Genetic assessment of spatiotemporal evolutionary relationships and stocking effects in grayling (Thymallus thymallus, Salmonidae)

Domestically reared introduced (or escaped) individuals can have detrimental genetic effects on the indigenous populations into which they are released. Consequently, numerous studies have attempted to estimate whether non-native specimens have contributed to the gene pool of wild populations. So far, the key limiting factor of such studies has been their lack of appropriate baseline genetic material. Here, microsatellite DNA analyses of historical scale samples and contemporary wild and introduced populations were used to assess spatiotemporal population structure and stocking effects among endangered Lake Saimaa (eastern Finland) grayling ( Thymallus thymallus , Salmonidae). Significant decreases in genetic differentiation were detected between wild and introduced populations since the commencement of stocking in 1986. Accordingly, up to 15% of the contemporary wild grayling were confidently identified to be of pure hatchery origin, and recent hybridization between the hatchery and indigenous individuals appeared likely. Despite these clear genetic imprints of stocking, the contemporary populations exhibited evolutionary relationships congruent with the sampling locations, and up to 73% of contemporary individuals were identified to be of pure indigenous origin. The use of historical baseline material should prove efficient for monitoring gene flow between domesticated and wild populations in other species also, e.g. salmonids, game animals and plants.     

Differential admixture in Latin American populations and its impact on the study of colorectal cancer

Genome-wide association studies focused on searching genes responsible for several diseases. Admixture mapping studies proposed a more efficient alternative capable of detecting polymorphisms contributing with a small effect on the disease risk. This method focuses on the higher values of linkage disequilibrium in admixed populations. To test this, we analyzed 10 genomic regions previously defined as related with colorectal cancer among nine populations and studied the variation pattern of haplotypic structures and heterozygosity values on seven categories of SNPs. Both analyses showed differences among chromosomal regions and studied populations. Admixed Latin-American samples generally show intermediate values. Heterozygosity of the SNPs grouped in categories varies more in each gene than in each population. African related populations have more blocks per chromosomal region, coherently with their antiquity. In sum, some similarities were found among Latin American populations, but each chromosomal region showed a particular behavior, despite the fact that the study refers to genes and regions related with one particular complex disease. This study strongly suggests the necessity of developing statistical methods to deal with di- or tri-hybrid populations, as well as to carefully analyze the different historic and demographic scenarios, and the different characteristics of particular chromosomal regions and evolutionary forces.     

Biological races in humans

Races may exist in humans in a cultural sense, but biological concepts of race are needed to access their reality in a non-species-specific manner and to see if cultural categories correspond to biological categories within humans. Modern biological concepts of race can be implemented objectively with molecular genetic data through hypothesis-testing. Genetic data sets are used to see if biological races exist in humans and in our closest evolutionary relative, the chimpanzee. Using the two most commonly used biological concepts of race, chimpanzees are indeed subdivided into races but humans are not. Adaptive traits, such as skin color, have frequently been used to define races in humans, but such adaptive traits reflect the underlying environmental factor to which they are adaptive and not overall genetic differentiation, and different adaptive traits define discordant groups. There are no objective criteria for choosing one adaptive trait over another to define race. As a consequence, adaptive traits do not define races in humans. Much of the recent scientific literature on human evolution portrays human populations as separate branches on an evolutionary tree. A tree-like structure among humans has been falsified whenever tested, so this practice is scientifically indefensible. It is also socially irresponsible as these pictorial representations of human evolution have more impact on the general public than nuanced phrases in the text of a scientific paper. Humans have much genetic diversity, but the vast majority of this diversity reflects individual uniqueness and not race.     

Effects of English admixture and geographic distance on anthropometric variation and genetic structure in 19th-century Ireland

The analysis of anthropometric data often allows investigation of patterns of genetic structure in historical populations. This paper focuses on interpopulational anthropometric variation in seven populations in Ireland using data collected in the 1890s. The seven populations were located within a 120-km range along the west coast of Ireland and include islands and mainland isolates. Two of the populations (the Aran Islands and Inishbofin) have a known history of English admixture in earlier centuries. Ten anthropometric measures (head length, breadth, and height; nose length and breadth; bizygomatic and bigonial breadth; stature; hand length; and forearm length) on 259 adult Irish males were analyzed following age adjustment. Discriminant and canonical variates analysis were used to determine the degree and pattern of among-group variation. Mahalanobis' distance measure, D2, was computed between each pair of populations and compared to distance measures based on geographic distance and English admixture (a binary measure indicating whether either of a pair of populations had historical indications of admixture). In addition, surname frequencies were used to construct distance measures based on random isonymy. Correlations were computed between distance measures, and their probabilities were derived using the Mantel matrix permutation method. English admixture has the greatest effect on anthropometric variation among these populations, followed by geographic distance. The correlation between anthropometric distance and geographic distance is not significant (r = -0.081, P = .590), but the correlation of admixture and anthropometric distance is significant (r = 0.829, P = .047). When the two admixed populations are removed from the analysis the correlation between geographic and anthropometric distance becomes significant (r = 0.718, P = .025). Isonymy distance shows a significant correlation with geographic distance (r = 0.425, P = .046) but not with admixture distance (r = -0.052, P = .524). The fact that anthropometrics show past patterns of gene flow and surnames do not reflects the greater impact of stochastic processes on surnames, along with the continued extinction of surnames. This study shows that 1) anthropometrics can be extremely useful in assessing population structure and history, 2) differential gene flow into populations can have a major impact on local genetic structure, and 3) microevolutionary processes can have different effects on biological characters and surnames.     

