Related Parents Research Articles

Parental Relatedness and Survival of Pacific Oysters from a Naturalized Population

Inbreeding has profound implications in fields ranging from evolutionary biology to medicine. Most cultured aquatic species are only partially domesticated and highly fecund and are, therefore, expected to have higher genetic load and more severe inbreeding depression than species with lower fecundity and/or longer histories of domestication. Marine bivalves such as oysters are extreme in this regard, and previous studies have demonstrated that self-fertilization, brother/sister matings, and cousin/cousin matings in Pacific oysters (Crassostrea gigas) reduce growth and survival. It is unclear, however, whether these effects can be extrapolated to lower levels of consanguinity such as those expected in natural populations or the founders used to initiate cultured strains or selective breeding efforts. To address this without the need for extensive pedigree information, we studied inbreeding in a naturalized population of Pacific oysters using molecular marker-based estimates of parental relatedness calculated from multilocus microsatellite genotypes. We produced 34 full-sib families using randomly mated parents collected from a naturalized population in Dabob Bay (Washington, USA) and planted them in intertidal and subtidal conditions in Dabob Bay and Yaquina Bay (Oregon, USA). Using 16 microsatellite loci, we estimated the degree of inbreeding of each pair's progeny in three ways: (1) identity (I ) or the expected homozygosity of the progeny based on their parents' genotypes estimated using the IDENTIX program, (2) a moment-based estimator of the pair-wise coefficient of relatedness (W ) of each parental pair estimated using the MER program of Wang, and (3) a modified estimator of the pair-wise coefficient of relatedness (K ) designed specifically to accommodate null alleles, which were common in the Dabob Bay population and estimated using the ML-RELATE by Kalinowski. Using a composite analysis of variance approach to partition the total among-family variation into components attributable to inbreeding and all other family-level effects, we found statistically significant negative relationships between all three estimators of inbreeding and the survival of their progeny when we analyzed all location/exposure combinations simultaneously and in 7 of the 12 separate tests examining each location/exposure combination separately. However, for 4 of the 5 nonsignificant tests, P < 0.07 using K estimator of relatedness, which makes the potentially unreasonable assumption that all parents have inbreeding coefficients (F) of zero. Further, these relationships were strongest at the site with the highest mortality, indicating that inbreeding depression may be more severe in a more stressful environment. Finally, we briefly outline potential strategies for using molecular marker-based estimates of relatedness to improve the genetic composition of new founder populations, incorporation of relatedness information in selective breeding efforts, and minimizing inbreeding effects in established cultured oyster populations.

Evolution of Adaptation and Mate Choice: Parental Relatedness Affects Expression of Phenotypic Variance in a Natural Population

Mating between relatives generally results in reduced offspring viability or quality, suggesting that selection should favor behaviors that minimize inbreeding. However, in natural populations where searching is costly or variation among potential mates is limited, inbreeding is often common and may have important consequences for both offspring fitness and phenotypic variation. In particular, offspring morphological variation often increases with greater parental relatedness, yet the source of this variation, and thus its evolutionary significance, are poorly understood. One proposed explanation is that inbreeding influences a developing organism’s sensitivity to its environment and therefore the increased phenotypic variation observed in inbred progeny is due to greater inputs from environmental and maternal sources. Alternatively, changes in phenotypic variation with inbreeding may be due to additive genetic effects alone when heterozygotes are phenotypically intermediate to homozygotes, or effects of inbreeding depression on condition, which can itself affect sensitivity to environmental variation. Here we examine the effect of parental relatedness (as inferred from neutral genetic markers) on heritable and nonheritable components of developmental variation in a wild bird population in which mate choice is often constrained, thereby leading to inbreeding. We found greater morphological variation and distinct contributions of variance components in offspring from highly related parents: inbred offspring tended to have greater environmental and lesser additive genetic variance compared to outbred progeny. The magnitude of this difference was greatest in late-maturing traits, implicating the accumulation of environmental variation as the underlying mechanism. Further, parental relatedness influenced the effect of an important maternal trait (egg size) on offspring development. These results support the hypothesis that inbreeding leads to greater sensitivity of development to environmental variation and maternal effects, suggesting that the evolutionary response to selection will depend strongly on mate choice patterns and population structure.

