Extent Of Inbreeding Research Articles

Strong positive selection biases identity-by-descent-based inferences of recent demography and population structure in Plasmodium falciparum

Malaria genomic surveillance often estimates parasite genetic relatedness using metrics such as Identity-By-Decent (IBD), yet strong positive selection stemming from antimalarial drug resistance or other interventions may bias IBD-based estimates. In this study, we use simulations, a true IBD inference algorithm, and empirical data sets from different malaria transmission settings to investigate the extent of this bias and explore potential correction strategies. We analyze whole genome sequence data generated from 640 new and 3089 publicly available Plasmodium falciparum clinical isolates. We demonstrate that positive selection distorts IBD distributions, leading to underestimated effective population size and blurred population structure. Additionally, we discover that the removal of IBD peak regions partially restores the accuracy of IBD-based inferences, with this effect contingent on the population’s background genetic relatedness and extent of inbreeding. Consequently, we advocate for selection correction for parasite populations undergoing strong, recent positive selection, particularly in high malaria transmission settings.

Estimation of Linkage Disequilibrium, Effective Population Size, and Genetic Parameters of Phenotypic Traits in Dabieshan Cattle.

Dabieshan cattle (DBSC) are a valuable genetic resource for indigenous cattle breeds in China. It is a small to medium-sized breed with slower growth, but with good meat quality and fat deposition. Genetic markers could be used for the estimation of population genetic structure and genetic parameters. In this work, we genotyped the DBSC breeding population (n = 235) with the GeneSeek Genomic Profiler (GGP) 100 k density genomic chip. Genotype data of 222 individuals and 81,579 SNPs were retained after quality control. The average minor allele frequency (MAF) was 0.20 and the average linkage disequilibrium (LD) level (r2) was 0.67 at a distance of 0-50 Kb. The estimated relationship coefficient and effective population size (Ne) were 0.023 and 86 for the current generation. In addition, we used genotype data to estimate the genetic parameters of the population's phenotypic traits. Among them, height at hip cross (HHC) and shin circumference (SC) were rather high heritability traits, with heritability of 0.41 and 0.54, respectively. The results reflected the current cattle population's extent of inbreeding and history. Through the principal breeding parameters, genomic breeding would significantly improve the genetic progress of breeding.

Changes in the Population Genetic Structure of Captive Forest Musk Deer (Moschus Berezovskii) with the Increasing Number of Generation under Closed Breeding Conditions.

Simple SummaryForest musk deer is an endangered species. Musk produced by male musk deer is precious natural flavor and an important ingredient of traditional Chinese medicines. Forest musk deer is a territorial animal, and it is very difficult for captive forest musk deer to record the accurate pedigree using the “Breeding Management System of Rotated Mating” (BMS-RM). In the study, we examined the genetic structure of captive forest musk deer population in Barkam center, and the changes in allele diversity, heterozygosity and inbreeding coefficient with increasing generations. The results show that the population has high genetic diversity, but the genetic structure of different generations in the population shows that the extent of inbreeding is slowly increasing with increasing number of generations. This suggests that the BMS-RM is effective for maintaining genetic structure diversity of population, but captive forest musk deer in Barkam center still face the risk of inbreeding increasing. So, it is necessary to optimize the BMS-RM of captive forest musk deer or introduce male forest musk deer from an unrelated population. This study revealed the status of genetic diversity of captive forest musk deer in Barkam center and the current risks of inbreeding for providing an important understanding to the application of BMS-RM.We investigated the genetic diversity of the population of captive forest musk deer (Moschus berezovskii) in Barkam Musk Deer Breeding Centre using twelve microsatellite markers, and then analyzed the change in genetic structure of successive generation groups from the population. The data provide a new understanding for the evaluation and usage of the breeding management system. Microsatellite marker analysis detected 141 alleles with an average of 11.75 alleles for each marker. The average expected heterozygosity (HE) was 0.731. Performing an F-statistical analysis on the data showed that the genetic diversity of population decreased, and the inbreeding coefficient significant increased with the increase of generation, and FIS of the 1st generation is significantly lower than that of the second to fifth generation (p < 0.01). The result suggested that the captive population was facing the pressure of inbreeding (FIS = 0.115) and the subsequent loss of genetic diversity. Therefore, it is necessary to improve the breeding management system of the captive population by preventing close relatives from mating or inducing new individuals from the exotic population.

