest a simple mechanism by which extra-pair mating can improve reproductive success in breeding birds. In summary, males siring extra-pair offspring in neighboring nests assist neighbors in antipredator defense more often than males without extra-pair offspring.

Ecological traps: evidence of a fitness cost in a cavity-nesting bird.

Habitat quality has direct effects on the evolutionary fitness of breeding organisms, which is why it is believed that animals tend to have an evolved preference for the best possible habitats. However, some animals may mistakenly choose to reproduce in habitats that decrease their fitness, resulting in 'ecological traps'. In this study, we tested whether great tits (Parus major) attracted to areas affected by outbreaks of the great web-spinning sawfly (Acantholyda posticalis) had fitness detriments characteristic of ecological traps. Sawfly larvae consume pine needles, which decreases resource availability for birds co-habiting the forest. Using artificial nesting sites, we found that great tits inhabiting areas of sawfly outbreaks had similar clutch sizes as tits breeding in healthy forest patches; however, the fledgling number was significantly lower, and fledgling condition was worse in the damaged forests. While moth larvae are the most important food for bird nestlings, the forest patches damaged by sawflies had lower larval biomass. Although most ecological traps occur in environments altered by humans, this study shows that pest insects can lower habitat quality, forming ecological traps. Our results indicate that attracting cavity-nesting birds should be done with caution because it may negatively impact birds' nutritional status and reproductive fitness.

A Life History Approach to the Female Sexual Orientation Spectrum: Evolution, Development, Causal Mechanisms, and Health.

Women's capacity for sexual fluidity is at least as interesting a phenomenon from the point of view of evolutionary biology and behavioral endocrinology as exclusively homosexual orientation. Evolutionary hypotheses for female nonheterosexuality have failed to fully account for the existence of these different categories of nonheterosexual women, while also overlooking broader data on the causal mechanisms, physiology, ontogeny, and phylogeny of female nonheterosexuality. We review the evolutionary-developmental origins of various phenotypes in the female sexual orientation spectrum using the synergistic approach of Tinbergen's four questions. We also present femme-specific and butch-specific hypotheses at proximate and ultimate levels of analysis. This review article indicates that various nonheterosexual female phenotypes emerge from and contribute to hormonally mediated fast life history strategies. Life history theory provides a biobehavioral explanatory framework for nonheterosexual women's masculinized body morphology, psychological dispositions, and their elevated likelihood of experiencing violence, substance use, obesity, teenage pregnancy, and lower general health. This pattern of life outcomes can create a feedback loop of environmental unpredictability and harshness which destabilizes intrauterine hormonal conditions in mothers, leading to a greater likelihood of fast life history strategies, global health problems, and nonheterosexual preferences in female offspring. We further explore the potential of female nonheterosexuality to function as an alloparental buffer that enables masculinizing alleles to execute their characteristic fast life history strategies as they appear in the female and the male phenotype. Synthesizing life history theory with the female sexual orientation spectrum enriches existing scientific knowledge on the evolutionary-developmental mechanisms of human sex differences.

A head start for life history development? Family income mediates associations between height and immune response in men.

OBJECTIVES: Male height and health affect a diverse range of social and economic outcomes such as competition for resources and mates. Life history theory predicts that limited availability of bioenergetic resources curbs the development of central life history functions such as somatic growth, immunity, and investment in offspring. Although genetic factors are important determinants of height, other factors such as income level may affect the incidence of infections during ontogeny, thus having indirect effects on somatic growth. We tested whether growing up in families with a higher income positively affects height and immune function. MATERIALS AND METHODS: Seventy-three young Latvian men from various socioeconomic backgrounds were given a hepatitis B vaccine. Blood samples were subsequently collected to measure the antibodies produced in response to the vaccination. Tweedie compound Poisson generalized linear models were used to examine relationships between height, family income, and antibody titers. RESULTS: Both height and family income positively correlated with the strength of men's immune response. However, when testing for the simultaneous effects of height and income on antibody titers, the statistical models showed that height affected antibody levels indirectly because income level mediated variance in height. DISCUSSION: The results of this study show that the relationships between height and immune function in young men are more complex than previously thought. Associations between taller stature of men and the robustness of their immune response are indirect because resource availability affects both somatic growth and the development of the immune system.