Genetic relatedness of mates does not predict patterns of parentage in North American red squirrels

Previously limited to laboratory studies, the deleterious effects of inbreeding are now being revealed in a number of wild systems. Female North American red squirrels, Tamiasciurus hudsonicus, show high levels of multimale mating and little to no overt precopulatory mate selection. We hypothesized that the negative repercussions of inbreeding should select for a female's ability to select sperm from more distantly related males. Consequently, successful sires should be less genetically related to the female than are unsuccessful males. We tested this hypothesis using both an analysis of absolute success among all copulating males and also relative success of sires within multiply sired litters. Pairwise genetic relatedness and paternity were determined through molecular analysis of tissue samples collected from reproductive females, copulating males and resultant offspring. In contrast to other systems, we found no evidence that the genetic similarity of mates predicts patterns of parentage in red squirrels. Genetic relatedness did not predict whether a copulating male would sire any offspring, and relative success of sires within multiply sired litters was unrelated to their relatedness to the dam of the litter. Furthermore, selection for inbreeding avoidance mechanisms may be minimal, as there were no observable negative fitness repercussions to inbreeding. We detected no relationship between the genetic relatedness of an offspring's parents and its neonatal mass, growth rate or survival to reproductive age. In red squirrels, we found no evidence of parentage patterns based on genetic similarity of mates, and this phenomenon may be less universal than previously thought.

Inbreeding effects on growth and survival in a naturalized population of the Pacific oyster (Crassostrea gigas) revealed using molecular marker-based estimates of parental relatedness

Inbreeding effects on growth and survival in a naturalized population of the Pacific oyster (Crassostrea gigas) revealed using molecular marker-based estimates of parental relatedness

The Effects of Inbreeding on Male Courtship Behaviour and Coloration in Guppies

AbstractDespite an extensive literature on inbreeding depression in a variety of traits, relatively little is known about the effects of inbreeding on patterns of sexual behaviour. In this study, we use the guppy Poecilia reticulata to investigate the influence of parental relatedness (full‐sib. vs. unrelated matings) on sexual behaviour and colour pattern variation in adult male offspring. Our results revealed that one generation of full‐sibling mating resulted in a strong decline in male sexual motivation (courtship intensity and following behaviour) and mating success (number of successful copulations and insemination success – as estimated by the frequency of post‐copulatory jerks after mating), but we detected no significant influence of inbreeding on colour pattern variation. Our finding that sexual ornamentation (colour) did not show similar inbreeding depression to courtship behaviour may be due to differences in the genetic basis of these traits. Our findings indicate that courtship can be a sensitive indicator of genetic stress and add to an emerging picture that sexually selected traits can be severely affected by inbreeding depression.

How female reed buntings benefit from extra‐pair mating behaviour: testing hypotheses through patterns of paternity in sequential broods

Extra-pair paternity is an important aspect of reproductive strategies in many species of birds. Given that in most species females control whether fertilization occurs, they are expected to benefit in some way from the extra-pair matings. In this study we use patterns of extra-pair paternity (EPP) in broods of individual reed buntings (Emberiza schoeniclus), both within and between seasons, to test four hypothesized female benefits: (1) assessing potential future partners and seeking (2) genetic diversity (3) good genes, or (4) compatible genes. Reed buntings are socially monogamous, multibrooded passerines with extremely high levels of extra-pair paternity. We studied a population of reed buntings in the Netherlands in 2002 and 2003; 51% of offspring in 74% of nests were extra-pair. We showed that patterns of EPP did not support the first and second hypotheses, since females did not form a pair with previous extra-pair partners, EPP was not evenly distributed among broods and more broods than expected were sired by a single male. Furthermore, there was no relation between a male's within- and extra-pair fertilization success, no consistency in EPP between breeding attempts, no effect of parental relatedness on EPP and several cases of reciprocal paternity. These patterns do not support the good genes hypothesis and are most consistent with the genetic compatibility hypothesis. However, our previous finding that older males are more successful in gaining EPP, suggests some effect of good genes. These hypotheses need not be mutually exclusive, as females may select compatible males above a certain quality threshold (e.g. old males).

