http://jhered.oxfordjournals.org Journal of Heredity - RSS feed of current issue 1465-7333 September-October 2008 Journal of Heredity 0022-1503 http://jhered.oxfordjournals.org/cgi/content/short/99/5/443?rss=1 We investigated population genetic structure and regional differentiation among African savannah elephants in Kenya using mitochondrial and microsatellite markers. We observed mitochondrial DNA (mtDNA) nucleotide diversity of 1.68% and microsatellite variation in terms of average number of alleles, expected and observed heterozygosities in the total study population of 10.20, 0.75, and 0.69, respectively. Hierarchical analysis of molecular variance of mtDNA variation revealed significant differentiation among the 3 geographical regions studied (F_CT = 0.264; P < 0.05) and a relatively lower differentiation among populations within regions (F_SC = 0.218; P < 0.0001). Microsatellite variation significantly differentiated among populations within regions (F_SC = 0.019; P < 0.0001) but not at the regional levels (F_CT = 0.000; P > 0.500). We attribute the high differentiation at the mitochondrial genome to the matrilineal social structure of elephant populations, female natal philopatry, and probably ancient vicariance. Lack of significant regional differentiation at the nuclear loci vis-a-vis strong differences at mtDNA loci between regions is likely the effect of subsequent homogenization through male-mediated gene flow. Our results depicting 3 broad regional mtDNA groups and the observed population genetic differentiation as well as connectivity patterns should be incorporated in the planning of future management activities such as translocations.

]]> 2008-08-06 info:doi/10.1093/jhered/esn028 American Genetic Association 5 99 452 2008-09-01 443 Articles http://jhered.oxfordjournals.org/cgi/content/short/99/5/453?rss=1 Genetic analyses for many widespread North American species have revealed significant east–west differentiation, indicating that many survived through the Pleistocene in 2 glacial refugia—1 in the eastern and 1 in the western part of the continent. It remains unclear, however, whether other areas may have served as important glacial refugia. Moreover, many such species exhibit widespread genetic similarity within eastern and western regions because of recent expansion from small refugial populations, making it difficult to evaluate current-day levels of gene flow. In this study, we used mitochondrial DNA (mtDNA) control region sequence and amplified fragment length polymorphism markers to survey genetic variation in a widespread migratory bird, the American redstart (Setophaga ruticilla). mtDNA analyses revealed a pattern that contrasts with that found for most other widespread species studied to date: most redstart populations across North America appear to have spread out from a single glacial refugium, possibly located in the southeastern United States, whereas populations in far-eastern Canada may have survived in a second glacial refugium located on the now-submerged Atlantic coastal shelf off the coast of Newfoundland. A pattern of isolation by distance in mtDNA suggested some constraints on current-day gene flow among extant redstart populations. This study thus reveals a recent evolutionary history for this species that differs from that of most other widespread North American passerines and provides evidence for limited gene flow in a species with potentially large dispersal distances.

]]> 2008-08-06 info:doi/10.1093/jhered/esn025 American Genetic Association 5 99 463 2008-09-01 453 Articles http://jhered.oxfordjournals.org/cgi/content/short/99/5/464?rss=1 Phylogenetic, population, and coalescent methods were used to examine the genetic structuring of Pachysoma gariepinum, a flightless dung beetle species endemic to the arid west coast of southern Africa that exhibits interrupted south to north morphological clinal variation along a distributional gradient. Mitochondrial cytochrome oxidase I sequence data of 67 individuals from 5 localities revealed the presence of 3 geographically distinct evolutionary lineages (with an overall nucleotide divergence of 5.7% and a per-locality divergence of 1.9–3.8%) which display significant levels of genetic structuring. The separation of the lineages was estimated to have occurred between 2.2 and 5.7 million years ago—which is the late Miocene, early Plio-Pleistocene era—possibly in response to the ebb and flow of the Orange and Holgat River systems as well as the interactions between the moving and stable sand dune systems. Moreover the species’ current range appears to have been influenced by the formation of advective fog resulting in a constant source of water in an area with low precipitation thereby allowing for the beetles to radiate to areas that were previously inhospitable. Fu's F-statistics and population parameters based on recent mutations indicated that little to no recent population growth has occurred. This together with changing anthropogenic factors and the recovery of 3 geographically discrete management units, points to a need for census data in order to monitor and conserve the genetic diversity of this species.