England first, America second: The ecological predictors of life history and innovation.

We present data from 122 nations showing that Baumard's argument on the ecological predictors of life history strategies and innovation is incomplete. Our analyses indicate that wealth, parasite stress, and cold climate impose orthogonal effects on life histories, innovation, and industrialization. Baumard also overlooks the historical exploitation of other nations which significantly enlarged the "pooled energy budget" available to England.

Depression subtyping based on evolutionary psychiatry: Proximate mechanisms and ultimate functions.

Major depressive disorder constitutes one of the leading causes of disability worldwide. However, it is not a unitary disease-it is a heterogeneous syndrome, with patients differing remarkably in symptom profile, pathophysiology and treatment responsiveness. Previous attempts to subtype major depressive disorder have showed limited clinical applicability. We present a classification of major depressive disorder episodes based on the proximate mechanisms that led to the original mood change that caused the depressive episode. We identify discrete depression subtypes that are induced by: 1) infection, 2) long-term stress, 3) loneliness, 4) traumatic experience, 5) hierarchy conflict, 6) grief, 7) romantic rejection, 8) postpartum events, 9) the season, 10) chemicals, 11) somatic diseases and 12) starvation. We further examine the ultimate functions of these subtypes and show that not all types of mood changes that trigger depression are adaptive. Instead, some are clearly maladaptive and some are byproducts of other adaptations. In modern societies, low mood after adverse life events may turn into a pathological depressive state. Modern lifestyle increases susceptibility to inflammatory dysregulation and chronic stress, both of which increase the amount of proinflammatory cytokines in peripheral blood, leading to low mood and sickness behaviour. Proinflammatory cytokines may aggravate the previously adaptive short-term mood changes to a chronic maladaptive depressive state by preventing the normalization of mood after adverse life events. Subtyping depression enables an effective and intelligent long-term treatment of patients in each subtype by treating the underlying causes of depression.

Metabolic rate associates with, but does not generate covariation between, behaviours in western stutter-trilling crickets, Gryllus integer.

The causes and consequences of among-individual variation and covariation in behaviours are of substantial interest to behavioural ecology, but the proximate mechanisms underpinning this (co)variation are still unclear. Previous research suggests metabolic rate as a potential proximate mechanism to explain behavioural covariation. We measured the resting metabolic rate (RMR), boldness and exploration in western stutter-trilling crickets, Gryllus integer, selected differentially for short and fast development over two generations. After applying mixed-effects models to reveal the sign of the covariation, we applied structural equation models to an individual-level covariance matrix to examine whether the RMR generates covariation between the measured behaviours. All traits showed among-individual variation and covariation: RMR and boldness were positively correlated, RMR and exploration were negatively correlated, and boldness and exploration were negatively correlated. However, the RMR was not a causal factor generating covariation between boldness and exploration. Instead, the covariation between all three traits was explained by another, unmeasured mechanism. The selection lines differed from each other in all measured traits and significantly affected the covariance matrix structure between the traits, suggesting that there is a genetic component in the trait integration. Our results emphasize that interpretations made solely from the correlation matrix might be misleading.

Microbiome symbionts and diet diversity incur costs on the immune system of insect larvae.

Communities of symbiotic microorganisms that colonize the gastrointestinal tract play an important role in food digestion and protection against opportunistic microbes. Diet diversity increases the number of symbionts in the intestines, a benefit that is considered to impose no cost for the host organism. However, less is known about the possible immunological investments that hosts have to make in order to control the infections caused by symbiont populations that increase because of diet diversity. Using taxonomical composition analysis of the 16S rRNA V3 region, we show that enterococci are the dominating group of bacteria in the midgut of the larvae of the greater wax moth (Galleria mellonella). We found that the number of colony-forming units of enterococci and expressions of certain immunity-related antimicrobial peptide (AMP) genes such as Gallerimycin, Gloverin, 6-tox, Cecropin-D and Galiomicin increased in response to a more diverse diet, which in turn decreased the encapsulation response of the larvae. Treatment with antibiotics significantly lowered the expression of all AMP genes. Diet and antibiotic treatment interaction did not affect the expression of Gloverin and Galiomicin AMP genes, but significantly influenced the expression of Gallerimycin, 6-tox and Cecropin-D Taken together, our results suggest that diet diversity influences microbiome diversity and AMP gene expression, ultimately affecting an organism's capacity to mount an immune response. Elevated basal levels of immunity-related genes (Gloverin and Galiomicin) might act as a prophylactic against opportunistic infections and as a mechanism that controls the gut symbionts. This would indicate that a diverse diet imposes higher immunity costs on organisms.

