Phosphoglucomutase electrophoretic variants in the mouse

The phosphoglucomutase (PGM) electrophoretic phenotype of the mouse (Mus musculus) consists of several distinct components which can be grouped into two major zones designated PGM-1 and PGM-2. Evidence presented here indicates that each zone is controlled by a single genetic locus denoted Pgm-1 and Pgm-2, respectively. Two variant forms segregated at the Pgm-1 locus. They were codominantly expressed and inherited as alleles at an autosomal locus. The alleles were termed Pgm-1 ^a (fast) and Pgm-1 ^b (slow). These alleles were separately fixed in a number of inbred strains of mice. Preliminary evidence based on wild mouse phenotypes indicates that variant forms also exist for PGM-2 which are inherited as alleles at an autosomal locus. Genetic linkage relationships have not been determined for these loci. PGM-1 variants and PGM-2 were expressed in mouse fibroblasts in vitro.Supported by U.S. Public Health Service grants GM-09966 and GM-07249 from General Medical Sciences and 5 F2 HD-35,531 from Child Health and Human Development; and Atomic Energy Commission contract AT(30-1)-3671.Postdoctoral Fellow of the U.S. Public Health Service.     

Gene flow in the exotic 14-spotted ladybird beetle, Propylea quatuordecimpunctata.

Propylea quatuordecimpunctata is a Palearctic ladybird beetle that has recently become established fortuitously in northeastern North America. This predator has also been cultured by the United States Department of Agriculture from geographically diverse Old World populations and propagated for release in the U.S.A. Massive releases of P. quatuordecimpunctata have not resulted in any recognized established populations, raising a number of questions about its population genetics. We sampled beetles for electrophoretic variation in three feral populations in the U.S.A., one feral population in Europe, one cultured population from Canada, and six cultured populations from the Old World. Of the 31 putative genetic loci resolved, 26 were polymorphic (84%). Mean heterozygosity was 18.32 +/- 2.84% among all loci and was 21.84 +/- 2.89% among only polymorphic loci. Cultured and feral populations showed similar levels of heterozygosity at the 11 loci scored. New World and Old World beetles showed no significant differences in heterozygosities. Wright's fixation index FST was 0.034 +/- 0.021 among feral populations and 0.331 +/- 0.101 among cultured populations. Drift was the major force driving differentiation of cultured beetle populations. Our data do not suggest that the failure of P. quatuordecimpunctata to become established in areas where it was deliberately released was related to a paucity of genie diversity. Key words : allozymes, breeding structure, biological control, gene flow, colonization.     

Enzyme polymorphism in feral, outbred and inbred rats (Rattus norvegicus).

Polymorphism at 25 loci coding for liver enzymes was studied in two feral, three outbred and three inbred rat strains by starch gel electrophoresis. No variation was found at 14 loci, and a low degree of polymorphism was detected at three. Eight loci were polymorphic in more than one population. The average degree of heterozygosity per locus per individual feral rat was 0-07. The degrees of heterozygosity observed in the outbred and inbred strains were lower, from 0-006 to 0-012. Contrary to expectation, the inbred strains were neither monomorphic nor appreciably less heterozygous than the outbred ones. The heterozygosity of the inbred strains was primarily due to two polymorphic loci, G-3-pdh and alpha-Gpdh. The reason for this polymorphism is probably the superior homeostasis of the heterozygotes.     

Genetic Diversity Within and Among Feral Populations and Domesticated Strains of the Guppy (Poecilia reticulata) in Singapore

Genetic variability within and among feral populations and cultured strains of the guppy (Poecilia reticulata) was investigated by random amplification of polymorphic DNA (RAPD) fingerprinting. Feral guppies were collected from 6 isolated populations (BT, Bukit Timah; NS, Nee Soon; TS, Tuas; MF, Mount Faber; KR, Kranji; LI, laboratory-inbred feral line), while the Tuxedo and Green Variegated strains were sampled from 2 guppy farms in Singapore. Pairwise genetic distances analyzed by unweighted pair-group method with arithmetic means revealed distinct clustering of guppy individuals into their respective populations and strains. Percentage polymorphic loci ranged from 54.96% (TS) to 68.70% (KR), while average heterozygosity ranged from 0.220 (GV) to 0.271 (KR). In contrast, TS guppies had the highest (0.850) intrapopulation genetic similarity (S), whereas KR had the lowest (0.781). Among populations and strains, S ranged from 0.703 (between GV and LI) to 0.809 (between NS and MB). The GV strain S was closer to TX (0.784) than to the feral guppies. Bootstrapped genetic distance trees depicted 3 major nodes comprising BT-TS, NS-MF, and TX-GV. Principal coordinate analysis also differentiated the 6 feral populations from the 2 cultured strains.     

