On the testing of Hardy-Weinberg proportions and equality of allele frequencies in males and females at biallelic genetic markers

Standard statistical tests for equality of allele frequencies in males and females and tests for Hardy-Weinberg equilibrium are tightly linked by their assumptions. Tests for equality of allele frequencies assume Hardy-Weinberg equilibrium, whereas the usual chi-square or exact test for Hardy-Weinberg equilibrium assume equality of allele frequencies in the sexes. In this paper, we propose ways to break this interdependence in assumptions of the two tests by proposing an omnibus exact test that can test both hypotheses jointly, as well as a likelihood ratio approach that permits these phenomena to be tested both jointly and separately. The tests are illustrated with data from the 1000 Genomes project.Peer ReviewedPostprint (author's final draft

Multi-allelic exact tests for Hardy-Weinberg equilibrium that account for gender

Statistical tests for Hardy–Weinberg equilibrium are important elementary tools in genetic data analysis. X-chromosomal variants have long been tested by applying autosomal test procedures to females only, and gender is usually not considered when testing autosomal variants for equilibrium. Recently, we proposed specific Xchromosomal exact test procedures for bi-allelic variants that include the hemizygous males, as well as autosomal tests that consider gender. In this study, we present the extension of the previous work for variants with multiple alleles. A full enumeration algorithm is used for the exact calculations of tri-allelic variants. For variants with many alternate alleles, we use a permutation test. Some empirical examples with data from the 1,000 genomes project are discussed.Peer ReviewedPostprint (published version

The transitivity of the Hardy-Weinberg law

The Hardy–Weinberg law is shown to be transitive in the sense that a multi-allelic polymorphism that is in equilibrium will retain its equilibrium status if any allele together with its corresponding genotypes is deleted from the population. Similarly, the transitivity principle also applies if alleles are joined, which leads to the summation of allele frequencies and their corresponding genotype frequencies. These basic polymorphism properties are intuitive, but they have apparently not been formalized or investigated. This article provides a straightforward proof of the transitivity principle, and its usefulness in genetic data analysis is explored, using high-quality autosomal microsatellite databases from the US National Institute of Standards and Technology. We address the reduction of multi-allelic polymorphisms to variants with fewer alleles, two in the limit. Equilibrium test results obtained with the original and reduced polymorphisms are generally observed to be coherent, in particular when results obtained with length-based and sequence-based microsatellites are compared. We exploit the transitivity principle in order to identify disequilibrium-related alleles, and show its usefulness for detecting population substructure and genotyping problems that relate to null alleles and allele imbalance.Peer ReviewedPostprint (published version

A Unified Characterization of Population Structure and Relatedness.

Many population genetic activities, ranging from evolutionary studies to association mapping, to forensic identification, rely on appropriate estimates of population structure or relatedness. All applications require recognition that quantities with an underlying meaning of allelic dependence are not defined in an absolute sense, but instead are made "relative to" some set of alleles other than the target set. The 1984 Weir and Cockerham [Formula: see text] estimate made explicit that the reference set of alleles was across populations, whereas standard kinship estimates do not make the reference explicit. Weir and Cockerham stated that their [Formula: see text] estimates were for independent populations, and standard kinship estimates have an implicit assumption that pairs of individuals in a study sample, other than the target pair, are unrelated or are not inbred. However, populations lose independence when there is migration between them, and dependencies between pairs of individuals in a population exist for more than one target pair. We have therefore recast our treatments of population structure, relatedness, and inbreeding to make explicit that the parameters of interest involve the differences in degrees of allelic dependence between the target and the reference sets of alleles, and so can be negative. We take the reference set to be the population from which study individuals have been sampled. We provide simple moment estimates of these parameters, phrased in terms of allelic matching within and between individuals for relatedness and inbreeding, or within and between populations for population structure. A multi-level hierarchy of alleles within individuals, alleles between individuals within populations, and alleles between populations, allows a unified treatment of relatedness and population structure. We expect our new measures to have a wide range of applications, but we note that their estimates are sensitive to rare or private variants: some population-characterization applications suggest exploiting those sensitivities, whereas estimation of relatedness may best use all genetic markers without filtering on minor allele frequency

How to estimate kinship.

