Sibling resemblance in natal dispersal distance and direction in the Ortolan Bunting Emberiza hortulana

Natal dispersal distance and direction determine the likelihood that siblings will settle close together and hence the risk of inbreeding. Several studies have shown a sibling resemblance in dispersal distance, but few studies have analysed sibling resemblance in dispersal direction or the distance between siblings after dispersal at the landscape level. I studied the entire Norwegian population of Ortolan Buntings Emberiza hortulana, which is patchily distributed in an area covering c. 500 km². Males and females did not differ in dispersal distance (overall median 3.7 km), but directions were different. Natal dispersal distances and directions were positively related within sibling pairs, but comparisons with control individuals suggested that any effects were due to spatial effects of configuration of habitat patches in the study area. Brother–sister pairs (n = 16) were at least as similar as brother–brother pairs (n = 18). Distance between siblings after natal dispersal increased with dispersal distance, but even so, five of 35 sibling pairs settled < 1 km apart, despite dispersal distances of 8.3–9.9 km for two of these pairs. Including movements later in life, eight sibling pairs were < 1 km apart at some time (four pairs of brothers and four brother–sister pairs), and in one case a brother mated with its sister. Another case of mating between close relatives (father and daughter) involved short female natal dispersal. These data indicate that female‐biased natal dispersal and long‐distance dispersal may reduce, but do not exclude, the possibility of inbreeding.     

Intralocus sexual conflict over human height

Intralocus sexual conflict (IASC) occurs when a trait under selection in one sex constrains the other sex from achieving its sex-specific fitness optimum. Selection pressures on body size often differ between the sexes across many species, including humans: among men individuals of average height enjoy the highest reproductive success, while shorter women have the highest reproductive success. Given its high heritability, IASC over human height is likely. Using data from sibling pairs from the Wisconsin Longitudinal Study, we present evidence for IASC over height: in shorter sibling pairs (relatively) more reproductive success (number of children) was obtained through the sister than through the brother of the sibling pair. By contrast, in average height sibling pairs most reproductive success was obtained through the brother relative to the sister. In conclusion, we show that IASC over a heritable, sexually dimorphic physical trait (human height) affects Darwinian fitness in a contemporary human population.     

Child survival and its effect on mortality of siblings in Bangladesh

This study of the relationship between mortality risks of siblings born to the same mother shows that, in Bangladesh, the death of the immediately preceding sibling in its infancy has a negative influence on the survival chance of the child in question in its infancy; however, death of the preceding sibling appears to have a positive influence on the index child's survival at ages 1-5 years. Similar results are found for the survival status of the two preceding siblings. Preceding birth interval length and survival status and sex of the immediately preceding sibling are also significant predictors of child mortality between ages 1 and 5 years. Possible explanations may be that the index child faces stronger competition from its immediately preceding brother than from its immediately preceding sister, or that the index child is likely to be looked after more by its preceding sister than by its preceding brother.     

Sibling recognition in the prairie vole, Microtus ochrogaster

Since mating is seldom observed between sibling prairie voles, Microtus ochrogaster, this, behavioural discrimination was used to investigate sibling recognition in this species. Cross-fostering of 1–3-day-old pups demonstrated that unrelated pups reared together did not breed, whereas siblings reared apart bred readily when paired at weaning. When unrelated voles were paired at 14 days of age, prior to sexual maturity, significantly fewer pairs bred than when strangers were paired at 21 days of age. Separation of 21-day-old siblings for 8 days before pairing overcame incest avoidance; a 15-day separation was required for breeding by siblings that had remained together until they were 50 days old. These results indicate that sibling recognition and, consequently, incest avoidance depend on association prior to weaning.     