Origin and genetic structure of feral rye in the western United States

Feral rye (Secale cereale) is a serious, introduced weed of dry land agricultural regions of the western United States. It closely resembles cultivated cereal rye (Secale cereale cereale L.) with the exception of having a shattering seed head. Feral rye may have originated from hybridization of cultivated rye with mountain rye, Secale strictum, as past studies of northern Californian populations suggest, or directly from volunteer cultivated rye. We characterized the genetic structure of feral rye populations across a broad geographical range and reexamined evidence for hybrid origin versus direct evolution from domesticated cultivars. Eighteen feral populations were examined from three climatically distinct regions in the western United States. Seven cultivars, four mountain rye accessions, and one wild annual relative (Secale cereale ancestrale) were included in our analysis as possible progenitors of feral rye. Individual plants were scored for 14 allozyme and three microsatellite loci. Estimates of genetic diversity in feral populations were relatively high compared to those of the possible progenitors, suggesting that the weed had not undergone a genetic bottleneck. Weed populations had no geographical structure at either a broad or a local scale, suggesting idiosyncratic colonization and gene-flow histories at each site. Feral rye populations were no more closely related to mountain rye than cultivars were. They were, however, weakly clustered as a distinct lineage relative to cultivars. Our results do not support an interspecific hybrid origin for feral rye, but do suggest that the sampled populations of feral rye share a common ancestry that may explain its weedy nature.     

Persistence of pseudorabies virus in feral swine populations

Serologic surveys for evidence of exposure to pseudorabies virus (PRV) in feral swine were conducted from November 2001 to April 2002 at 10 sites in the southeastern United States, where evidence of previous PRV exposure had been documented during 1979-89. Sera were tested in the field on the day of collection by latex agglutination. Maximum sample size per site was to be 30 animals, but sampling was discontinued before reaching this number when positive results were obtained. Positive results were obtained at all of the study sites, demonstrating long-term persistence of PRV in feral swine populations. Overall, 38 of 100 (38%) animals were positive for antibodies. Consistent results from latex agglutination tests conducted in the field and laboratory demonstrated that this test was useful as a rapid and reliable diagnostic tool when used in the field.     

Genetic control of two electrophoretic variants of glucosephosphate isomerase in the mouse (Mus musculus)

The autosomal variation and the genetic control of GPI has been determined by a comparison of electrophoretic patterns of F₁ and backcross progeny of three inbred strains of mice. The locus controlling the production of GPI in the mouse has been designated Gpi-1. Two alleles at this locus have been described and designated Gpi-1 ^a and Gpi-1 ^b, which represent, respectively, the slow and fast electrophoretic forms. Twenty-seven inbred strains of mice have been classified for these two alleles. The absence of close linkage of Gpi-1 to seven other genetic loci has been determined. It has been demonstrated that the polymorphism of Gpi-1 is widely distributed in feral mice. GPI was expressed in vitro and in four types of malignant tumors.Supported by U.S. Public Health Service Grants GM-09966, from General Medical Sciences, and GY 4193.     

Phosphoglucose isomerase gene duplication in the bony fishes: An evolutionary history

Electrophoretic patterns of phosphoglucose isomerase (PGI) in bony fishes provide strong evidence for a model of genetic control by two independent structural gene loci, most likely resulting from a gene duplication. This model is confirmed by a comparison of certain kinetic and molecular properties of the PGI homodimers (PGI-1 and PGI-2) isolated from extracts of the teleost Astyanax mexicanus. In addition, in most higher teleosts examined, the PGI enzymes show a regular pattern of tissue distribution, with PGI-2 predominant in muscle, the heterodimer often strongest in the heart, and PGI-1 predominant in liver and other organs. An examination of 53 species of bony fishes belonging to 38 families indicates a widespread occurrence of duplicate PGI loci and an early origin of the gene duplication, perhaps in the Leptolepiformes. The apparent presence of three PGI loci in trout and goldfish exemplifies how new loci can be incorporated into the genome through polyploidization.This research was supported in part by a NSF graduate traineeship to J.C.A., by the Clayton Foundation for Research in Biochemistry (G.B.K.), by NSF Grant GB-15644 and NIH Grant GM-15769 to Robert K. Selander, and by contract AT(38-1)-310 between the University of Georgia and the U.S. Atomic Energy Commission.     

