Separation of common environment and dominance effects with classic kinship correlation models

Abstract

Common family environmental effect (γ²) and dominance effect (d² ) are usually confounded; either or both may make the sib‐sib correlation larger than the parent‐child correlation. The classic three kinship correlations (parent‐parent, parent‐offspring, sib‐sib) can accommodate either dominance (Model D) or common family environment effects (Model C), but not both. The relationship between the various components of the three correlations of Models D and C are given. In order to include both dominance and common family environment effects, a fourth correlation, that between half‐sibs, is added to the system which enables us to separate the dominance effects from the common family environments effects. Half‐sibs may constitute a potentially new source material for study of quantitative inheritance. The principle of the constant heredity/environment ratio is discussed.     

Gene-history correlation and population structure

Correlation of gene histories in the human genome determines the patterns of genetic variation (haplotype structure) and is crucial to understanding genetic factors in common diseases. We derive closed analytical expressions for the correlation of gene histories in established demographic models for genetic evolution and show how to extend the analysis to more realistic (but more complicated) models of demographic structure. We identify two contributions to the correlation of gene histories in divergent populations: linkage disequilibrium, and differences in the demographic history of individuals in the sample. These two factors contribute to correlations at different length scales: the former at small, and the latter at large scales. We show that recent mixing events in divergent populations limit the range of correlations and compare our findings to empirical results on the correlation of gene histories in the human genome.     

Host-parasite kinship in a female-philopatric bird population: evidence from relatedness trend analysis

Conspecific brood parasitism (CBP), an alternative reproductive tactic where some females lay eggs in the nests of other females of the same species, occurs in many animals with egg care. It is particularly common in waterfowl, for reasons that are debated. Many waterfowl females nest near their birthplace, making it likely that some local females are relatives. We analyse brood parasitism in a Hudson Bay population of common eiders, testing predictions from two alternative hypotheses on the role of relatedness in CBP. Some models predict host-parasite relatedness, others predict that parasites avoid close relatives as hosts. To distinguish between the alternatives, we use a novel approach, where the relatedness of host-parasite pairs is tested against the spatial population trend in pairwise relatedness. We estimate parasitism, nest take-over and relatedness with protein fingerprinting and bandsharing analysis of egg albumen, nondestructively sampled from each new egg in the nest throughout the laying period. The results refute the hypothesis that parasites avoid laying eggs in the nests of related hosts, and corroborate the alternative of host-parasite relatedness. With an estimated r of 0.12-0.14, females laying eggs in the same nest are on average closer kin than nesting neighbour females. Absence of a population trend in female pairwise relatedness vs. distance implies that host-parasite relatedness is not only an effect of strong natal philopatry: some additional form of kin bias is also involved.     

Estimation of inbreeding,kinship and genetic distances from surnames--coastal population of middle Dalmatia,Croatia

This work was dedicated to the investigation of the population structure of the middle Dalmatia settlements: Jesenice, Mimice, Zivogos?e and Zaostrog by surname distribution study and applying the isonymous method. The surnames of males and females in marital pairs were analyzed as well as of their first and second-generation ancestors on the sample of a total of 3,024 examinees. The analyses of surnames pointed to the rates of inbreeding, kinship and genetic distances of the populations. Although the values of the inbreeding coefficient are high in all the four settlements, the inbreeding coefficient is exceptionally high in Mimice. A total kinship coefficient for the four settlements speaks also in favor of the high rate of kinship in the examined settlements, i.e. of the high rate of the reproductive isolation of the whole region during the analyzed period. The reasons for such high coefficients are natural features of the examined region (the mountains of Mosor, Biokovo and Rili?), poor traffic connection of this region in the past, the patrilineal mode of inheritance and the demographic specifics of the population. The matrix of genetic distances between examined settlement pairs reveals that Mimice, a settlement with the highest share of isonymous marriages, shows the greatest distances in comparison to the other settlements. On the other hand, Jesenice, Zivogos?e and Zaostrog are characterized by small genetic distances, which is the fact that speaks in favor of their genetic homogenization and "openness" toward interpopulational migrations, i.e. the gene flow.     

Temporally stable genetic variability and dynamic kinship structure in a fluctuating population of the root vole Microtus oeconomus

Genetic variability, kin structure and demography of a population are mutually dependent. Population genetic theory predicts that under demographically stable conditions, neutral genetic variability reaches equilibrium between gene flow and drift. However, density fluctuations and non‐random mating, resulting e.g. from kin clustering, may lead to changes in genetic composition over time. Theoretical models also predict that changes in kin structure may affect aggression level and recruitment, leading to density fluctuations. These predictions have been rarely tested in natural populations. The aim of this study was to analyse changes in genetic variability and kin structure in a local population of the root vole (Microtus oeconomus) that underwent a fourfold change in mean density over a 6‐year period. Intensive live‐trapping resulted in sampling 88% of individuals present in the study area, as estimated from mark–recapture data. Based on 642 individual genotypes at 20 microsatellite loci, we compared genetic variability and kin structure of this population between consecutive years. We found that immigration was negatively correlated with density, while the number of kin groups was positively correlated with density. This is consistent with theoretical predictions that changes in kin structure play an important role in population fluctuations. Despite the changes in density and kin structure, there was no genetic differentiation between years. Population‐level genetic diversity measures did not significantly vary in time and remained relatively high (H_E range: 0.72–0.78). These results show that a population that undergoes significant demographic and social changes may maintain high genetic variability and stable genetic composition.