Timing and Extent of Inbreeding in African Goats.

Genetic characterization of African goats is one of the current priorities in the improvement of goats in the continent. This study contributes to the characterization effort by determining the levels and number of generations to common ancestors (“age”) associated with inbreeding in African goat breeds and identifies regions that contain copy number variation mistyped as being homozygous. Illumina 50k single nucleotide polymorphism genotype data for 608 goats from 31 breeds were used to compute the level and age of inbreeding at both local (marker) and global levels (FG) using a model-based approach based on a hidden Markov model. Runs of homozygosity (ROH) segments detected using the Viterbi algorithm led to ROH-based inbreeding coefficients for all ROH (FROH) and for ROH longer than 2 Mb (FROH > 2Mb). Some of the genomic regions identified as having ROH are likely to be hemizygous regions (copy number deletions) mistyped as homozygous regions. Although the proportion of these miscalled ROH is small and does not substantially affect estimates of levels of inbreeding for individual animals, the inbreeding metrics were adjusted by removing these regions from the ROH. All the inbreeding metrics varied widely across breeds, with overall means of 0.0408, 0.0370, and 0.0691 and medians of 0.0125, 0.0098, and 0.0366 for FROH, FROH > 2Mb, and FG, respectively. Several breeds (including Menabe and Sofia from Madagascar) had high proportions of recent inbreeding, while Small East African, Ethiopian, and most of the West African breeds (including West African Dwarf) had more ancient inbreeding.

Inbreeding alters context-dependent reproductive effort and immunity in male crickets.

Infection can cause hosts to drastically alter their investment in key life-history traits of reproduction and defence. Infected individuals are expected to increase investment in defence (e.g., by increasing immune function) and, due to trade-offs, investment in other traits (e.g., current reproduction) should decrease. However, the terminal investment hypothesis postulates that decreased lifespan due to infection and the associated reduction in the expectation for future offspring will favour increased investment towards current reproduction. Variation in intrinsic condition will likely influence shifts in reproductive investment post-infection, but this is often not considered in such assessments. For example, the extent of inbreeding can significantly impact an individual's lifetime fitness and may influence its reproductive behaviour following a threat of infection. Here, we investigated the effects of inbreeding status on an individual's reproductive investment upon infection, including the propensity to terminally invest. Male crickets (Gryllodes sigillatus) from four genetically distinct inbred lines and one outbred line were subjected to a treatment from an increasing spectrum of simulated infection cue intensities, using heat-killed bacteria. We then measured reproductive effort (calling effort), survival and immune function (antibacterial activity, circulating haemocytes and haemocyte microaggregations). Inbred and outbred males diverged in how they responded to a low-dose infection cue: relative to unmanipulated males, outbred males decreased calling effort, whereas inbred males increased calling effort. Moreover, we found that inbred males exhibited higher antibacterial activity and numbers of circulating haemocytes compared with outbred males. These results suggest that an individual's inbreeding status may have consequences for context-dependent shifts in reproductive strategies, such as those triggered by infection.

Genetic assessment of an isolated endemic Samango monkey (Cercopithecus albogularis labiatus) population in the Amathole Mountains, Eastern Cape Province, South Africa.

The endemic Samango monkey subspecies (Cercopithecus albogularis labiatus) inhabits small discontinuous Afromontane forest patches in the Eastern Cape, KwaZulu-Natal midlands and southern Mpumalanga Provinces in South Africa. The subspecies is affected by restricted migration between forest patches which may impact on gene flow resulting in inbreeding and possible localized extinction. Current consensus, based on habitat quality, is that C.a.labiatus can be considered as endangered as the small forest patches they inhabit may not be large enough to sustain them. The aim of this study was to conduct a molecular genetic investigation to determine if the observed isolation has affected the genetic variability of the subspecies. A total of 65 Samango monkeys (including juveniles, subadults and adults) were sampled from two localities within the Hogsback area in the Amathole Mountains. Nuclear and mitochondrial DNA variation was assessed using 17 microsatellite markers and by sequencing the hypervariable 1 region (HVR1). Microsatellite data generated was used to determine population structure, genetic diversity and the extent of inbreeding. Sequences of the HVR1 were used to infer individual origins, haplotype sharing and haplotype diversity. No negative genetic factors associated with isolation such as inbreeding were detected in the two groups and gene flow between groups can be regarded as fairly high primarily as a result of male migration. This was in contrast to the low nuclear genetic diversity observed (H o=0.45). A further reduction in heterozygosity may lead to inbreeding and reduced offspring fitness. Translocations and establishment of habitat corridors between forest patches are some of the recommendations that have emerged from this study which will increase long-term population viability of the subspecies.

