Allozyme Phenotypes Research Articles

Phenotypic Changes in Populations ofPhytophthora infestansfrom Eastern Germany

A total of 106 isolates of Phytophthora infestans collected in eastern Germany between 1976 and 1990 was analyzed for mating type, allozyme phenotype, and response to metalaxyl. The A2 mating type was found among isolates collected in 1980. Although an increase in the frequency of the A2 mating type has been observed since 1976, it did not increase to a frequency of 0.5, which is found in Mexico. Metalaxyl resistance was first observed among isolates collected in 1977, prior to the commercial use of the fungicide in eastern Germany. Between 1976 and 1990 the frequency of isolates resistant within a sample to metalaxyl increased from 0 to 40% []

Associations between allozyme phenotypes and soil nutrients in a natural population of jack pines ( Pinus banksiana)

In order to investigate potential selective forces underlying the observed allozyme polymorphisms in plant natural populations, associations between phenotypes of 14 allozymes at 11 loci encoding eight enzyme systems and 16 soil nutrients in a natural population of jack pine ( Pinus banksiana Lamb.) were examined by canonical correlation and multiple linear regression analyses. Results indicate that there is no significant overall association between the two sets of variables. However, two allozyme alleles, Ald1–2 and Aph-1, were found to be significantly associated with soil nutrients. Ald1–2 appeared more often in soils with high concentrations of K and low concentrations of Si and Ti, while the allozyme encoded by Aph-1 was positively associated with the concentration of heavy metal ions in the soil solution. Results from analysis of variance demonstrate that the concentrations of heavy metal ions in the soil solution of the two groups of trees, i.e. trees with and without Aph-1, were significantly different. Utilizing physiological information on APH enzymes and similar patterns evidenced in other species, we conclude that the APH allozyme encoded by Aph-1 in jack pine may enhance fitness where there are elevated concentrations of heavy metal ions in the soil solution.

Peroxidase Allozyme Phenotypes in Castanea and Their Segregation among Progeny

Peroxidase Allozyme Phenotypes in Castanea and Their Segregation among Progeny

Mating systems of Cuphea laminuligera and Cuphea lutea

In this paper, the mating systems of experimental populations of C. laminuligera and C. lutea are described. Outcrossing rates (t) were estimated for four populations of C. laminuligera and three populations of C. lutea using allozyme phenotypes of open-pollinated individual plant families. Populations were grown at densities of 1.0 × 1.0 m (low) and 0.04 × 0.3 m (high). Pollen and ovule frequencies and single locus and multilocus outcrossing rates were estimated for each population using the mixed-mating model. Multilocus estimates of t ranged from 0.83 to 0.98 and 1.00 to 1.01 for low and high density populations of C. laminuligera, respectively, and 0.17 to 0.26 and 0.36 to 0.54 for low and high density populations of C. lutea, respectively. C. laminuligera is predominantly allogamous; however, selfing rates as great as 17% were observed for this species. C. lutea is predominantly autogamous, but outcrossing rates as great as 54% were observed for this species. Outcrossing rates increased as density increased within C. lutea populations.

Genotypic diversity of asexual Ostracoda from a low arctic site

AbstractThe crustacean subclass Ostracoda shows an exceptionally high incidence of transitions from sexual to asexual reproduction, whose cause remains uncertain. In the current study, patterns of allozymic variation were examined in 12 species of asexual ostracodes at a low arctic site. Populations of 11 species had genotypic frequencies consistent with apomixis, having gross departures from Hardy‐Weinberg expectations and non‐random associations between loci. Allozyme phenotypes suggest that polyploidy is common in most asexual ostracode species in arctic ponds. Although most species had low clonal diversity, 3 had unusually high diversity, with a maximum of 18 clones detected per pond. Asexual species belonging to genera with sexual relatives had higher clonal diversities than those from genera without sexuals, suggesting that sexuals may serve as the source of this clonal diversity.

GENETIC DIFFERENTIATION AND HYBRIDIZATION BETWEEN CAREX GYNODYNAMA AND C. MENDOCINENSIS (CYPERACEAE) IN CALIFORNIA

Patterns of variation within and between Carex gynodynama and C. mendocinensis were investigated by studying allozyme and chromosome variation in natural populations and structural variation using herbarium specimens. Multivariate analyses of structural data demonstrated that C. gynodynama is clearly distinct from C. mendocinensis, and that sterile specimens similar to C. mendocinensis are intermediate between that species and C. gynodynama. The mean genetic distance between the two species, based on allozyme phenotypes at 17 enzyme‐coding loci, was 0.22 ± 0.12. The sterile putative hybrids had the expected heterozygous pattern at three enzyme‐coding loci at which the parental species were fixed for different alleles. Chromosome numbers are reported for the first time for both species and their putative hybrid. Carex mendocinensis had a different number in each of the three populations examined with n = 28, n = 29, or n = 30. Chromosome counts from one population of C. gynodynama revealed five plants with n = 25 and one with n = 26. Putative hybrids from this population exhibited irregular pairing at meiosis with 2n = ca. 55–57. Patterns of allozyme variation also suggest that C. mendocinensis has an outcrossing or mixed mating system but that C. gynodynama is an inbreeding species. Carex gynodynama exhibited very little variation in structure, habitat, or at the enzyme‐coding loci examined, suggesting that it may have experienced a genetic bottleneck relatively recently. Carex mendocinensis had higher levels of variation both within and between populations at enzyme‐coding loci and in structural features. This pattern of variation and a geographic distribution centered in serpentine areas of the Klamath–Siskiyou region, with disjunct smaller populations in serpentine areas farther south, suggest that C. mendocinensis once may have been a more widespread species.

