Inbreeding,energy use and condition

In energetic terms, fitness may be seen to be dependent on successful allocation of energy between life‐history traits. In addition, fitness will be constrained by the energy allocation ability, which has also been defined as condition. We suggest here that the allocation ability, estimated as the difference between total energy budget and maintenance metabolism, may be used as a measure of condition. We studied this possibility by measuring the resting metabolic rate and metabolism during forced exercise in Gryllodes sigillatus crickets. To verify that these metabolic traits are closely related to fitness, we experimentally manipulated the degree of inbreeding of individuals belonging to the same pedigree, hence enabling analysis of both inbreeding depression and heritability of traits. We found that inbreeding increased maintenance metabolism, whereas total energy budget was rather insensitive to inbreeding. Despite this, inbreeding led to decreased allocation ability. Overall, metabolic traits exhibited strong inbreeding depression and rather low heritabilities, a pattern that is typical of traits under strong selection. However, traditionally used condition indices were not affected by inbreeding and did not covary with metabolic traits. Moreover, in contrast to the common, but largely untested, tenet, it seems that high resting metabolic rate is indicative of low rather than high quality.     

Inbreeding depression in the effects of body mass on energy use

Large organisms have higher metabolic rates than small organisms but, if we compare their relative metabolic rates (i.e. per gram of tissue), this relationship is very often reversed. The pervasiveness of this phenomenon, called metabolic scaling, has attracted several theoretical explanations, and also produced lingering debate over whether metabolic scaling is a physically constrained and universally constant phenomenon or a more variable and evolutionarily malleable trait. To bring novel insights to this debate, we manipulated male Gryllodes sigillatus crickets' coefficients of inbreeding to determine whether metabolic scaling is sensitive to the manipulation of genetic quality. Because inbreeding depression is inversely related to past selection, our results indicate that selection has favoured an overall lower metabolic rate and a less steep slope of metabolic scaling. Altered metabolic scaling as a result of inbreeding was found to be caused by increased variation in metabolic rate, suggesting the existence of balancing selection towards intermediate metabolic rates. Although we found effects of inbreeding on metabolic scaling, much of the relationship between body mass and metabolic rate remained unexplained, leaving plenty of room for speculation concerning the fixed constraints that might affect evolutionary trajectories. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 309–317.     

Testosterone, immunocompetence, and honest sexual signaling in male red grouse

The expression of sexual ornaments has been suggested to reliablyindicate individual quality, such as the ability to cope withparasites and diseases. The Immunocompetence Handicap Hypothesis(IHH) states that testosterone-dependent ornaments honestlysignal such quality because of physiological costs associatedwith testosterone, such as impaired immune function. We testedpredictions of the IHH both correlatively and experimentallyin red grouse Lagopus lagopus scoticus. Male grouse exhibitsupra-orbital red combs whose size is testosterone-dependent.We found that comb size was not correlated to infection intensityby two parasites (coccidia and the nematode Trichostrongylustenuis), but it was significantly positively correlated withcondition and T-cell-mediated immunity (the ability to mounta primary inflammatory response). We manipulated testosteroneby means of implants and re-caught males after a month to investigatethe effects on comb size, condition, immunity, and parasiteload. Males implanted with testosterone had increased comb size,lost more condition, and had lower T-cell-mediated immunitythan control males. Increased testosterone also resulted ina significant increase in coccidia infection intensity but hadno effect on T. tenuis burden. The results are consistent withpredictions of the IHH and suggest that comb size honestly indicatesimmunocompetence and males' ability to cope with certain parasites.Females could thus benefit from choosing mates based on theexpression of this sexual trait.     

Inbreeding,inbreeding depression and extinction

Inbreeding is unavoidable in small, isolated populations and can cause substantial fitness reductions compared to outbred populations. This loss of fitness has been predicted to elevate extinction risk giving it substantial conservation significance. Inbreeding may result in reduced fitness for two reasons: an increased expression of deleterious recessive alleles (partial dominance hypothesis) or the loss of favourable heterozygote combinations (overdominance hypothesis). Because both these sources of inbreeding depression are dependent upon dominance variance, inbreeding depression is predicted to be greater in life history traits than in morphological traits. In this study we used replicate inbred and control lines of Drosophila simulans to address three questions:1) is inbreeding depression greater in life history than morphological traits? 2) which of the two hypotheses is the major underlying cause of inbreeding depression? 3) does inbreeding elevate population extinction risk? We found that inbreeding depression was significantly greater in life history traits compared to morphological traits, but were unable to find unequivocal support for either the overdominance or partial dominance hypotheses as the genetic basis of inbreeding depression. As predicted, inbred lines had a significantly greater extinction risk.     