Kin preference behaviour is present after metamorphosis in Rana cascadae frogs

Kin recognition was investigated in newly metamorphosed Rana cascadae frogs. Previous work has shown that larvae of this species prefer to associated with siblings over non-siblings. Juvenile frogs from three clutches were reared with siblings and tested for sibling preference as larvae and at 4–12 days and 39–47 days after metamorphosis. Tadpoles and froglets of the three clutches displayed a significant preference to associate with siblings.     

Sibling composition during childhood and adult blood pressure among native Amazonians in Bolivia

Sibling configuration, including birth order, or the number, age, and sex of siblings is associated with parental resource allocation between children and is thus associated with a person's well-being. Little is known about the association between specific types of siblings and adult health outcomes. Here we test several hypotheses about sibling composition (number of older brothers, older sisters, younger sisters, younger brothers) and adult blood pressure in a foraging-farming society of native Amazonians in Bolivia (Tsimane’). We collected data in 2007 from 374 adults (16–60 years of age) from 196 households in 13 villages. Household random-effects multiple regressions were run using systolic (SBP) or diastolic blood pressure (DBP) as outcomes; covariates included the four sibling categories and control variables (e.g., sex, age, education, body mass index [BMI]). Mean SBP and DBP were 114 (SD = 14) and 66 (SD = 11) mmHg. The prevalence of hypertension was 5.08%. Having an additional younger brother bore a small (3.3–5.9%) positive association with both SBP and DBP, with the effect weakening as people aged. Having an additional younger sister was associated with a small (3.8%) increase in SBP among women, with the magnitude shrinking as people aged. In a large family, the number of younger brothers may exert an impact on an individual's blood pressure.     

The Bacon Chow study: Genetic analysis of physical growth in assessment of energy–protein malnutrition

Estimates of the prevalence of energy–protein malnutrition almost universally employ physical growth measurements. In this study we focus on this disease and the role of body size of relatives as mediators of responses in individuals to one type of nutrition intervention: supplementation of pregnant and lactating women. In this study, initiated by Dr. Bacon Chow and others in 1967, during gestation of a first infant a mother was untreated, while during the lactation of the first infant and the gestation and lactation of a second infant she was treated with either a calorie supplement or a placebo. Supplement–placebo group differences were sought in sibling and mother–child correlations in growth from birth to 30 months, in order to assess the role of heredity as a mediator of supplement effects. There were 108 pairs of siblings whose mothers had received a high-calorie–high-protein supplement as described above and 105 pairs of siblings whose mothers had received a placebo. Among the latter, sibling correlations for most measurements are statistically significant at birth, and of the same magnitude seen in previous studies (～0.5), while among supplemented siblings, birth correlations are unusually low and often insignificant. The sibling correlations in Rohrer's index (wt/L³) differed the most between groups (p < 0.01). Group differences in the sibling correlation tended to disappear over the first 2.5 years of life. Correlations between mothers and their second children in subscapular skinfold tended to be higher in the supplemented than in the placebo group, birth to 30 months. In both supplement groups mother–second child correlations for body weight were higher than mother–first child correlations, suggesting the occurrence of secular changes in the environment unconnected with the treatment. The results suggest that: (1) genetic analysis of components of anthropometric variation may be a more sensitive method than the more conventional comparison of group means in detecting supplement effects; and (2) infant relative weight (Rohrer index), particularly the addition of subcutaneous fat, may be more affected by maternal supplementation than growth in weight or length alone.     

Towards a genetic theory for the evolution of the sex ratio. III. Parental and sibling control of brood investment ratio under partial sib-mating

Models of sex ratio evolution under partial sib-mating are investigated in haplodiploids and diploids. In the cases of parental and sibling control of the brood investment ratio between the sexes in diploids, we find that the “unbeatable” investment ratio obtained by W. D. Hamilton (Science156, 477–488) for his local mate competition model corresponds in our inbreeding models to a weak form ESS (evolutionary stable strategy) fixation state and also to the population investment ratio at certain internal equilibria of our models. For haplodiploids, “strong form ESS” values exist under inbreeding in models involving father and sister control. Under brother and mother control, however, the ESS derived from local mate competition models is unstable in our inbreeding models to the introduction of any other investment ratio. We stress important qualitative differences between models involving local mate competition and inbreeding.     