No relationship between microsatellite variation and neonatal fitness in Antarctic fur seals, Arctocephalus gazella

Published studies of wild vertebrate populations have almost universally reported positive associations between genetic variation measured at microsatellite loci and fitness, creating the impression of ubiquity both in terms of the species and the traits involved. However, there is concern that this picture may be misleading because negative results frequently go unpublished. Here, we analyse the relationship between genotypic variation at nine highly variable microsatellite loci and neonatal fitness in 1070 Antarctic fur seal pups born at Bird Island, South Georgia. Despite our relatively large sample size, we find no significant association between three different measures of heterozygosity and two fitness traits, birth weight and survival. Furthermore, increasing genetic resolution by calculating parental relatedness also yields no association between genetic variation and fitness. Our findings are consistent with necropsy data showing that most pups die from starvation or trauma, conditions that are unlikely to be influenced strongly by genetic factors, particularly if the benefits of high heterozygosity are linked to immune-related genes.

Insect Biodiversity on Plant Hybrids Within the Hawaiian Silversword Alliance (Asteraceae: Heliantheae-Madiinae)

Patterns of arthropod richness and diversity were studied across six hybrid zones within the silversword alliance (Asteraceae: Heliantheae-Madiinae), an adaptive radiation of endemic Hawaiian plants. Hybrid zones spanned a range of parental plant relatedness from those in which parental types were phenotypically and genetically similar to those in which parental types were different both phenotypically and genetically. This system of hybrid zones is uniquely suited for distinguishing among alternative hypotheses that account for biodiversity of herbivores in plant hybrid zones. In the six hybrid zones studied, arthropod family-level diversity was as high or higher on hybrid plants compared with parental plants. Family-level richness was as high or higher on hybrids plants in four cases and lower on hybrids in two cases. Generally, results were consistent with hypotheses that predict either a breakdown in insect defenses in hybrid plants or an additive increase in host recognition cues in hybrids. Hypotheses that predict an increase in hybrid resistance to herbivory were supported in two cases. Measures of community similarity suggest insect communities are more similar to each other on hybrid-parent pairs than are communities on parent-parent pairs and that insect communities across interspecific hybrid zones are more similar than communities across intergeneric hybrid zones. In four zones, hybrids supported unique arthropod taxa. Because a greater or equal diversity of arthropods is found on hybrids than on parental plant taxa and because hybrid plants may represent unique environments to insects, plant hybrid zones are important targets for conserving Hawaii's native biota.

Paternity in mallards: effects of sperm quality and female sperm selection for inbreeding avoidance

Postcopulatory processes might play an important role in sexual selection. In theory, fertilization success could be controlled by females via selection of particular sperm within their reproductive tract, or it could be determined by sperm competition per se. In practice, these two mechanisms are difficult to disentangle. To assess the relative importance of both mechanisms we used artificial insemination in combination with measurements of sperm quality (swimming speed and motility) in mallards. In this species, females often lack behavioral control over copulations and hence may use postcopulatory mechanisms to optimize their reproductive output. One important factor affecting female fitness may be selection of genetically compatible males. To investigate the influence of sperm quality and parental relatedness on paternity we inseminated 12 groups of related females with a sperm mixture containing equal numbers of sperm from a brother and from an unrelated male. Paternity was independent of the relatedness of the siring male to the female but was significantly affected by long-term sperm swimming speed and motility. No interaction between relatedness and sperm quality on paternity was observed. These results suggest that female mallards are not able to select sperm on a purely genetic basis and emphasize the importance of sperm quality in gaining paternity. Copyright 2005.