Sources of genetic diversity in feral oilseed rape (Brassica napus) populations

Feral oilseed rape populations on roadsides and along other semi-natural habitats contribute to the uncertainty regarding the potential risk of transgene escape from genetically modified (GM) oilseed rape to wild or weedy populations. Knowledge about the underlying mechanism of establishment, persistence, and the evolutionary potential of feral populations is a prerequisite for a successful risk assessment and of high policy relevance. We analysed the origin, persistence, and genetic variation of feral oilseed rape populations in northwest Germany based on a field survey (2004–2007) and nuclear microsatellite markers. A maximum-likelihood approach was used to allocate individuals of feral populations to their source varieties and to hybrids between these varieties. The majority (72%) of the analysed sites was inhabited by oilseed rape for at least 2 years. The proportion of feral populations setting seeds varied between years (30–48%) and was higher than in comparable studies. Within-population genetic diversity of feral oilseed rape populations was higher than that of the common grown varieties studied. Repeated escapes of different varieties and hybridisation between these varieties were identified as the most important sources of genetic variation in feral oilseed rape populations. Up to four different source varieties were identified in feral populations. The detection of three hybrids between different varieties indicates that feral oilseed rape populations may persist via self-recruitment. Our results highlight the evolutionary potential of feral oilseed rape populations and have consequences for approaches to regulate the coexistence of genetically modified and non-GM oilseed rape varieties in the same region. Feral populations may serve as stepping stones for intraspecific and interspecific gene flow and can promote persistence of transgenes outside cultivation. The likelihood of introgressive interspecific hybridisation depends on the abundance of crossing partners, which may vary strongly from region to region.     

Rapid evolution of an established feral tilapia (Oreochromis spp.): the need to incorporate invasion science into regulatory structures

Outside of Asia exotic tilapiine fishes (Trewavas 1983) were not imported directly as native genetic resources from Africa but arrived as transits from third or fourth party sources. Founder populations of exotic tilapia species may be morphologically and meristically distinct in Africa but are still reproductively compatible due to their relatively recent divergence. As a result, feral tilapias have hybridized and introgressed in aquaculture settings before escaping to the wild. Reproductively viable hybrids have resulted, making the use of conventional systematics based upon external morphometric characterizations for species determinations useless. Microsatellite DNA marker studies of 139 tilapia from 10 locations (6 feral, 4 in culture) in southern California, USA, were conducted. Genetic similarities to a worldwide tilapia genetic database were compared by formulating a neighbor-joining dendrogram. The hypothesis that the pattern found arose by chance was tested by bootstrap resampling of 4 microsatellite loci at the 95% level of significance. A significant number of bootstrap re-samples showed that a tilapia species in aquaculture and a feral Colorado River tilapia population were 'monophyletic', meaning they originated from a single source relative to the total variation in the data. A significant number of bootstrap re-samples grouped these two populations with the reference populations of Oreochromis niloticus taken worldwide. This 'niloticus' group was found significantly distinct from a second large grouping that included all of the other California tilapia samples and a large group of O. mossambicus reference samples taken from a worldwide database. Any regulatory structure attempting to control movements of exotic tilapias based upon discerning 'species' using morphometric and meristic measurements of tilapias is inadequate. California, for example, does not permit O. niloticus for aquaculture, but the genetic signature for this species exists in feral stocks collected from the wild in California. There are likely many other places where a certain tilapia `species' are not permitted but the genetic material exists in established wild stocks within its political jurisdiction. It is recommended that a system of ecotypes (code names) based upon presence of unique DNA microsatellite markers be developed to label and regulate feral tilapia strains, and that hybrid strains be collected into a 'registry' of species based upon unique DNA markers. Such a registry could be used by regulators to better manage exotic tilapias and aquaculture developments.     

