Effect of average heterozygosity on the genetic distance of several Indian tribes from the Amazon region

Assessment of Genetic Diversity and Population Structure in Iranian Cannabis Germplasm

Cannabis sativa has a complex history reflected in both selection on naturally occurring compounds and historical trade routes among humans. Iran is a rich resource of natural populationswhich hold the promise to characterize historical patterns of population structure and genetic diversity within Cannabis. Recent advances in high-throughput DNA sequencing technologies have dramatically increased our ability to produce information to the point that it is now feasible to inexpensively obtain population level genotype information at a large scale. In the present investigation, we have explored the use of Genotyping-By-Sequencing (GBS) in Iranian cannabis. We genotyped 98 cannabis samples 36 from Iranian locations and 26 accessions from two germplasm collections. In total, 24,710 high-quality Single Nucleotide Polymorphisms (SNP) were identified. Clustering analysis by Principal Component Analysis (PCA) identified two genetic clusters among Iranian populations and fineSTRUCTURE analysis identified 19 populations with some geographic partitioning. We defined Iranian cannabis in two main groups using the results of the PCA and discovered some strong signal to define some locations as population according to fineSTRUCTURE analyses. However, single nucleotide variant analysis uncovered a relatively moderate level of variation among Iranian cannabis.

Correlations between heterozygosity and measures of genetic similarity: implications for understanding mate choice

There is currently considerable interest in testing the effects of genetic compatibility and heterozygosity on animal mate preferences. Evidence for either effect is rapidly accumulating, although results are not always clear-cut. However, correlations between mating preferences and either genetic similarity or heterozygosity are usually tested independently, and the possibility that similarity and heterozygosity may be confounded has rarely been taken into account. Here we show that measures of genetic similarity (allele sharing, relatedness) may be correlated with heterozygosity, using data from 441 human individuals genotyped at major loci in the major histocompatibility complex, and 281 peafowl (Pavo cristatus) individuals genotyped at 13 microsatellite loci. We show that average levels of allele sharing and relatedness are each significantly associated with heterozygosity in both humans and peafowl, that these relationships are influenced by the level of polymorphism, and that these similarity measures may correlate with heterozygosity in qualitatively different ways. We discuss the implications of these inter-relationships for interpretation of mate choice studies. It has recently become apparent that mating preferences for 'good genes' and 'compatible genes' may introduce discordant choice amongst individuals, since the optimal mate for one trait may not be optimal for the other, and our results are consistent with this idea. The inter-relationship between these measures of genetic quality also carries implications for the way in which mate choice studies are designed and interpreted, and generates predictions that can be tested in future research.

Genetic structure of Quechua-speakers of the Central Andes and geographic patterns of gene frequencies in South Amerindian populations

A sample of 141 Quechua-speaking individuals of the population of Tayacaja, in the Peruvian Central Andes, was typed for the following 16 genetic systems: ABO, Rh, MNSs, P, Duffy, AcP1, EsD, GLOI, PGM1, AK, 6-PGD, Hp, Gc, Pi, C3, and Bf. The genetic structure of the population was analyzed in relation to the allele frequencies available for other South Amerindian populations, using a combination of multivariate and multivariable techniques. Spatial autocorrelation analysis was performed independently for 13 alleles to identify patterns of gene flow in South America as a whole and in more specific geographic regions. We found a longitudinal cline for the AcP1*a and EsD*1 alleles which we interpreted as the result of an ancient longitudinal expansion of a putative ancestral population of modern Amerindians. Monmonnier's algorithm, used to identify areas of sharp genetic discontinuity, suggested a clear east-west differentiation of native South American populations, which was confirmed by analysis of the distribution of genetic distances. We suggest that this pattern of genetic structures is the consequence of the independent peopling of western and eastern South America or to low levels of gene flow between these regions, related to different environmental and demographic histories.