]]> 2008-08-06 info:doi/10.1093/jhered/esn046 American Genetic Association 5 99 475 2008-09-01 464 Articles http://jhered.oxfordjournals.org/cgi/content/short/99/5/476?rss=1 A comparative study between microsatellite and allozyme markers was conducted on the genetic structure and mating system in natural populations of Euterpe edulis Mart. Three cohorts, including seedlings, saplings, and adults, were examined in 4 populations using 10 allozyme loci and 10 microsatellite loci. As expected, microsatellite markers had a much higher degree of polymorphism than allozymes, but estimates of multilocus outcrossing rate ( = 1.00), as well as estimates of genetic structure (F_IS, G_ST), were similar for the 2 sets of markers. Estimates of R_ST, for microsatellites, were higher than those of G_ST, but results of both statistics revealed a close agreement for the genetic structure of the species. This study provides support for the important conclusion that allozymes are still useful and reliable markers to estimate population genetic parameters. Effects of sample size on estimates from hypervariable loci are also discussed in this paper.

]]> 2008-08-06 info:doi/10.1093/jhered/esn055 American Genetic Association 5 99 482 2008-09-01 476 Articles http://jhered.oxfordjournals.org/cgi/content/short/99/5/483?rss=1 Fluorescence in situ hybridization (FISH) was used to identify the X and Y chromosomes of offspring produced by normal and "apparent" XY-female fall-run Chinook salmon (Oncorhynchus tshawytscha) from California. FISH experiments were performed using probes to 2 sex-linked loci, growth hormone pseudogene (GH-), and OtY1, as well as a probe to a sex-linked microsatellite (Omy7INRA). Comparison of FISH staining patterns between the offspring produced by normal and apparent XY-females revealed that the apparent XY-female examined transmitted a "Y-like" chromosome with an attenuated OtY1 and GH- signal to half of its offspring. Segregation analysis of microsatellites derived from rainbow trout (Oncorhynchus mykiss) with respect to phenotypic sex was carried out for 2 normal and 2 apparent XY-female Chinook salmon families. Inheritance patterns of Omy7INRA were consistent with this locus being closely linked to GH- in males and in apparent XY-females carrying the Y-like chromosome. Another microsatellite locus (Omm1077) was closely linked to the primary sex-determining locus (SEX) in males but not to GH-/OtY1 in apparent XY-females. The FISH analyses suggest that apparent XY-female fall-run Chinook salmon in California are not the product of a Y chromosome to autosome translocation. Despite the combined FISH and inheritance analyses, we were unable to differentiate between 2 alternative explanations for apparent XY-females, namely, recombination of markers between the sex chromosomes, or a Y chromosome with a dysfunctional or missing sex-determining region.

]]> 2008-08-06 info:doi/10.1093/jhered/esn038 American Genetic Association 5 99 490 2008-09-01 483 Articles http://jhered.oxfordjournals.org/cgi/content/short/99/5/491?rss=1 CrV1, a polydisperse DNA virus (polydnavirus or PDV) gene contributes to the suppression of host immunity in Cotesia genus parasitoids. Its molecular evolution was analyzed in relation to levels of resistance in the sympatric host species. Natural selection for nonsynonymous substitutions (positive Darwinian selection) was observed at specific amino acid sites among CrV1 variants; particularly, between parasitoid strains immune suppressive and nonimmune suppressive to the main resistant stem borer host, Busseola fusca. In Cotesia sesamiae, geographic distribution of CrV1 alleles in Kenya was correlated to the relative abundance of B. fusca. These results suggest that PDV genes evolve through natural selection and are genetically linked to factors of suppression of local host resistance. We discuss the forces driving the evolution of CrV1 and its use as a marker to understand parasitoid adaptation to host resistance in biological control.