Genetic Diversity and Inbreeding Level of Cotoneaster orbicularis Schltdl. in The Sinai Mountains Revealed by Microsatellite Markers and Flow Cytometry

COTONEASTER orbicularis Schltdl, native to Egypt and the eastern part of the Arab peninsula, is an endangered species and the surviving individuals are dispersed in the mountains of South Sinai, Egypt. Several threats, including habitat aridification and the impact of human interference have caused a noticeable reduction in population size and number. Analyzing the genetic diversity and mating system of C. orbicularis is crucial for its conservation and management. In this study, six polymorphic microsatellite markers, formerly developed as species-specific markers, were used to assess the genetic variability and extent of inbreeding in the C. orbicularis populations. Flow cytometry of seeds was used to establish genome size. Low total heterozygosity (HT = 0.464) for all loci and populations, high differentiation between populations (FST = 0.634, RST = 0.889), and high levels of inbreeding (F = 0.906) were found. Most of the embryos possessed about 1.9 pg/2C DNA; however, embryos with 3.8 pg/2C DNA also occurred. The results provide markers that can be used in the management of conservation, including habitat recovery and ex-situ conservation, in order to prevent extinction.

Important genealogical bloodlines of Pinzgau cattle in Slovakia

Received: 2016-05-26 | Accepted: 2016-06-13 | Available online: 2017-03-31 http://dx.doi.org/10.15414/afz.2017.20.01.13-15 The aim of this paper was to analyze sire bloodlines within the Slovak Pinzgau cattle population. There were 13 genealogical bloodlines found together. The most widespread bloodline was Apollo. The average estimated breeding values according to sire bloodlines were predominately negative. The best milk production EBV were found in Benito line (-39.35 kg). The best growth ability according to EBV for weaning weight (210 days) was found in Karst bloodline (+3.39 kg). Significant influence of genealogical bloodline was found on EBV for weight in 365 days, protein production and weaning weight (210 days). References ANTALIK, P. and STRAPAK, P. (2010). The evaluation of milkability of Slovak Pinzgau cattle by lactocorder. Slovak J. Anim. Sci., vol. 43, no. 4, pp. 173–178. ERHARD L. and. SCHMID, D. O. (1965). Blood Group Studies on Pinzgau-Cattle. Matousek, J. (ed). Blood Groups of Animals. Proceedings of the 9th European Animal Blood Group Conference (First Conference Arranged by E.S.A.B.R.) held in Prague, August 18–22, 1964. doi:http://dx.doi.org/10.1007/978-94-017-6289-2_5 KADLECIK, O. et al. (2004) Development of dual-purpose Pinzgau cattle. Nitra: Slovak University of Agriculture in Nitra. 128 p. KASARDA, R. and KADLECIK, O. (2007) An economic impact of inbreeding in the purebred population of Pinzgau cattle in Slovakia on milk production traits. Czech Journal of Animal Science, vol. 15, no. 1, pp. 8–13. KASARDA, R. et al. (2014) Influence of mating systems and selection intensity on the extent of inbreeding and genetic gain in the Slovak Pinzgau cattle. Czech Journal of Animal Science, vol. 59, no. 5, pp. 219–226. PAVLIK, I. et al. (2014) Joint genealogical analysis as a tool for diversity evaluation in Pinzgau cattle populations. Archiv Tierzucht, vol. 57, no. 14, pp. 1–12. SAS. (2009) User´s Guide Version 9.2. SAS/STAT ® SAS Institute Inc. Cary, NC, USA. SIDLOVA, V. et al. (2014a) Microsatellite analysis of population structure in Slovak Pinzgau cattle. Acta Agraria Kaposvarienis, vol. 18, supplement 1, pp. 24–29. SIDLOVA, V. – KASARDA, R. – MORAVCIKOVA, N. (2014b). Genealogic structure of Slovak Pinzgau cattle population. MendelNet 2014: International Scientific Conference Proceedings, Brno, November 19–20, 2014. pp. 187–191.