Parasite-mediated heterozygote advantage in an outbred songbird population

Coevolution with parasites is thought to maintain genetic diversity in host populations. However, while there are sound theoretical reasons to expect heterozygosity and parasite resistance to be related, this pattern has generally been shown only in inbred laboratory and island populations. This leaves doubt as to whether parasite-mediated selection for genetic diversity is in fact a general process. Here we show that haematozoan parasite load is linked to two complementary measures of microsatellite variability in an outbred population of mountain white-crowned sparrows (Zonotrichia leucophrys oriantha) for which we know that parasites reduce fitness. Moreover, each of the genetic measures predicts a subtly different aspect of parasitism. Microsatellite heterozygosity is related to an individual's risk of parasitism, and mean d2 (a broader, more long-term measure of parental relatedness) to the severity of infection among parasitized individuals.

Outbreeding depression in the common frog, Rana temporaria

Theory suggests that parental relatedness is a continuous variable with a fitness optimum that we heretoforth will refer to as ‘optimal outbreeding’. In the present paper, we test this proposition from a conservation (translocation) perspective. Amphibians are facing a global decline and many amphibian populations are today small and threatened by extinction. Because genetic differentiation is often high between amphibian populations, they could be particularly sensitive to outbreeding depression, e.g. due to breakdown of locally adapted gene complexes. We tested if outbreeding would reduce fitness in common frogs, Rana temporaria, crossed from a large and an isolated, small population, separated by 130 km, using artificial fertilization. For females from the large population, tadpoles were significantly smaller and more malformed in crosses with males from the small population, than with males from the large population. For the small population, however, no significant paternal genetic effects could be found. The difference in response to outbreeding between populations was accompanied with significant differences in the importance of maternal effects. We conclude that care should be taken when translocating frogs between distantly related populations to avoid outbreeding depression.

EXPLORING THE RELATIONSHIP BETWEEN PARENTAL RELATEDNESS AND MALE REPRODUCTIVE SUCCESS IN THE ANTARCTIC FUR SEAL ARCTOCEPHALUS GAZELLA

Recent genetic studies of natural populations have shown that heterozygosity and other genetic estimates of parental relatedness correlate with a wide variety of fitness traits, from juvenile survival and parasite resistance to male reproductive success. Many of these traits involve health and survival, where the underlying mechanism may involve changes in the effectiveness of the immune system. However, for traits such as reproductive success, the likely mechanisms remain less obvious. In this paper, we examine the relationship between heterozygosity and a range of traits that contribute to male reproductive success, including time spent on territories and competitiveness. Our analysis is based on observational and genetic data from eight consecutive breeding seasons at a colony of the Antarctic fur seal, Arctocephalus gazella. Overall, male reproductive success was found to correlate strongly with internal relatedness (IR, a form of heterozygosity). When different components of success were analyzed, we found that IR correlates independently with reproductive longevity, time spent ashore, and competitive ability per unit mating opportunity on the study beach, with more heterozygous males being more successful. Behavioral observations were sufficiently detailed to allow examination of how daily mean IR values for males present on the beach varied within seasons and from year to year. Again, significant variation was found both among and within seasons, with more homozygous males appearing less able to hold territories in poor seasons when pup production is low and, within a season, at both the start of the season and to some extent around the peak of female estrus. Finally, we tested whether the benefits of high heterozygosity are due mainly to a genomewide effect (e.g. inbreeding depression) or to single locus heterosis by asking whether the relationship between IR and male success was robust to the removal of any single locus or to any pair of loci. Since the relationship remained significant in all cases, we favor a multilocus explanation for the effects we report.

Targeted cybridization in citrus: transfer of Satsuma cytoplasm to seedy cultivars for potential seedlessness.