An assessment of the spatial scale of local adaptation in brown trout (Salmo trutta L.): footprints of selection at microsatellite DNA loci

Local adaptation is considered a paradigm in studies of salmonid fish populations. Yet, little is known about the geographical scale of local adaptation. Is adaptive divergence primarily evident at the scale of regions or individual populations? Also, many salmonid populations are subject to spawning intrusion by farmed conspecifics that experience selection regimes fundamentally different from wild populations. This prompts the question if adaptive differences between wild populations and hatchery strains are more pronounced than between different wild populations? We addressed these issues by analyzing variation at 74 microsatellite loci (including anonymous and expressed sequence tag- and quantitative trait locus-linked markers) in 15 anadromous wild brown trout (Salmo trutta L.) populations, representing five geographical regions, along with two lake populations and two hatchery strains used for stocking some of the populations. F_ST-based outlier tests revealed more outlier loci between different geographical regions separated by 522±228 km (mean±s.d.) than between populations within regions separated by 117±79 km (mean±s.d.). A significant association between geographical distance and number of outliers between regions was evident. There was no evidence for more outliers in comparisons involving hatchery trout, but the loci under putative selection generally were not the same as those found to be outliers between wild populations. Our study supports the notion of local adaption being increasingly important at the scale of regions as compared with individual populations, and suggests that loci involved in adaptation to captive environments are not necessarily the same as those involved in adaptive divergence among wild populations.     

Characterization of Mexican Bacillus thuringiensis strains toxic for lepidopteran and coleopteran larvae

Bacillus thuringiensis strains C-4, C-9, GM-7, and GM-10, isolated from northeast Mexico and selected for their high toxicity against lepidopteran and coleopteran pests, were characterized following United States Environmental Protection Agency (EPA)'s guidelines. Flagellar serotyping revealed that GM-7 and GM-10 belonged to serotype aizawai, whereas C-4, C-9 corresponded to the kumamotoensis serotype. GM-10 and C-9 were also shown to be the most effective against lepidoptera and coleoptera larvae, respectively. None of the tested strains produced beta-exotoxin or showed activity against mosquitoes. GM-7 and GM-10 were sensitive to R-41 and CP-51 phages. All strains synthesized crystal proteins of 130-140 kDa. PCR analysis showed that C-4, GM-7, and GM-10 strains expressed cry1 genes, and C-9 expressed cry3 and cry7/8 genes, but not cry1. However, the C-9 strain had no cross-reaction with antisera raised against Cry3A and Cry7A proteins. GM-7 and GM-10 were sensitive to R-41 and CP-51 phages. When the delta-endotoxin (crystal) from the four strains was subcutaneously injected to Balb/c mice, alone or in combination with spores, only C-4 and C-9 provoked tissue necrosis similar to that caused by the beta-exotoxin producer HD-41. Tissue necrosis was prevented with the injection of pentoxifylline, an inhibitor of tumor necrosis factor alpha (TNF-alpha) production, suggesting a role of this cytokine in the observed effect. Our results demonstrated that GM-7 and GM-10 strains are effective and suitable for control of lepidopteran pests and safe for mammals under EPA regulations. The potential of the C-9 strain for the control of several coleopteran pests, and the induction of tissue necrosis in mice by C-4 and C-9 strains, are discussed.     

Selective sweeps reveal candidate genes for adaptation to drought and salt tolerance in common sunflower, Helianthus annuus

Here we report the results of an analysis of variation at 128 EST-based microsatellites in wild Helianthus annuus, using populations from the species' typical plains habitat in Kansas and Colorado, as well as two arid desert and two distinct brackish marsh areas in Utah. The test statistics lnRV and lnRH were used to find regions of the genome that were significantly less variable in one population relative to the others and thus are likely to contain genes under selection. A small but detectable percentage (1.5-6%) of genes showed evidence for selection from both statistics in any particular environment, and a total of 17 loci showed evidence of selection in at least one environment. Distance-based measures provided additional evidence of selection for 15 of the 17 loci. Global F(ST)-values were significantly higher for candidate loci, as expected under divergent selection. However, pairwise F(ST)-values were lower for populations that shared a selective sweep. Moreover, while spatially separated populations undergoing similar selective pressures showed evidence of divergence at some loci, they evolved in concert at other loci. Thus, this study illustrates how selective sweeps might contribute both to the integration of conspecific populations and to the differentiation of races or species.     