]]> 2008-08-06 info:doi/10.1093/jhered/esn047 American Genetic Association 5 99 499 2008-09-01 491 Articles http://jhered.oxfordjournals.org/cgi/content/short/99/5/500?rss=1 Chemokine receptors (CCRs) play an essential role in the initiation of an innate immune host response. Several of these receptors have been shown to modulate the outcome of viral infections. The recent availability of complete genome sequences from a number of species provides a unique opportunity to analyze the evolution of the CCR genes. A phylogenetic analysis revealed that the CCR2 gene evolved in concert with the paralogous CCR5 gene, but not with another paralogous gene, CCR3, in the opossum, platypus, rabbit, guinea pig, cat, and rodent lineages. In addition, evidence of concerted evolution of the CCR2 and CCR5 genes was observed in chicken and lizard genomes. A unique CCR5/2 gene that originated by unequal crossing over between the CCR2 and CCR5 genes was detected in the domestic horse. The CCR2, CCR5, and CCR5/2 genes were mapped to ECA16q21 using fluorescent in situ hybridization (FISH). Single-nucleotide polymorphisms identified in the equine CCR5 gene and characterized within 5 horse breeds provide haplotype markers for future case/control studies investigating the genetic bases of horse susceptibility to infectious diseases.

]]> 2008-08-06 info:doi/10.1093/jhered/esn029 American Genetic Association 5 99 511 2008-09-01 500 Articles http://jhered.oxfordjournals.org/cgi/content/short/99/5/512?rss=1 The murine model for Turner Syndrome is the XO mouse. Unlike their human counterparts, XO mice are typically fertile, and their lack of a second sex chromosome can be transmitted from one generation to the next as an X-linked dominant trait with male lethality. The introduction of an X-linked coat-color marker (tabby) has greatly facilitated the maintenance of this useful mouse strain. XO mice can be produced in large numbers, generation after generation, and rapidly identified on the basis of their sex and coat color. Although this breeding scheme appears to be effective at the phenotype level, its utility has never been conclusively proved at the molecular or cytogenetic levels. Here, we clone and sequence the tabby deletion break point and present a multiplex polymerase chain reaction–based assay for the tabby mutation. By combining the results of this assay with whole-chromosome painting data, we demonstrate that genotype, phenotype, and karyotype all show perfect correlation in the publicly available XO breeding stock. This work lays the foundation for the use of this strain to study Turner Syndrome in particular and the X chromosome in general.

]]> 2008-08-06 info:doi/10.1093/jhered/esn027 American Genetic Association 5 99 517 2008-09-01 512 Articles http://jhered.oxfordjournals.org/cgi/content/short/99/5/518?rss=1 The outstanding sensitivity of the canine olfactory system has been acknowledged by using sniffer dogs in military and civilian service for detection of a variety of odors. It is hypothesized that the canine olfactory ability is determined by polymorphisms in olfactory receptor (OR) genes. We investigated 5 OR genes for polymorphic sites which might affect the olfactory ability of service dogs in different fields of specific substance detection. All investigated OR DNA sequences proved to have allelic variants, the majority of which lead to protein sequence alteration. Homozygous individuals at 2 gene loci significantly differed in their detection skills from other genotypes. This suggests a role of specific alleles in odor detection and a linkage between single-nucleotide polymorphism and odor recognition efficiency.