Molecular perspective on the American transisthmian species of Macrobrachium (Caridea,Palaemonidae)

The closure of the Isthmus of Panama (about 3.1 million years ago) separated previously continuous populations and created two groups of extant species, which live now in the Pacific and Atlantic drainage systems. This relatively recent event was a trigger to diversification of various species in the Neotropics, nonetheless there are exemplars that do not show sufficient morphologic variability to separate them by traditional morphological tools. About 60 years ago, some freshwater decapod species with high morphological similarity were separate by previous researchers, based on geographical distribution, in Pacific and Atlantic and considered as “sister species”. However, the complete isolation of these prawns by this geographical barrier is questionable, and it has generated doubts about the status of the following transisthmian pairs of sibling species: Macrobrachium occidentale × Macrobrachium heterochirus, Macrobrachium americanum × Macrobrachium carcinus, Macrobrachium digueti × Macrobrachium olfersii, Macrobrachium hancocki × Macrobrachium crenulatum, Macrobrachium tenellum × Macrobrachium acanthurus and Macrobrachium panamense × Macrobrachium amazonicum. Here we evaluated the relation among these pairs of sibling species in a molecular phylogenetic context. We generated 95 new sequences: 26 sequences of 16S rDNA, 25 of COI mtDNA and 44 of 18S nDNA. In total, 181 sequences were analyzed by maximum likelihood phylogenetic method, including 12 Macrobrachium transisthmian species, as well as seven other American Macrobrachium species, and two other palaemonids. Our analysis corroborated the morphological proximity of the sibling species. Despite the high degree of morphological similarities and considerable genetic diversification encountered among the transisthmian sister species, our data support the conclusion that all species included in sibling groups studied herein are valid taxonomic entities, but not all pairs of siblings form natural groups.     

Will granny save me? Birth status,survival, and the role of grandmothers in historical Finland

Grandmothers play a crucial role in families enhancing grandchild wellbeing and survival but their effects can be context-dependent, and the children born in poor conditions are most likely to benefit from the investments made by helping grandmothers. In this study, we examined, for the first time, whether grandmothers' presence modified associations between adverse birth status and survival up to 5 years of age. In detail, we verified, whether (i) firstborns, (ii) twins, (iii) children born within 24 months after their sibling, and (iv) children followed by short interval (i.e. their younger sibling was born within 24 months) survived better when either their maternal, paternal, or both grandmothers were present. Moreover, we evaluated whether illegitimate children survived better when the maternal grandmother was present. We used an extensive and largely pre-industrial demographic dataset collected from parish population registers kept by the Lutheran Church of Finland from years 1730–1895. We show that although grandmother presence cannot mitigate adverse effects of many poorer birth conditions, grandchildren whose next sibling was born after a short interval survived better when the maternal grandmother was present. Taken together, these findings highlight an important role of grandmothers in compensating the mother's investment in the new baby, thus enabling overall faster successful reproductive rate of mothers. Whilst the opportunity for grandmothers to mitigate the risks of adverse birth statuses is limited, this study does show - through the beneficial effect on survival for those with a short subsequent birth interval - that grandmothers can increase their daughters' and their own reproductive success.     