Inbreeding depression and environmental effect on milk traits of the Murciano-Granadina goat breed

The extent of inbreeding as well as environmental factors such as parity order, age at kidding and contemporary group (herd-year-season) was evaluated for their effects on the total production of milk, fat, protein and dry extract in Murciano-Granadina goats in Spain. The pedigrees of 11,926 females were traced to calculate the inbreeding coefficient for each animal. The lactations of these 22,832 females were analysed, standardised to 210 days of lactation, and information on the whole milk, fat, protein and dry extract production was recorded. The least squares method was used, and fixed effects in the model included parity order, the age of goat at kidding and contemporary group, and the inbreeding rate as a continuous variable, considering linear and quadratic effects. Based on this model, only 1.18% of the animals presented inbreeding, and the average population was of low magnitude (0.24%). However, among inbred animals, the average was considered high (20.31%). The total average of milk, fat, protein and dry extract production is within the range considered normal for the breed. The variables of parity order, the age of goat at kidding and contemporary group, exerted a statistically significant influence on the milk production and composition traits. Inbreeding had a quadratic effect on total milk production with a minimum point at 10.59% of inbreeding. Inbreeding had a positive linear correlation with total fat and dry extract yield. There was no statistically significant effect of inbreeding on total protein production. In general, the inbreeding levels in the Murciano-Granadina goat population did not negatively affect milk traits in the evaluated period.

Influence of mating systems and selection intensity on the extent of inbreeding and genetic gain in the Slovak Pinzgau cattle

The aim of the present paper was to simulate the scenarios for a maximum avoidance of inbreeding (MAI) mating strategy, and compare it with a random mating alternative, with the main focus on inbreeding and development of the genetic gain. The parameters of the simulation were based on the structure of the Slovak Pinzgau active population of 2868 animals (930 purebred cows). The selection under a total merit index (TMI) was simulated, covering the milk, survival, and live weight breeding value estimation results. The heritability of TMI (h&lt;sup&gt;2&lt;/sup&gt; = 0.09) was estimated using a REML single trait animal model. Alternatives assumed a closed population structure, fixed number of mating per parent, and equal use of sires in insemination. Animals in generation 0 were set as founders without pedigree information. In separate simulation runs, the number of sires of sires was set at 2, 4, 5 or 10 mated with 40 dams of sires in all cases. The sex ratio of the offspring was assumed to be 50/50 male/female. Twenty consecutive generations were simulated for both random and maximum avoidance of inbreeding mating, which resulted in a total of 8 scenarios. Significant positive differences in genetic gain were observed in the MAI mating system with 2 (0.74**), 4 (0.24**), 5 (0.13**) or 10 (0.09**) sires in comparison to random mating design. When using MAI, significantly lower inbreeding was observed with 2&amp;nbsp;(5.44**), 4 (3.18**), 5 (2.43**) or 10 (1.16**) sires. Simulation results showed that the use of a maximum avoidance of inbreeding mating strategy would lead to significantly decreased rates of inbreeding while maintaining suitable levels of genetic gain in the

A Heterogeneous Strategy Genetic Algorithm and its Application in Dynamic Optimization of Structure

Heterogeneous strategy is used to improve genetic algorithm. It can increase the population diversity and avoid premature while the convergence efficiency is ensured. Furthermore, an expression to estimate the extent of inbreeding and two methods for selecting heterogeneity were given, and, an improved generalized genetic algorithm was presented in this paper. This algorithm is used for multi-parameter dynamic optimization of the structure which is under random loads and has stress constrains. Numerical examples demonstrated that heterogeneous strategy can improve the probability of convergence to global optimal solution and the improved generalized genetic.