The concept of kinship permeates many domains of fundamental and applied biology ranging from social evolution to conservation science to quantitative and human genetics. Until recently, pedigrees were the gold standard to infer kinship, but the advent of next-generation sequencing and the availability of dense genetic markers in many species make it a good time to (re)evaluate the usefulness of genetic markers in this context. Using three published data sets where both pedigrees and markers are available, we evaluate two common and a new genetic estimator of kinship. We show discrepancies between pedigree values and marker estimates of kinship and explore via simulations the possible reasons for these. We find these discrepancies are attributable to two main sources: pedigree errors and heterogeneity in the origin of founders. We also show that our new marker-based kinship estimator has very good statistical properties and behaviour and is particularly well suited for situations where the source population is of small size, as will often be the case in conservation biology, and where high levels of kinship are expected, as is typical in social evolution studies

Modelling single nucleotide effects in phosphoglucose isomerase on dispersal in the Glanville fritillary butterfly: coupling of ecological and evolutionary dynamics

Dispersal comprises a complex life-history syndrome that influences the demographic dynamics of especially those species that live in fragmented landscapes, the structure of which may in turn be expected to impose selection on dispersal. We have constructed an individual-based evolutionary sexual model of dispersal for species occurring as metapopulations in habitat patch networks. The model assumes correlated random walk dispersal with edge-mediated behaviour (habitat selection) and spatially correlated stochastic local dynamics. The model is parametrized with extensive data for the Glanville fritillary butterfly. Based on empirical results for a single nucleotide polymorphism (SNP) in the phosphoglucose isomerase (Pgi) gene, we assume that dispersal rate in the landscape matrix, fecundity and survival are affected by a locus with two alleles, A and C, individuals with the C allele being more mobile. The model was successfully tested with two independent empirical datasets on spatial variation in Pgi allele frequency. First, at the level of local populations, the frequency of the C allele is the highest in newly established isolated populations and the lowest in old isolated populations. Second, at the level of sub-networks with dissimilar numbers and connectivities of patches, the frequency of C increases with decreasing network size and hence with decreasing average metapopulation size. The frequency of C is the highest in landscapes where local extinction risk is high and where there are abundant opportunities to establish new populations. Our results indicate that the strength of the coupling of the ecological and evolutionary dynamics depends on the spatial scale and is asymmetric, demographic dynamics having a greater immediate impact on genetic dynamics than vice versa

The Colletotrichum boninense species complex

Although only recently described, Colletotrichum boninense is well established in literature as an anthracnose pathogen or endophyte of a diverse range of host plants worldwide. It is especially prominent on members of Amaryllidaceae, Orchidaceae, Proteaceae and Solanaceae. Reports from literature and preliminary studies using ITS sequence data indicated that C. boninense represents a species complex. A multilocus molecular phylogenetic analysis (ITS, ACT, TUB2, CHS-1, GAPDH, HIS3, CAL) of 86 strains previously identified as C. boninense and other related strains revealed 18 clades. These clades are recognised here as separate species, including C. boninense s. str., C. hippeastri, C. karstii and 12 previously undescribed species, C. annellatum, C. beeveri, C. brassicicola, C. brasiliense, C. colombiense, C. constrictum, C. cymbidiicola, C. dacrycarpi, C. novae-zelandiae, C. oncidii, C. parsonsiae and C. torulosum. Seven of the new species are only known from New Zealand, perhaps reflecting a sampling bias. The new combination C. phyllanthi was made, and C. dracaenae Petch was epitypified and the name replaced with C. petchii. Typical for species of the C. boninense species complex are the conidiogenous cells with rather prominent periclinal thickening that also sometimes extend to form a new conidiogenous locus or annellations as well as conidia that have a prominent basal scar. Many species in the C. boninense complex form teleomorphs in culture

Unravelling Colletotrichum species associated with Camellia : employing ApMat and GS loci to resolve species in the C. gloeosporioides complex