Habitat quality affects stress responses and survival in a bird wintering under extremely low ambient temperatures.

Animals normally respond to stressful environmental stimuli by releasing glucocorticoid hormones. We investigated whether baseline corticosterone (CORT), handling-induced corticosterone concentration(s), and body condition indices of members of willow tit (Poecile montanus) groups differed while wintering in old growth forests and managed young forests in mild weather conditions and during cold spells. Willow tits spend the winter season in non-kin groups in which dominant individuals typically claim their priority to access resources, while subordinate individuals may experience greater levels of stress and higher mortality, especially during cold spells. We captured birds to measure baseline CORT and levels of handling-induced CORT secretion after 20 min of capture. Willow tits in the young forests had higher baseline CORT and a smaller increase in CORT in response to capture than individuals in the old forests. Baseline CORT was higher in females and juvenile birds compared to adult males, whereas handling-induced CORT secretion did not differ between birds of different ages. During cold spells, baseline CORT of willow tits increased and handling-induced CORT secretion decreased, especially in birds in young forests. Willow tits' survival was higher in the old forests, with dominant individuals surviving better than subordinates. Our results show that changes in CORT secretion reflect responses to habitat quality and climate harshness, indicating young managed coniferous forests as a suboptimal habitat for the willow tit.

A dark cuticle allows higher investment in immunity, longevity and fecundity in a beetle upon a simulated parasite attack.

Cuticle melanism in insects is linked to a number of life history traits: a positive relationship is hypothesized between melanism, immune function, fecundity and lifespan. However, it is not clear how activation of the immune system affects trade-offs between life history traits in female mealworm beetles (Tenebrio molitor) differing in cuticle melanization. The females with tan, brown and black cuticles examined in the present study did not differ in the intensity of encapsulation response, fecundity and longevity when their immune system was not activated. However, we found that immune activation and cuticle melanization have a significant effect on life history traits. Offspring number and lifespan decreased in females with tan and brown cuticles, while the fecundity and lifespan of black females were not affected. Importantly, we inserted the implants again and found a significant decrease in the strength of encapsulation response in females with tan and brown cuticles. In contrast, black females increased melanotic reactions against the nylon implant, suggesting immunological priming. The results show that cuticle melanization plays an important adaptive role under the risk of being infected, while the lack of these benefits before the insertion of nylon monofilaments suggests that there are costs associated with an activated immunity system.

The effect of yin yoga intervention on state and trait anxiety during the COVID-19 pandemic.

Introduction: Although some findings indicate that yoga can reduce stress and anxiety, many studies present mixed results. The potential of yoga interventions to alleviate anxiety, including the mechanisms and boundary conditions by which it does so, is an under-researched topic. Anxiety is often divided into "state anxiety" and "trait anxiety," the former being a temporary reaction to stressful events, while the latter is a more stable personality feature that responds to adverse situations or perceived threats. Materials and methods: This study investigates whether a yin yoga intervention delivered online reduces state anxiety immediately after each yoga session and whether the anxiety levels are significantly lower at the end of the 10-week yoga intervention than at the beginning of the study. We also predicted no effect of yin yoga intervention on trait anxiety. The study was conducted during the COVID-19 pandemic when participants (N = 48 Latvian women) experienced heightened anxiety levels. Results: This study shows that a ten-week online yin yoga intervention significantly reduced state anxiety in the intervention group compared with the control group. State anxiety levels also significantly decreased after each yin yoga session, providing more support for the anxiety-reducing effect of yin yoga. In contrast, yoga participation did not cause differences in trait anxiety between the control and intervention groups, even though trait anxiety decreased in the intervention group and increased in the control group over the study period. Conclusion: The positive effects of yin yoga on state anxiety indicate the potential of yin yoga intervention as a first-line treatment to control and reduce state anxiety, with possible additional effects on trait anxiety.