The Westermarck effect revisited: a psychophysiological study of sibling incest aversion in young female adults

Research on human inbreeding avoidance has uncovered at least two central cues to the detection of siblings: witnessing an infant being taken care of by one's mother (i.e. maternal perinatal association) and growing up in close proximity to a child (the so-called Westermarck effect). Both cues have been supported by fieldwork in populations under specific cultural conditions, and by survey research mainly in student populations. Both types of research have relied often on self-reporting. Unfortunately, this method is frequently colored by ceiling effects and notions of social desirability. In order to circumvent this problem, we explored a complementary method for investigating incest aversion that involved measuring psychophysiological responses during an imagery task. As such, we analyzed data on 63 heterosexual female students who viewed pictures of sexual and non-sexual activities while imagining performing these activities with either their partner or their brother. In female subjects with only (one or more) older brothers—a proxy for lacking maternal perinatal association with an opposite-sex sibling—the duration of coresidence with brother(s) predicted activity in the mm. levator labii superioris and alaeque nasi, facial muscles that are highly active when a subject expresses facial disgust. The strength of these responses was also predicted by the frequency of having bathed and shared a bedroom with a brother in early childhood; two activities that may serve as additional cues for relatedness as it can be expected that they are typically performed with genetically related children. As a result, the psychophysiological approach not only complements the use of self-reports in recent research on incest aversion, but also has the potential to fine-tune well-established cues for sibling detection, or to uncover additional ones.     

Parental substance misuse and reproductive timing in offspring: A genetically informed study

Parents with substance misuse provide their children with a potentially risky rearing environment. According to the evolutionary life history theory, such environments steer individuals towards faster reproductive strategy. However, parents providing their children with hazardous environments may also pass on genes associated with early parenthood. In register data on individuals born in Sweden 1973–1993 (N = 2,176,128), the hazard ratio of entering parenthood by age 25 was 1.70 (95% CI 1.69–1.72) and 1.85 (1.82–1.89) among offspring of fathers and mothers with substance misuse, respectively, compared to others. In analyses using an offspring-of-siblings design in three types of parental sibling pairs (half siblings, full siblings and dizygotic twins, and monozygotic twins) increasingly controlling for genetic confounding, associations between parental substance misuse and offspring's early reproduction gradually attenuated. Our results suggest that the association between parental substance misuse and earlier parenthood in offspring is at least partly genetically confounded. Life history theory should be further tested with genetically informative research designs.     

Sex of preceding sibling and anthropometrics of subsequent offspring at birth and in young adulthood: A population‐based study in Sweden

In many mammal species with sexual dimorphism producing sons is energetically more demanding to the mother than producing daughters. Although some studies in humans have suggested that offspring born after a brother have a smaller birth weight and adult height when compared with those born after a sister, little is known about this intergenerational cost of producing sons. We aimed to study whether the sex of preceding sibling is associated with anthropometrics of the subsequent child at birth and in young adulthood. This population‐based study was carried out on two data sets derived from the Swedish registers. Information on birth weight and length was obtained for 752,723 children of both sexes. Adult weight, height and muscle strength were available for 506,326 men. Multiple linear regression analyses showed that boys and girls born after a brother were, respectively, 18 and 9 g lighter and 0.08 and 0.03 cm (P < 0.001) shorter at birth than those born after a sister. Adjustment for gestational age decreased the magnitude of the associations [10 g and 0.04 cm (P < 0.001) in men and nonsignificant estimates in women], suggesting that part of the lower mean birth weight and length of individuals born after a brother was due to a shorter gestation. In young adulthood, men with a preceding brother showed 0.16 kg more in weight, 0.3% higher body mass index (P < 0.001) and a trend towards reduced height and muscle strength. Our results suggest that even though the sex of the previous child is associated with the anthropometrics of the subsequent child, the effect sizes are very small questioning whether this mechanism has adaptive value in contemporary humans. Am J Phys Anthropol 154:471–478, 2014. © 2014 Wiley Periodicals, Inc.     

Gender,family configuration,and the effect of family background on educational attainment

Abstract

A comprehensive model of family influences on educational resemblance of siblings expands the traditional sibling pair model to a full sibship model in order to investigate how gender, gender composition of sibships, and a measure of ordinal position moderate the effect of social origins on educational attainments of siblings. One common family factor is sufficient to explain the variation of educational attainment among brothers and sisters. Although effects of social origin variables on brothers are larger than on sisters, the relative effects of measured social origins are virtually the same among sisters and brothers. The disparity between educational attainments of brothers and sisters persists across sex composition and family size. Ordinal position does not alter the effects of social origins on educational attainment nor does it directly affect educational attainment. Father's and mother's education are equally important for all siblings regardless of birth order, gender composition, and family size.     