We investigated the phylogenetic diversity of 144 Colletotrichum isolates associated with symptomatic and asymptomatic tissues of Camellia sinensis and other Camellia spp. from seven provinces in China (Fujian, Guizhou, Henan, Jiangxi, Sichuan, Yunnan, Zhejiang), and seven isolates obtained from other countries, including Indonesia, UK, and the USA. Based on multi-locus (ACT, ApMat, CAL, GAPDH, GS, ITS, TUB2) phylogenetic analyses and phenotypic characters, 11 species were distinguished, including nine well-characterised species (C. alienum, C. boninense, C. camelliae, C. cliviae, C. fioriniae, C. fructicola, C. gloeosporioides, C. karstii, C. siamense), and two novel species (C. henanense and C. jiangxiense). Of these, C. camelliae proved to be the most dominant and probably host specific taxon occurring on Camellia. An epitype is also designated for the latter species in this study. Colletotrichum jiangxiense is shown to be phylogenetically closely related to the coffee berry pathogen C. kahawae subsp. kahawae. Pathogenicity tests and the pairwise homoplasy index test suggest that C. jiangxiense and C. kahawae subsp. kahawae are two independent species. This study represents the first report of C. alienum and C. cliviae occurring on Camellia sinensis. In addition, our study demonstrated that the combined use of the loci ApMat and GS in a phylogenetic analysis is able to resolve all currently accepted species in the C. gloeosporioides species complex.The external Cooperation Program of CAS (GJHZ1310), the NSFC (31322001 & 31400017), and Project for Fundamental Research on Science and Technology, MOST (2014FY120100). Yong Wang acknowledged Guizhou Province (Grant 20113045) for supporting his investigation on foliar pathogens.http:// www.ingentaconnect.com/content/nhn/pimjam2016Forestry and Agricultural Biotechnology Institute (FABI)Microbiology and Plant Patholog

Unravelling Colletotrichum species associated with Camellia : employing ApMat and GS loci to resolve species in the C. gloeosporioides complex

We investigated the phylogenetic diversity of 144 Colletotrichum isolates associated with symptomatic and asymptomatic tissues of Camellia sinensis and other Camellia spp. from seven provinces in China (Fujian, Guizhou, Henan, Jiangxi, Sichuan, Yunnan, Zhejiang), and seven isolates obtained from other countries, including Indonesia, UK, and the USA. Based on multi-locus (ACT, ApMat, CAL, GAPDH, GS, ITS, TUB2) phylogenetic analyses and phenotypic characters, 11 species were distinguished, including nine well-characterised species (C. alienum, C. boninense, C. camelliae, C. cliviae, C. fioriniae, C. fructicola, C. gloeosporioides, C. karstii, C. siamense), and two novel species (C. henanense and C. jiangxiense). Of these, C. camelliae proved to be the most dominant and probably host specific taxon occurring on Camellia. An epitype is also designated for the latter species in this study. Colletotrichum jiangxiense is shown to be phylogenetically closely related to the coffee berry pathogen C. kahawae subsp. kahawae. Pathogenicity tests and the pairwise homoplasy index test suggest that C. jiangxiense and C. kahawae subsp. kahawae are two independent species. This study represents the first report of C. alienum and C. cliviae occurring on Camellia sinensis. In addition, our study demonstrated that the combined use of the loci ApMat and GS in a phylogenetic analysis is able to resolve all currently accepted species in the C. gloeosporioides species complex.The external Cooperation Program of CAS (GJHZ1310), the NSFC (31322001 & 31400017), and Project for Fundamental Research on Science and Technology, MOST (2014FY120100). Yong Wang acknowledged Guizhou Province (Grant 20113045) for supporting his investigation on foliar pathogens.http:// www.ingentaconnect.com/content/nhn/pimjam2016Forestry and Agricultural Biotechnology Institute (FABI)Microbiology and Plant Patholog

Mitochondrial diversity analysis of Glossina palpalis gambiensis from Mali and Senegal

West African riverine tsetse populations of Glossina palpalis gambiensis Vanderplank (Diptera: Glossinidae) were investigated for gene flow, inferred from mitochondrial diversity in samples of 69 flies from Senegal and 303 flies from three river drainages in Mali. Four polymorphic mitochondrial loci were scored. Mean haplotype diversities were 0.30 in Mali and 0.18 over both Mali and Senegal. These diversities estimate the probabilities that two randomly chosen tsetse have different haplotypes. Substantial rates of gene flow were detected among flies sampled along tributaries belonging to the river basins of the Senegal, Niger, and Bani in Mali. There was virtually no gene flow between tsetse in Senegal and Mali. No seasonal effects on gene flow were detected. The implications of these preliminary findings for the implementation of area-wide integrated pest management (AW-IPM) programmes against riverine tsetse in West Africa are discussed