Social class,admixture, and skin color variation in Mexican-Americans and Anglo-Americans living in San Antonio,Texas

Social class may act in different ways as a barrier to gene flow in urban populations, depending on ethnicity. We test the hypothesis that biological variation is affected by social class subdivision using skin reflectance data collected for 393 Anglo-American and 930 Mexican-American adults in the major urban population of San Antonio, Texas. Two socioeconomic groups were sampled for the Anglo-American population: a middle-income transitional group and a high-income suburban group. In addition, we sampled a third socioeconomic group for Mexican-Americans: a low income barrio. Sex and age effects on skin color are minimal. Social class has no effect on skin color variation for Anglo-Americans, whereas there is a highly significant effect on social class subdivision for Mexican-Americans. Admixture estimates were derived from skin reflectance data and show that the proportion of native American ancestry decreases as social class increases.     

HYBRID SPECIATION AND INDEPENDENT EVOLUTION IN LINEAGES OF ALPINE BUTTERFLIES

The power of hybridization between species to generate variation and fuel adaptation is poorly understood despite long‐standing interest. There is, however, increasing evidence that hybridization often generates biodiversity, including via hybrid speciation. We tested the hypothesis of hybrid speciation in butterflies occupying extreme, high‐altitude habitats in four mountain ranges in western North America with an explicit, probabilistic model, and genome‐wide DNA sequence data. Using this approach, in concert with ecological experiments and observations and morphological data, we document three lineages of hybrid origin. These lineages have different genome admixture proportions and distinctive trait combinations that suggest unique and independent evolutionary histories.     

Gene flow and variation in stature and craniofacial dimensions among indigenous populations of southern Mexico, Guatemala, and Honduras

Populations with histories of outbreeding tend to be taller even in the face of seemingly unchanged health and nutritional circumstances, while inbreeding generally results in a negative correlation between body dimensions and level of inbreeding. Populations that have experienced a positive secular trend in stature and maturation typically have histories of higher outbreeding rates in combination with improved nutritional, health, and economic conditions, suggesting a genetic-environment interaction. In general, Middle American Indians have not experienced a secular trend in stature, nor a substantial increase in their standard of living, but they have experienced varying degrees of admixture with Spanish and African populations since the Spanish Conquest. The relationship between estimated gene flow and variation in several anthropometric dimensions is thus considered in indigenous Mesoamerican populations. Available data on height, sitting height, craniofacial dimensions, and admixture rate of Indian populations from southern Mexico, Guatemala, and Honduras were assembled from the literature. The population mean data on 3,371 adults from 23 populations for males and 18 for females were analyzed by regression with anthropometry as the dependent variable, and log10 of admixture as the independent variable. Admixture was less than or equal to 28.9% in this study and is suggestive of a primarily traditional Indian cultural and economic base. The results suggest that populations with higher admixture tend to be taller, and that the increase in stature is due to greater subischial length in both sexes. A decrease in nasion-menton height, and an increase in nasal breadth, nasal height, and the nasal index is suggested for the dimensions of the craniofacial complex.(ABSTRACT TRUNCATED AT 250 WORDS)     

Intertribal gene flow between the Ye'cuana and Yanomama: genetic analysis of an admixed village

Genetic exchange with a neighboring village of Ye'cuana Indians had introduced two alleles, Dia and ACPa, into the Yanomama Indian Village of Borabuk. After several generations, these alleles had reached frequencies of 0.08 and 0.10, respectively. These frequencies are puzzling because they are higher in Borabuk than in the Ye'cuana village from which they were derived. Single allele estimates of ancestral proportions obtained from either of these traits are biologically unrealistic and suggest that admixture is not a good explanation for genetic variation in Borabuk. Nevertheless, multiallelic admixture models are seen to produce credible estimates of ancestral proportions and to explain a large amount of allele frequency variation in Borabuk. When these results are compared with expectations derived froma formal pedigree analysis, good agreement is seen. Comparison of single allele estimates of ancestral proportions obtained from alleles at 11 loci, with multiallelic estimates obtained from the same 11 loci and with the pedigree-derived estimates, demonstrates the superiority of the multiallelic approach.     

Gene frequencies and admixture estimates in the state of Puebla, Mexico

Three hundred ninety-three individuals from the Universidad Autónoma de Puebla and its University Hospital were studied to determine the distribution of ABO, MN, Rh-Hr, Duffy, and Diego blood groups; red cell hemoglobin and glucose-6-phosphate dehydrogenase variants; and serum haptoglobins, albumins, and factor Bf types. With the results we estimated that the proportions of black, indian, and white genes are 10.7%, 56.3%, and 33.0%, respectively, in a trihybrid model. Reasons are given as to why the black ancestry may be artifically high, and it is pointed out that independent confirmation with other markers is needed before the figure can be accepted as a true value.