CMS (cytoplasmic male sterility) can be controlled by the mitochondrion genome in higher plants, including Satsuma mandarin. Somatic fusion experiments in citrus combining embryogenic callus protoplasts of one parent with leaf protoplasts of a second parent often produce cybrid plants of the leaf parent, a phenomenon occurring most often with interspecific fusion combinations. In an attempt to practically exploit this cybridization phenomenon, we conducted somatic fusion experiments combining embryogenic suspension-derived protoplasts of Satsuma mandarin, Citrus unshiu Marc. cv. Guoqing No. 1 (G1), a male-sterile cultivar, with leaf protoplasts of other seedy types--Hirado Buntan Pink pummelo (HBP) [Citrus grandis (L.) Osbeck], Sunburst mandarin (C. reticulata Blanco), Orie Lee hybrid (C. reticulata cv. Clementine x Murcott tangor), and Murcott tangor [C. reticulata x C. sinensis (L.) Osbeck], respectively--in an attempt to generate seedless cybrids by the targeted transfer of CMS. The genetic identities of regenerated plants from all four parental combinations were determined by flow cytometry, SSR, CAPS (or PCR-RFLP), RFLP, and chloroplast-SSR analyses. Regenerated plants from the first three parental combinations were diploids, and the cybrid nature of G1 + HBP with the mitochondrion genome from G1 and the chloroplast genome from HBP was confirmed, whereas the cybrid nature of the remaining two combinations was difficult to confirm because of the close phylogenetic relatedness of both fusion parents, as expected. Plants from G1 + Murcott were confirmed as tetraploid somatic hybrids. This is the first report of targeted citrus cybrid production by symmetric fusion with male-sterile Satsuma as the callus parent and other seedy cultivars as the leaf parents.

Theory‐Based Determinants of Youth Smoking: A Multiple Influence Approach1

This study tested a broad array of determinants of smoking grounded in general social psychological theories, as well as personality and social development theories. Using data from 2,004 middle school students, all proximal and distal determinants significantly predicted smoking in the hypothesized direction. Further, hierarchical logistic regressions showed that intention to smoke, positive and negative attitudes toward smoking, impediments to smoking, self‐efficacy to resist smoking, parent norms, and academic success most strongly predicted current smoking. Hierarchical linear regressions suggested that parental relatedness, maladaptive coping strategies, depression, and low academic aspirations most strongly predicted susceptibility to smoking for those who had not yet smoked a cigarette. Global expectancies were the strongest predictor of susceptibility in low socioeconomic status students. These findings may guide the development of future theory‐based interventions that produce the greatest reductions in youth smoking.

EXPLORING THE RELATIONSHIP BETWEEN PARENTAL RELATEDNESS AND MALE REPRODUCTIVE SUCCESS IN THE ANTARCTIC FUR SEAL ARCTOCEPHALUS GAZELLA

Recent genetic studies of natural populations have shown that heterozygosity and other genetic estimates of parental relatedness correlate with a wide variety of fitness traits, from juvenile survival and parasite resistance to male reproductive success. Many of these traits involve health and survival, where the underlying mechanism may involve changes in the effectiveness of the immune system. However, for traits such as reproductive success, the likely mechanisms remain less obvious. In this paper, we examine the relationship between heterozygosity and a range of traits that contribute to male reproductive success, including time spent on territories and competitiveness. Our analysis is based on observational and genetic data from eight consecutive breeding seasons at a colony of the Antarctic fur seal, Arctocephalus gazella. Overall, male reproductive success was found to correlate strongly with internal relatedness (IR, a form of heterozygosity). When different components of success were analyzed, we found that IR correlates independently with reproductive longevity, time spent ashore, and competitive ability per unit mating opportunity on the study beach, with more heterozygous males being more successful. Behavioral observations were sufficiently detailed to allow examination of how daily mean IR values for males present on the beach varied within seasons and from year to year. Again, significant variation was found both among and within seasons, with more homozygous males appearing less able to hold territories in poor seasons when pup production is low and, within a season, at both the start of the season and to some extent around the peak of female estrus. Finally, we tested whether the benefits of high heterozygosity are due mainly to a genomewide effect (e.g. inbreeding depression) or to single locus heterosis by asking whether the relationship between IR and male success was robust to the removal of any single locus or to any pair of loci. Since the relationship remained significant in all cases, we favor a multilocus explanation for the effects we report.

Inbreeding: Disease susceptibility in California sea lions.