Familial Carotid Body Tumors In Patients With Sdhd Mutations: A Case Series

ObjectiveTo describe a family with hereditary paraganglioma due to a disease-causing mutation in the SDHD gene.MethodsWe present the clinical findings, diagnostic test results, treatment, and genetic test results in a family with hereditary paraganglioma.ResultsThree siblings with bilateral carotid body tumors presented at different time points and with varied clinical presentations. While the proband, a 20-year-old man, was not hypertensive and had normal urinary metanephrine and normetanephrine levels, his sister and brother had a more severe clinical picture, with hypertension in both and elevated normetanephrine levels in his brother (his brother had pheochromocytoma and 2 intra-abdominal paragangliomas). Mean age at presentation was 24 years. A 4-base pair frameshift mutation, c.337-340delGACT, was detected in exon 4 of the SDHD gene in all 3 patients.ConclusionThis is the first report of the c.337340delGACT mutation being associated with hereditary paraganglioma; this report emphasizes the need to screen all at-risk first-degree relatives for the disease-causing SDHD mutation once it has been identified in an affected family member. (Endocr Pract. 2012;18:e106-e110)     

Self-grooming and sibling recognition in meadow voles,Microtus pennsylvanicus,and prairie voles,M. ochrogaster

Self-grooming in response to the odours of an opposite-sex conspecific may reflect sexual motivation on the part of the actor. We tested the hypothesis that meadow voles, Microtus pennsylvanicus, and prairie voles,M. ochrogaster , both self-groom at different rates when exposed to the odours of their siblings as compared to those of nonsiblings. This prediction was studied under the context of social memory for siblings and the effects of isolation on memory for siblings. The hypothesis explains the self-grooming responses of meadow voles isolated from their siblings for 10 days and of prairie voles isolated from their siblings for 20 days. However, 20 days of isolation for male and female meadow voles, and 30 days of isolation for male prairie voles were sufficient to induce these animals to self-groom at a similar rate to both sibling and nonsibling odours, suggesting that after isolation these animals no longer recognized their opposite-sex siblings. Female prairie voles isolated for 30 days self-groomed more in response to the odours of male nonsiblings than to those of male siblings, suggesting that female prairie voles still recognize their male siblings after isolation. This study is the first to provide empirical evidence that, in the context of sibling recognition, self-grooming behaviour is directed at unfamiliar opposite-sex conspecifics, and that the communicative function of self-grooming (sexual motivation) is associated with social memory for siblings. Differences in the self-grooming behaviour of meadow voles and prairie voles may be associated with several aspects of their life history characteristics.     

Consequences of mating with siblings and nonsiblings on the reproductive success in a leaf beetle

Choosing a suitable mating partner is crucial for the fitness of an individual, whereby mating with siblings often results in inbreeding depression. We studied consequences of mating with siblings versus nonsiblings in the mustard leaf beetle, Phaedon cochleariae (Coleoptera: Chrysomelidae), on lifetime reproductive traits. Furthermore, we analyzed whether cuticular hydrocarbon (CHC) profiles are family specific and could potentially influence the mating behavior of young adults. We hypothesized a reduced reproductive success of females mated with siblings and a more rapid mating of males with nonsiblings. The hatching rate from eggs of sibling pairs was lower compared to that of nonsibling pairs, pointing to inbreeding depression. Furthermore, the number of eggs laid by females decreased over time in both sibling and nonsibling pairs. Interestingly, the CHC profiles and the body mass differed between families. However, the beetles did not avoid siblings and accepted them as readily as nonsiblings for mating in no‐choice tests. In summary, although it had negative consequences to mate a sibling and although siblings could potentially be recognized by their CHC profiles, the beetles did not show a delayed mating with siblings. Our results indicate that P. cochleariae beetles have not developed a precopulatory mechanism to avoid inbreeding, at least under the test conditions applied here. We predict that instead a polyandrous mating system and/or postcopulatory mechanisms might have evolved in this species by which inbreeding costs can be reduced.     