Parental attachment,drug use,and facultative sexual strategies

Abstract

It is often asserted that sexual promiscuity and drug abuse appears to share a common etiology in poor parental attachment. This study explores this claim empirically among 480 college students. Other variables—religiosity, masculinity/femininity, sex, age, and physical appearance—that may enhance or reduce the incidence of promiscuity and drug use were included in multivariate analyses. Parental attachment was significantly related to both variables, and the combination of poor parental attachment and drug use was a strong predictor of promiscuity for both males and females. In multivariate analyses, religiosity was the most important predictor of promiscuity for males, and attachment was the most important for females. The findings are examined guided by the three desiderata commonly accepted as relevant to biosocial attachment theory.     

Inbreeding affects sexual signalling in males but not females of Tenebrio molitor

In many species of animals, individuals advertise their quality with sexual signals to obtain mates. Chemical signals such as volatile pheromones are species specific, and their primary purpose is to influence mate choice by carrying information about the phenotypic and genetic quality of the sender. The deleterious effects of consanguineous mating on individual quality are generally known, whereas the effect of inbreeding on sexual signalling is poorly understood. Here, we tested whether inbreeding reduces the attractiveness of sexual signalling in the mealworm beetle, Tenebrio molitor, by testing the preferences for odours of inbred and outbred (control) individuals of the opposite sex. Females were more attracted to the odours produced by outbred males than the odours produced by inbred males, suggesting that inbreeding reduces the attractiveness of male sexual signalling. However, we did not find any difference between the attractiveness of inbred and outbred female odours, which may indicate that the quality of females is either irrelevant for T. molitor males or quality is not revealed through female odours.     

Inbreeding,maternal care and genomic imprinting

Inactivation of expression of the paternal allele at two maternally silent imprinted loci has recently been reported to diminish the quality of care that female mice lavish on their offspring. This suggests that there can be disagreement between the maternally and paternally derived genomes of mothers over how much care for offspring is appropriate, with the paternally derived genome favoring greater care. The reason for such disagreement is not obvious because the maternally and paternally derived alleles at a locus have equal probabilities of being transmitted to each of the mother's ova and, therefore, would appear to have equal interests in a mother's offspring. However, if a female mates with a related male, her two alleles may have different probabilities of being present in the sperm that fertilize her ova. Natural selection can favor silencing of the maternally derived allele at a locus that enhances the quality of maternal care if the average patrilineal relatedness between a female and her mates decreases more rapidly than the average matrilineal relatedness. Just such an asymmetrical decrease in relatedness over time would be expected in a structured population in which patrilineal inbreeding is more common than matrilineal inbreeding.     

Inbreeding,kin selection,and primate social evolution

In this paper I argue (a) that the study of kin selection may be facilitated by looking for influences of inbreeding, which is an important aspect of a population's genetic structure; (b) that in nonhuman primates the level of inbreeding will be largely a function of the rate of migration by individuals, usually only of one sex, between social units or troops; (c) that many primate species live in relatively outbred groups, and that their social structure reflects this; and (d) that extensive social contrasts between bonnet and pigtail macaques reflect evolution by kin selection under different levels of inbreeding.     

Inbreeding, biological and mental variations in France

Coefficients of inbreeding, known for most French départements, correlate not only with body-height, as previously shown, but also with other anthropometrical, physiological, biochemical and mental characteristics. It does not appear that these correlations were primarily determined by differences in socio-economic or cultural levels.     

Inbreeding and genetic disease in Sottunga, Finland

The contribution of inbreeding to the prevalence of recessive genetic diseases in the Aland Island parish of Sottunga is investigated. Genealogical data for 3,030 individuals spanning up to 15 generations were used to estimate inbreeding. This small island community shows a low average inbreeding value of .0031 for the period 1725-1975. A cohort analysis shows that inbreeding increased from 1750 to 1900, when maximum inbreeding for those born in Sottunga reached .0057. A sharp decline in inbreeding occurred thereafter. Individuals with island-born parents made the largest contributions to inbreeding in all time periods compared to those with one or two migrant parents. These trends are consistent with changing migration patterns and isolate breakdown in Aland since 1900. An analysis of pedigree development demonstrates that remote consanguinity contributed more to inbreeding through time than close consanguinity. Both the number of common ancestors and the number of paths of relationship between spouses increased dramatically through time, the latter at a much faster rate. The contribution to average inbreeding per path, however, diminished rapidly through time. This analysis indicates that inbreeding does not account for the high incidence of autosomal recessive disorders, such as tapetoretinal disease, found in the parish.