Colorectal cancer risk is not associated with increased levels of homozygosity in Saudi Arabia

Purpose:Runs of homozygosity (ROHs) represent a measure of the extent of autozygosity and are correlated with the extent of inbreeding. Recently, it has been suggested that ROHs may contribute to the risk of colorectal cancer (CRC). The high rate of consanguinity and CRC in the Saudi population prompted us to test the role of autozygosity in the CRC risk.Methods:We compared 48 Saudi CRC patients to 100 ethnically matched controls, processed on the Affymetrix 250K StyI SNP GeneChip platform and analyzed using the plink package.Results:We could find no evidence of a significant relationship between autozygosity and CRC risk.Conclusion:The negative results in our study add additional significance to what has been previously reported in literature, as this is the first study to address these questions in an inbred population. Our subgroup analysis of patients with microsatellite unstable-positive tumors as compared with other groups did not significantly change our results. Although these results do not rule out the presence of recessively acting CRC-predisposing genes in a small percentage of patients, which our relatively small sample size could not capture, they suggest that such genes are unlikely to account for the disturbingly high incidence of CRC in our consanguineous population.Genet Med advance online publication 5 April 2012.

Abstract 3768: Colorectal cancer risk is not associated with increased levels of homozygosity in a population from Saudi Arabia

Abstract Autozygosity is a term used to denote the presence of two identical haplotypes that are derived from an ancestor shared by both parents, so it essentially represents a special type of homozygosity. Runs of homozygosity (ROH) in the genome is a measure of the extent of autozygosity and is directly correlated with the extent of inbreeding. While the role of ROH in unmasking recessively acting mutations is well established in Mendelian genetics, much less is known about their contribution to more complex disorders such as cancer. Recently, it has been suggested that ROH may contribute to the risk of colorectal cancer (CRC) perhaps through the unmasking of a recessively acting CRC-predisposing mutations in one or more genes. However, this observation could not be replicated. In this study, we examine the role of homozygosity in the CRC risk by asking four specific questions. First, do CRC patients have enrichment for ROH in particular chromosomal regions compared to controls? Second, do CRC patients have longer ROH compared to controls? Third, is there a particular SNP that is more likely to be homozygous in CRC patients compared to controls? And fourth, are CRC patients more inbred than controls? By comparing 48 Saudi CRC patients to 100 ethnically matched controls, all processed on Affy 250SytI SNP Chip platform and analyzed by Partek, we found that the answer is no to all these four questions. We note here that this is the first study to address these questions in an inbred population so the negative results in our study carry more significance than what has been previously reported in the literature. We also note that our subgroup analysis of patients with MSI-positive tumors compared to other groups did not significantly change our results. While these results do not rule out the potential presence of recessively acting CRC-predisposing genes in a small percentage of patients that our relatively small sample size could not capture, they do suggest that such genes are unlikely to account for the disturbingly high incidence of CRC in our consanguineous population and that future research should consider other mechanisms. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3768. doi:10.1158/1538-7445.AM2011-3768

High clonal diversity in threatened peripheral populations of the yellow bird's nest (Hypopitys monotropa; syn. Monotropa hypopitys).

Peripheral populations of plant species are often characterized by low levels of genetic diversity as a result of genetic drift, restricted gene flow, inbreeding and asexual reproduction. These effects can be exacerbated where range-edge populations are fragmented. The main aim of the present study was to assess the levels of genetic diversity in remnant populations of Hypopitys monotropa (syn. Monotropa hypopitys; yellow bird's nest) at the edge of the species' European range in Northern Ireland, since these remnant populations are small and highly fragmented. Every plant found through surveys of 21 extant populations was genotyped for eight microsatellite loci to estimate levels and patterns of genetic diversity and clonality. Levels of genetic diversity were relatively high in the populations studied, and the incidence of clonal reproduction was generally low, with a mean of only 14·45 % of clonal individuals. Clones were small and highly spatially structured. Levels of inbreeding, however, were high. The observed low levels of clonality suggest that the majority of genets in the populations of H. monotropa studied are fertile and that reproduction is predominantly sexual. As the species is highly self-compatible, it is likely that the high levels of inbreeding observed in the populations in the present study are the result of self-pollination, particularly given the small numbers of individuals in most of the patches. Given this extent of inbreeding, further genetic monitoring would be advisable to ensure that genetic diversity is maintained.