]]> 2008-08-06 info:doi/10.1093/jhered/esn057 American Genetic Association 5 99 527 2008-09-01 518 Articles http://jhered.oxfordjournals.org/cgi/content/short/99/5/528?rss=1 The genetic structure of resource populations affects the power of tests to detect associations between DNA markers and complex traits. Following a chicken interline cross (White Plymouth Rock background), we produced a multigenerational resource population based on 4 pedigreed generations. In this large sibship, 265 parents have been genotyped, and their 3317 progenies have been phenotyped for BW21, BW42, breast meat weight, fat pad weight, and egg production. We developed an approach to increase test power by imposing several ways of validation including the minimization of false-positive associations. Some of our detected associations were in agreement with QTLs previously reported in the literature. A large fraction of the 81 screened markers was found to be associated with quantitative traits. We examined 729 associations, of which 150 (21%) were significant, and of these, 54 are supported by the literature. These 54 associations were identified by 42 markers (some of which are linked to each other). This finding not only supports the results obtained in our resource population but may also give some indication about their general properties.

]]> 2008-08-06 info:doi/10.1093/jhered/esn030 American Genetic Association 5 99 538 2008-09-01 528 Articles http://jhered.oxfordjournals.org/cgi/content/short/99/5/539?rss=1 The present study was designed to determine the effects of visible mutations of large effect on developmental stability and canalization in different morphological traits, namely, sternopleural bristle number, wing length, wing to thorax ratio, ovariole number, and sex comb tooth number (SCTN) in Drosophila ananassae. We have compared the mean trait size, fluctuating asymmetry (FA) (as an index of developmental stability), and morphological variation (as an index of canalization) of different mutant strains (yellow body color, y; claret eye color, ca; plexus wing, px; spread wing, spr; ebony body and sepia eye color, e se; yellow body and claret eye color, y ca; and cardinal eye color, curled wing, and ebony body color, cd cu e) with wild-type strain. The mean trait size of all morphological traits differs significantly among the wild-type and mutant strains. The wild-type and mutant strains vary significantly for the morphological variation and also for the levels of the FA in different morphological traits. However, we have found no increase in either the variance or in the degree of FA with the increase of the mutations (except in SCTN in y mutant). The plausible reasons for the variation in wild-type and mutant strains with particular reference to developmental stability and canalization have been discussed.

]]> 2008-08-06 info:doi/10.1093/jhered/esn026 American Genetic Association 5 99 545 2008-09-01 539 Articles http://jhered.oxfordjournals.org/cgi/content/short/99/5/546?rss=1 Many endosperm traits are related to grain quality in cereal crops. Endosperm traits are mainly controlled by the endosperm genome but may be affected by the maternal genome. Studies have shown that maternal genotypic variation could greatly influence the estimation of the direct effects of quantitative trait loci (QTLs) underlying endosperm traits. In this paper, we propose methods of interval mapping of endosperm QTLs using seeds of F₂ or BC₁ (an equal mixture of F₁ x P₁ and F₁ x P₂ with F₁ as the female parent) derived from a cross between 2 pure lines (P₁ x P₂). The most significant advantage of our experimental designs is that the maternal effects do not contribute to the genetic variation of endosperm traits and therefore the direct effects of endosperm QTLs can be estimated without the influence of maternal effects. In addition, the experimental designs can greatly reduce environmental variation because a few F₁ plants grown in a small block of field will produce sufficient F₂ or BC₁ seeds for endosperm QTL analysis. Simulation studies show that the methods can efficiently detect endosperm QTLs and unbiasedly estimate their positions and effects. The BC₁ design is better than the F₂ design.