Population genetics of Great Basin feral horses

The genetic make-up of Great Basin wild (feral) horses was investigated by blood typing studies. Blood samples of 975 feral horses from seven trap sites in Nevada and Oregon were tested by serological and electrophoretic techniques for genetic markers at 19 polymorphic loci. The average number of variants for the seven feral populations [72·1 ± 3·2 (SEM), range 62–85] was not significantly different from that of 16 domestic breeds (75·0 ± 11·5, range 58–105). The expected average frequency of heterozygotes per locus (average heterozygosity) for the feral populations (0·402 ± 0·009, range 0·368–0·442) was not significantly different from the domestic breeds (0·389 ± 0·045, range 0·295–0·443). Dendrograms constructed using pairwise comparisons of Nei's distance measurements substantiated anecdotal accounts of the origins of Great Basin horses from Iberian, American saddle horse and draft horse breeds.     

Cloning and characterization of microsatellite loci in channel catfish, Ictalurus punctatus

Short tandem repeat (microsatellite) loci were cloned from the channel catfish, Ictalurus punctatus , genome for use as molecular markers for genetic improvement of this important agricultural species. Plasmid clones containing catfish genomic DNA inserts were identified, by hybridization with tandem repeat DNA probes, and sequenced using automated laser fluorescence. A feral population of catfish displayed levels of heterozygosity greater than 0·7 for 13 of 22 loci and heterozygosity greater than 0·5 for 20 of 22 loci. Allelic polymorphism ranged from three to 17 alleles per locus in the feral population. Populations of domestic, farm-raised catfish and a research strain displayed levels of heterozygosity similar to the feral population. Non-invasive tissue sampling provided abundant material for the polymerase chain reaction-based genotype assay. The microsatellite loci will be useful in the molecular characterization and genetic improvement of channel catfish populations.     

A microsatellite analysis of five Colonial Spanish horse populations of the southeastern United States

The domestic horse (Equus caballus) was re-introduced to the Americas by Spanish explorers. Although horses from other parts of Europe were subsequently introduced, some New World populations maintain characteristics ascribed to their Spanish heritage. The southeastern United States has a history of Spanish invasion and settlement, and this influence on local feral horse populations includes two feral-recaptured breeds: the Florida Cracker and the Marsh Tacky, both of which are classified as Colonial Spanish horses. The feral Banker horses found on islands off the coast of North Carolina, which include, among others, the Shackleford Banks, the Corolla and the Ocracoke, are also Colonial Spanish horses. Herein we analyse 15 microsatellite loci from 532 feral and 2583 domestic horses in order to compare the genetic variation of these five Colonial Spanish Horse populations to 40 modern horse breeds. We find that the Corolla horse has very low heterozygosity and that both the Corolla and Ocracoke populations have a low mean number of alleles. We also find that the Florida Cracker population has a heterozygosity deficit. In addition, we find evidence of similarity of the Shackleford Banks, Marsh Tacky and Florida Cracker populations to New World Iberian horse breeds, while the origins of the other two populations are less clear.     

Occurrence of alfalfa (<Emphasis Type="Italic">Medicago sativa</Emphasis> L.) populations along roadsides in southern Manitoba,Canada and their potential role in intraspecific gene flow

Alfalfa is a highly outcrossing perennial species that can be noticed in roadsides as feral populations. There remains little information available on the extent of feral alfalfa populations in western Canadian prairies and their role in gene flow. The main objectives of this study were (a) to document the occurrence of feral alfalfa populations, and (b) to estimate the levels of outcrossing facilitated by feral populations. A roadside survey confirmed widespread occurrence of feral alfalfa populations, particularly in alfalfa growing regions. The feral populations were dynamic and their frequency ranged from 0.2 to 1.7 populations km⁻¹. In many cases, the nearest feral alfalfa population from alfalfa production field was located within a distance sufficient for outcrossing in alfalfa. The gene flow study confirmed that genes can move back and forth between feral and cultivated alfalfa populations. In this study, the estimated outcrossing levels were 62% (seed fields to feral), 78% (feral to seed fields), 82% (hay fields to feral) and 85% (feral to feral). Overall, the results show that feral alfalfa plants are prevalent in alfalfa producing regions in western Canada and they can serve as bridges for gene flow at landscape level. Management of feral populations should be considered, if gene flow is a concern. Emphasis on preventing seed spill/escapes and intentional roadside planting of alfalfa cultivars will be particularly helpful. Further, realistic and pragmatic threshold levels should be established for markets sensitive to the presence of GE traits.     