Population structure of Plasmodium falciparum gametocyte sex ratios in malarious children in an endemic area

The gametocyte sex ratio (proportion of gametocytes that are male) of Plasmodium falciparum may influence transmission. The distribution of P. falciparum sex ratios, the extent of inbreeding, the relationship between clone multiplicity and sex ratio, and the pre- and post-treatment factors influencing a sex ratio of 0.5 were determined in 1609 children, with acute malaria. Gametocytes were sexed by morphological appearance and asexual clone multiplicity was determined by polymerase chain reaction (PCR) using polymorphic loci of merozoite surface proteins-1 and -2 (MSP-1, MSP-2) and glutamine-rich protein (GLURP). The weighted mean population sex ratio on presentation in 162 gametocyte carriers was 0.22, that is, 3.5 female to 1 male (95% CI 0.15–0.28), with an estimated inbreeding rate (f) (the proportion of a mother's daughters that is fertilized by her sons) of 0.56 (95% CI 0.44–0.70). Sex ratio was significantly higher when clone multiplicity was >1 infecting clone than when it was 1 (P=0.02). The frequency of a pre-treatment sex ratio of 0.5 was low (3%), and was significantly increased by non-artemisinin but not by artemisinin – mono or combination – drugs by day 7 after therapy commenced (P=0.03 and P=0.44, respectively). No factor was associated with a pre-treatment sex ratio of 0.5 but two factors were independent predictors of a sex ratio of 0.5 by day 7 after therapy commenced: an age ≥5years and anaemia. These population data provide some empirical support for the predictions of local mate competition (LMC) theory and, in conjunction with effects of antimalarials on a sex ratio of 0.5, may have implications for malaria control efforts in endemic settings.

Heritabilities, apolipoprotein E, and effects of inbreeding on plasma lipids in a genetically isolated population: the Erasmus Rucphen Family Study.

Despite considerable progress in unravelling the genetic basis of dyslipidemias, most findings are based on families with extreme phenotypes. We studied lipid levels in an extended pedigree ascertained irrespective of phenotype from the population of a recent genetic isolate in the Netherlands. Heritabilities of plasma lipid measures were examined; this analysis also included estimates of the proportion of variance attributable to ApoE genotype. The association between inbreeding and lipids was also considered, as a substantial fraction of the population had known inbreeding. A total of 868 individuals from this pedigree, containing more than 60,000 people over 15 generations, were investigated in this study. Laboratory analysis of these subjects included the determination of fasting plasma lipids. ApoE ɛ2/3/4 status was ascertained using TaqMan assays. Heritabilities for plasma lipids were estimated with adjustments for multiple covariates using SOLAR. Heritabilities for total cholesterol (TC), high-density lipoprotein cholesterol (HDL), low-density lipoprotein cholesterol (LDL), triglycerides (TG), TC/HDL ratio, and TG/HDL ratio were found to be 0.35, 0.56, 0.30, 0.24, 0.49, and 0.39, respectively. The addition of ApoE genotype in the model significantly decreased these estimates (Δh2 = −0.030, −0.004, −0.054, and −0.006 for TC, HDL, LDL, and TG). In a further analysis, TC and LDL were positively associated with the extent of inbreeding (ptrend = 0.02 and ptrend = 0.05, respectively). These data provide estimates of lipid heritability unbiased due to selection and suggest that this population represents a good opportunity to localize novel genes influencing plasma lipid levels.

Native breeds demonstrate high contributions to the molecular variation in northern European sheep

Population contribution to genetic diversity can be estimated using neutral variation. However, population expansion or hybridization of diverged ancestries may weaken correlation between neutral and non-neutral variation. Microsatellite variation was studied at 25 loci in 20 native and 12 modern or imported northern European sheep breeds. Breed contributions to total gene diversity, allelic richness and mean allele-sharing distance between individuals were measured. Indications of changes in population size and admixtures of divergent ancestries were investigated and the extent of inbreeding was estimated. The northern European sheep demonstrated signs of reduction in effective population size. Many old, small populations made a substantial positive contribution to total molecular variation, but populations with several divergent major ancestries did not contribute substantially to molecular variation, with the exception of the Norwegian Rygja sheep. However, several diverged major ancestries may cause it to contribute less to non-neutral variation than expected from the microsatellite data. Breed uniqueness and within-breed variability generally had opposite effects on breed contributions to molecular diversity. The degree of inbreeding did not reflect the breed contribution to total gene diversity or allelic richness, but inbred populations increased the mean allele-sharing distance between individuals. Our study indicates breed conservation to be especially important in maintaining allelic variation in northern European sheep and supports the evolutionary importance of peripheral populations.