]]> 2008-08-06 info:doi/10.1093/jhered/esn049 American Genetic Association 5 99 551 2008-09-01 546 Articles http://jhered.oxfordjournals.org/cgi/content/short/99/5/552?rss=1 Sinistral and dextral snails have repeatedly evolved by left–right reversal of bilateral asymmetry as well as coiling direction. However, in most snail species, populations are fixed for either enantiomorph and laboratory breeding is difficult even if chiral variants are found. Thus, only few experimental models of chiral variation within species have been available to study the evolution of the primary asymmetry. We have established laboratory lines of enantiomorphs of the pond snail Lymnaea stagnalis starting from a wild population. Crossing experiments demonstrated that the primary asymmetry of L. stagnalis is determined by the maternal genotype at a single nuclear locus where the dextral allele is dominant to the sinistral allele. Field surveys revealed that the sinistral allele has persisted for at least 10 years, that is, about 10 generations. The frequency of the sinistral allele showed large fluctuations, reaching as frequent as 0.156 in estimate under the assumption of Hardy–Weinberg equilibrium. The frequency shifts suggest that selection against chiral reversal was not strong enough to counterbalance genetic drift in an ephemeral small pond. Because of the advantages as a model animal, enantiomorphs of L. stagnalis can be a unique system to study aspects of chirality in diverse biological disciplines.

]]> 2008-08-06 info:doi/10.1093/jhered/esn032 American Genetic Association 5 99 557 2008-09-01 552 Brief Communications http://jhered.oxfordjournals.org/cgi/content/short/99/5/558?rss=1 Pickerelweed (Pontederia cordata L.) is a diploid (2n = 2x = 16) tristylous aquatic perennial. Populations usually contain 3 floral morphs that differ reciprocally in style length and anther height (referred to as the long-, mid-, and short-styled morphs, hereafter L-, M-, and S-morphs). The floral polymorphism promotes disassortative mating among the 3 floral morphs and is maintained in populations by negative frequency-dependent selection. The objective of this study was to determine the number of loci, number of alleles, and gene action controlling floral morph in pickerelweed. Three parental lines (one each of the L-, M-, and S-morph) were used to create S₁ and F₁ populations. F₂ populations were produced through self-pollination of F₁ plants. Progeny ratios of S₁, F₁, and F₂ generations revealed that tristyly is controlled by 2 diallelic loci (S and M) with dominant gene action. The S locus is epistatic to the M locus, with the S-morph produced by plants with the dominant S allele (genotype S _ _ _). Plants with recessive alleles at the S locus were either L-morph (ssmm) or M-morph (ssM_). The results of this experiment demonstrate that the inheritance of tristyly in pickerelweed is the same as previously reported for several tristylous species in the Lythraceae and Oxalidaceae.

]]> 2008-08-06 info:doi/10.1093/jhered/esn031 American Genetic Association 5 99 563 2008-09-01 558 Brief Communications http://jhered.oxfordjournals.org/cgi/content/short/99/5/564?rss=1 In an F₂ population of 120 plants derived from a cross between 2 breeding lines with yellow ray flowers, we observed 111 plants with yellow-colored and 9 plants with lemon-colored ray flowers. The segregation pattern fits a 15:1 (²_(15:1) = 0.32, P > 0.5) ratio, suggesting that the lemon ray flower color is conditioned by 2 independent recessive genes that had been contributed individually by each of the parents. We sampled 111 plants from the 3 F_2:3 families displaying a 3 to 1 segregating ratio for genotyping with molecular markers. One of the genes, Yf₁, was mapped onto linkage group 11 of the public sunflower map. A targeted region amplified polymorphism marker (B26P17Trap13-68) had a genetic distance of 1.5 cM to Yf₁, and one simple sequence repeat marker (ORS733) and one expressed sequence tag (EST)-based marker (HT167) previously mapped to linkage group 11 were linked to Yf₁ with distances of 9.9 and 2.3 cM, respectively.

]]> 2008-08-06 info:doi/10.1093/jhered/esn033 American Genetic Association 5 99 567 2008-09-01 564 Brief Communications http://jhered.oxfordjournals.org/cgi/content/short/99/5/568?rss=1 2008-08-06 info:doi/10.1093/jhered/esn050 American Genetic Association 5 99 568 2008-09-01 568 Book Review http://jhered.oxfordjournals.org/cgi/content/short/99/5/569?rss=1 2008-08-06 info:doi/10.1093/jhered/esn059 American Genetic Association 5 99 571 2008-09-01 569 Announcements