Inbreeding influences the response of these animals to different pathogens in the wild. Inbreeding in animals can increase their susceptibility to pathogens, but direct evidence from wild populations is scarce1,2 and it is unclear whether all pathogens are affected equally. Here we analyse rescued California sea lions afflicted with a range of different pathogens, and find that sick animals have higher-than-normal parental relatedness, with the extent varying among disease classes. Our findings indicate that mortality in natural populations may not be entirely random and that inbred individuals could act as more effective reservoirs of infectious agents.

The influence of parental relatedness on reproductive success.

The relationship between fitness and parental similarity has been dominated by studies of how inbreeding depression lowers fecundity in incestuous matings. A widespread implicit assumption is that adult fitness (reproduction) of individuals born to parents who are not unusually closely related is more or less equal. Examination of three long-lived vertebrates, the long-finned pilot whale, the grey seal and the wandering albatross reveals significant negative relationships between parental similarity and genetic estimates of reproductive success. This effect could, in principle, be driven by a small number of low quality, inbred individuals. However, when the data are partitioned into individuals with above average and below average parental similarity, we find no evidence that the slopes differ, suggesting that the effect is more or less similar across the full range of parental similarity values. Our results thus uncover a selective pressure that favours not only inbreeding avoidance, but also the selection of maximally dissimilar mates.

Sperm Choice and Sperm Competition: Suggestions for Field and Laboratory Studies

The recent explosion of research on sperm competition, and the emerging idea that females may control paternity of their offspring via sperm choice, raise many methodological questions. One central issue is the role of inbreeding-induced mortality of offspring. We present a theoretical model which makes the relationship between parental relatedness and offspring mortality explicit, and discuss its applicability as a null model of offspring mortality in studies of sperm competition/ sperm choice. We also discuss the extent to which partner relatedness may be overlooked in studies of behavioural ecology in natural populations, and the extent to which a failure to mimic crucial aspects of sperm competition scenarios in the wild may limit our ability to make evolutionary inferences from laboratory experiments.

THE RELATIONSHIP BETWEEN CROSS SUCCESS AND SPATIAL PROXIMITY OF EUCALYPTUS GLOBULUS SSP. GLOBULUS PARENTS.

The genetic structure of Eucalyptus globulus forest was examined using progeny vigor as an indirect measure of parental relatedness. Seven trees were crossed with pollen from trees: 0 m (seifing); 21 m (nearest flowering neighbors), 250 m, 500 m, 1 km, 10 km, and 100 km away from the female. Only selfing depressed seed set. Growth of the 21 m progenies was intermediate to selfing and the longer distance pollinations, suggesting tight family clusters occur due to limited seed dispersal. Under this structure biparental inbreeding may be common, however, the cumulative impact of inbreeding seems negligible as relatedness did not appear to decline with distance between mates beyond 50 m.

Differential Effects of Inbreeding at Juvenile and Adult Life-History Stages in Peromyscus polionotus

Inbreeding depression traditionally has been measured at early life-history stages, such as neonatal or juvenile viability or deficits in growth and development. I investigated additional fitness components by evaluating impact of inbreeding on reproductive success of adult females in a captive colony of oldfield mice (Peromyscus polionotus subgriseus and P. p. rhoadsi). By first conducting analyses on only inbreeding of litters (i.e., relatedness of parents) and then adding maternal effects (mother's inbreeding coefficient independent of parental relatedness, parity, and maternal inactivity), I illustrated effect of inbreeding on life-history characters that were manifested in adulthood. Young in inbred litters (f > 0.1) tended to be smaller than young in outbred litters, but inbred litters did not exhibit any decrements in survival probability. Number of young raised to weaning from inbred and outbred litters did not differ. Inbred females (inbreeding coefficient f > 0.1) reared significantly fewer young than did outbred females (f < 0.1) (independent of whether parents were related and therefore independent of whether young themselves were inbred). Differences between the two subspecies were found for a number of fitness traits. These differences are attributed to chance differences in genetic makeup of founder stocks (founder effect). Examining inbreeding effects only at a single life-history stage (i.e., during the juvenile period) and only on a single fitness trait (juvenile viability) may result in serious underestimation of the extent of inbreeding depression.