Genetic diversity in wild wheats and goat grass

The genetic structure of 35 populations of wild relatives of cultivated wheats, all collected in Syria and Lebanon, was assessed using ten isozymes. The populations consisted of diploid goat grass, Aegilops speltoides, diploid wild wheats, Triticum monococcum spp. aegilopoides and T. urartu, and tetraploid wild wheat, T. turgidum ssp. dicoccoides. The majority of the populations were polymorphic (P=0–70%) having low within-population mean genetic diversity (Hep=0.05–0.10) and relatively high within-species genetic diversity (Hes=0.14–0.31). The linkage between loci did not seem to be one of the causes for the observed polymorphism. All four species showed significant inbreeding at both the population (0.31–0.64) and species (0.77–0.96) levels, and the extent of inbreeding did not correlate with mating systems. Despite their apparent common ecological and evolutionary history, between-population or between-species level genetic identity was low (I=0.43–0.86). Among the diploid species, populations of Ae. speltoides clustered distinctly from those overlapping clusters of T. monococcum ssp. aegilopoides and T. urartu. The tetraploid species T. turgidum ssp. dicoccoides had relatively less genetic diversity (Hes=0.14) and was highly homozygous (F=0.96). The results suggest that these wild progenitors of cultivated wheats have undergone extensive local differentiation and inbreeding. We discuss the implications of our results on the management of wild wheat and goat grass populations.

Testing for inbreeding and outbreeding depression in the endangered Gila topminnow

AbstractThe extent of inbreeding and outbreeding depression is thought to be a fundamental factor influencing the long term persistence of an endangered species. However, there have been no comprehensive examinations of either factor in an endangered species, except for a mouse species. Here we examined both the extent of inbreeding and outbreeding depression for five traits related to fitness in populations from the four watersheds in which the endangered Gila topminnow (Poeciliopsis o. occidentalis) still exists in the USA by making experimental matings with replicate samples and simultaneous controls. There was generally high survival, similar body size, and little bilateral asymmetry for all the inbred and outbred matings for all populations, i.e. there was no evidence of either inbreeding or outbreeding depression for these traits. Similarly there was no evidence of inbreeding or outbreeding effects for fecundity or sex ratio except for the sample from Monkey Spring, which had highly skewed (female‐biased) sex ratios after one generation of inbreeding. In addition, brood sizes for Sharp Spring declined over time in inbred lines maintained by full‐sib mating. These results further support the suggestion, based on molecular genetic analysis and considerations of habitat differences, that Monkey Spring be considered an evolutionarily significant unit, distinct from the remainder of existing populations. Potential explanations for the results and their implications for conservation are discussed.

Testing for inbreeding and outbreeding depression in the endangered Gila topminnow

The extent of inbreeding and outbreeding depression is thought to be a fundamental factor influencing the long term persistence of an endangered species. However, there have been no comprehensive examinations of either factor in an endangered species, except for a mouse species. Here we examined both the extent of inbreeding and outbreeding depression for five traits related to fitness in populations from the four watersheds in which the endangered Gila topminnow (Poeciliopsis o. occidentalis) still exists in the USA by making experimental matings with replicate samples and simultaneous controls. There was generally high survival, similar body size, and little bilateral asymmetry for all the inbred and outbred matings for all populations, i.e. there was no evidence of either inbreeding or outbreeding depression for these traits. Similarly there was no evidence of inbreeding or outbreeding effects for fecundity or sex ratio except for the sample from Monkey Spring, which had highly skewed (female-biased) sex ratios after one generation of inbreeding. In addition, brood sizes for Sharp Spring declined over time in inbred lines maintained by full-sib mating. These results further support the suggestion, based on molecular genetic analysis and considerations of habitat differences, that Monkey Spring be considered an evolutionarily significant unit, distinct from the remainder of existing populations. Potential explanations for the results and their implications for conservation are discussed.