A profile of Drosophila species' enzymes assayed by electrophoresis. I. Number of alleles,heterozygosities, and linkage disequilibrium in glucose-metabolizing systems and some other enzymes

Seven isolated large populations of Drosophila belonging to five different species were examined by starch gel electrophoresis for allozyme variation. Six to eleven enzyme loci in the glucose-metabolizing system (group I) and six to eight enzyme loci (group II) which were not directly involved in the above-mentioned system were assayed. The parameters estimated were the average number of alleles per locus, allele frequencies, proportions of polymorphic loci, and average heterozygosity per population for group I and group II loci. The major finding is that genetic variability measured by allozyme variations is much higher for group II than for group I enzymes in terms of every parameter in all the populations. This is consistent with the earlier findings in D. ananassae by Gillespie and Kojima (1968). Linkage disequilibrium, a measure of genome integration, was computed between an enzyme locus and an inversion segment of the same chromosome. The preliminary analysis of this aspect of the study indicates that no substantial linkage disequilibrium builds up between the chromosomal segments unless the pair of segments is less than 10 centimorgan units apart.This study was supported by USPHS Grant GM-15769 and Atomic Energy Commission Contract AT-(40-1)-3681.NIH Trainee supported by Grant 5 TO 1 GM 00337.     

Gene Differences between the Sex Ratio and Standard Gene Arrangements of the X Chromosome and Linkage Disequilibrium between Loci in the Standard Gene Arrangement of the X Chromosome in DROSOPHILA PSEUDOOBSCURA

The Standard and Sex Ratio gene arrangements of the X chromosome of D. pseudobscura differ from each other in allele frequencies at the four X chromosome loci, esterase-5, adult acid phosphatase-6, phosphoglucomutase-1 and octanol dehydrogenase-3. The Standard arrangement which is the common arrangement in all populations is polymorphic at these loci in varying degrees, the geographically less widespread Sex Ratio arrangement has little polymorphism and is genically predominantly E-5(1.04) AP-6(-) Pgm1(1.0) ODH-3(1.0). The Sex Ratio arrangement from different populations is alike at all of the four loci, the Standard arrangement shows some gene frequency differences among populations. The Standard and Sex Ratio arrangements differ from each other by three inversions which suggests that the two arrangements are "old". Gene differences between these two chromosome arrangements can be explained due to differential natural selection of alleles in the Standard and Sex Ratio arrangments.-The order and percent recombination among these four loci in the Standard arrangement are: E-5-.294-AP-6-.335-Pgm-1-.024-ODH-3. The Standard X chromosomes from four different wild populations were analyzed for evidence of linkage disequilibrium between pairs of loci at these four loci. No evidence of linkage disequilibrium between pairs of loci was obtained. However, when linkages involving simultaneously three loci, E-5, AP-6 and Pgm-1 are considered, then significant departure from linkage equilibrium is observed.     

Gene flow from cultivated to wild raspberries in Scotland: developing a basis for risk assessment for testing and deployment of transgenic cultivars

In order to help establish a basis for assessing the risk associated with the testing and large-scale deploymen of transgenic raspberries, wild and feral raspberry populations in Scotland were surveyed for evidence of the escape of genes introduced into raspberry cultivars by traditional breeding. The genes concerned were introduced into cultivars using traditional breeding techniques and were deployed at known times 20 to 30 years prior to the present survey. Escape of the semidominant L ₁ gene, affecting fruit size and plant morphology, could not be detected after 30 years in test plots at the Scottish Crop Research Institute near Dundee. The recessive gene s, conferring spinelessness, was detected at very low frequencies (estimated at 0.004) in wild populations within the commercial production locales where cultivars carrying this gene had been introduced on a large scale beginning 21-years prior to this survey. This gene was not, however, found in any areas remote from the commercial production locales. The results of the survey indicate that escape does occur following large-scale deployment but that gene flow events are probably infrequent and spread is localized for genes having probable neutral selective value.