3. NOTES OF THE BIRDS OF THE KRUGER NATIONAL PARK

Mundy. P. J. &; Cook. A. W. 1975. Hatching and rearing of two chicks by the Hooded Vulture. Ostrich 46:45-50

The single-egg clutches of 10 pairs of Hooded Vultures Necrosyrtes monachus were doubled by the addition of one egg to each in the breeding season of 1971/72 at Sokoto, Nigeria. Three pairs hatched both eggs and a further two pairs hatched one egg each. Only one pair raised both chicks to fledging and, apart from a depressed weight gain and tail growth of the younger “sibling”, the chicks grew at approximately the average rate for the species. The average rate was determined by following 27 normal nests in the study area. There was no evidence of aggression between the “siblings”. It was suggested that the success of one adult pair in raising two chicks was partly occasioned by the chicks' ages being only four days apart, and by the unusually rich food supply available from nearby human activities.     

An investigation of sibling recognition in Rana cascadae tadpoles

Sibling recognition was studied experimentally in tadpoles of the Cascades frog, Rana cascadae. Sibships were divided into two groups at an early developmental stage. One group was reared with siblings and the second with a mixture of siblings and non-siblings. Whe given a choice of associating with a sibling or non-sibling group, individuals reared with siblings preferred siblings. One mixed-reared group spent more time associating with unfamiliar siblings than unfamiliar nonsiblings. Tadpoles of another mixed-reared group preferred to associate with pure siblings over a mixture of siblings and non-siblings with which they were reared. When the stimulus animals were taken exclusively from the mixed-rearing tank, two mixed-reared groups showed no sibling preferences. Our results suggest that early association with non-siblings does not affect sibling recognition in this species.     

Evaluating indirect genetic effects of siblings using singletons

Estimating effects of parental and sibling genotypes (indirect genetic effects) can provide insight into how the family environment influences phenotypic variation. There is growing molecular genetic evidence for effects of parental phenotypes on their offspring (e.g. parental educational attainment), but the extent to which siblings affect each other is currently unclear. Here we used data from samples of unrelated individuals, without (singletons) and with biological full-siblings (non-singletons), to investigate and estimate sibling effects. Indirect genetic effects of siblings increase (or decrease) the covariance between genetic variation and a phenotype. It follows that differences in genetic association estimates between singletons and non-singletons could indicate indirect genetic effects of siblings if there is no heterogeneity in other sources of genetic association between singletons and non-singletons. We used UK Biobank data to estimate polygenic score (PGS) associations for height, BMI and educational attainment in self-reported singletons (N = 50,143) and non-singletons (N = 328,549). The educational attainment PGS association estimate was 12% larger (95% C.I. 3%, 21%) in the non-singleton sample than in the singleton sample, but the height and BMI PGS associations were consistent. Birth order data suggested that the difference in educational attainment PGS associations was driven by individuals with older siblings rather than firstborns. The relationship between number of siblings and educational attainment PGS associations was non-linear; PGS associations were 24% smaller in individuals with 6 or more siblings compared to the rest of the sample (95% C.I. 11%, 38%). We estimate that a 1 SD increase in sibling educational attainment PGS corresponds to a 0.025 year increase in the index individual’s years in schooling (95% C.I. 0.013, 0.036). Our results suggest that older siblings may influence the educational attainment of younger siblings, adding to the growing evidence that effects of the environment on phenotypic variation partially reflect social effects of germline genetic variation in relatives.