Sex‐linked control of sex pheromone behavioral responses in European corn‐borer moths (Ostrinia nubilalis) confirmed with TPI marker gene

AbstractIn two races of European corn‐borer moths (ECB), the E‐race females emit and males respond to 99:1 sex pheromone blend of (E)/(Z)‐11‐tetradecenyl acetates, whereas the Z‐race females and males produce and respond to the opposite 3:97 pheromone blend of (E)/(Z)‐11‐tetradecenyl acetates, respectively. We previously have shown that female production of the final blend ratio is under control of a major autosomal locus but that the sequence of male upwind flight responses to the blend is controlled by a sex‐linked (Z‐linked) locus. This sex‐linked control of behavioral responses in crosses of E and Z ECB now is confirmed by use of sex‐linked TPI (triose phosphate isomerase) allozyme phenotypes to determine the origin of the sex chromosomes in F2 populations.F1 males from reciprocal E × Z crosses generate similar behavioral‐response profiles in wind‐tunnel studies, with moderate numbers responding to the Z pheromone and intermediate blends (35%–65% Z), but very few responding to the E pheromone. The F2 behavioral‐response profiles indicate that they are composed of 1:1 mixtures of hybrids and paternal profiles. Analysis of TPI allozyme differences allowed us to separate male F2 populations into individuals whose Z chromosomes both originated from their grandfathers, and individuals who had one Z chromosome originating from each grandparent. With these partitioned F2s, the TPI homozygotes exhibited behavioral‐response profiles very much like their grandfathers, whereas the TPI hybrids produced response profiles similar to their heterozygous F1 fathers. These results demonstrate incontrovertibly that the response to sex pheromone in male ECB is controlled by a sex‐linked gene that is tightly linked to the TPI locus and therefore is independent of the locus controlling pheromone blend production in females.

Biochemical analysis of allozyme copper and cadmium tolerance in fish using starch gel electrophoresis

AbstractThe in vitro effects of copper and cadmium on fish enzyme activity were assayed by combining the metals with the biochemical stains used to resolve these enzyme systems on starch gels. The effects of copper and cadmium on the activity of PGM‐2, GPI‐2 and IDH‐2 enzymes in mosquitofish were assayed using stain‐metal mixtures containing 2.0 ml 0.1 m CuSO4 · 5H2O or 0.1 m CdSO4. Enzymes whose activities were effected by copper in this initial test were resolved using a series of stain‐metal mixtures containing copper at lower concentrations to determine effect threshold concentration ranges and to determine concentration ranges that might produce differential effects on activity among allozymes of a single protein. Interspecific differences in the effect of copper on the activity of PGM‐2 enzyme variants were examined for 17 fish species from seven locations.Copper was found to effect the activity of PGM‐2, GPI‐2, and IDH‐2 enzymes in mosquitofish and intraspecific and interspecific differences existed in the copper sensitivity of enzymes in a number of the fish species tested. Allozyme phenotypes at the PGM‐2 locus in mosquitofish observed on test gels (0.9 mg Cu/L) suggests that two isoalleles, one copper‐tolerant and one copper‐sensitive, are present at this locus.

Apomictic parthenogenesis and genotypic diversity in Cypridopsis vidua (Ostracoda: Cyprididae)

Based on sex ratios, the crustacean subclass Ostracoda appears to have made frequent transitions from sexual to asexual reproduction. However few genetic data are available verifying their mode of reproduction. The current report provides such evidence for apomictic pathenogenesis in the cosmopolitan cypridid ostracode Cypridopsis vidua. Sex ratio analysis indicated that natural populations are exclusively female. Allozyme phenotypes in 18 of 20 natural populations showed strong departures from Hardy–Weinberg expectations at single loci, and three of four populations had non-random associations of phenotypes at MPI and PGM. Allozyme phenotypes at these loci suggested that polyploids were present in half these populations and were more common in the low arctic site than in the temperate sites. Most natural populations of C. vidua displayed high levels of genotypic diversity, with a total of 77 unique clones detected and up to 24 clones per pond. Breeding studies on 64 isofemale lines established that parthenogenesis is apomictic and that mutation rates are less than 10−3.

Survival and allozyme expression in diploid and triploid hybrids between chum, chinook, and coho salmon

Persistent problems in salmon aquaculture include the mortality of pen-cultured fish due to early maturation of males, the added expense of rearing juveniles of some species in freshwater, and the stress and mortality which can be associated with transferring those same species to sea water. Hybridizations may ameliorate some of these problems, and triploid hybrids frequently survive and growth much better than corresponding diploids. We determined the viabilities and allozyme phenotypes of progeny from diploid and triploid interspecific matings between coho ( Oncorhynchus kisutch), chum ( O. keta), and chinook ( O. tshawytscha) salmon. Allozyme data suggested that coho × chum salmon and chinook × coho salmon matings yielded progeny which were spontaneous gynogens, aneuploids, or possibly incompatible at regulatory loci. Combinations with promising survival included (female parent first) triploid chum × chinook salmon, diploid or triploid coho × chinook salmon, and possibly triploid chinook × coho salmon.

Naturally occurring variation in the restriction map of the amy region of Drosophila melanogaster.

The restriction maps of 85 alleles of the Amy region of Drosophila melanogaster from natural populations were surveyed. A subset of these were also scored for allozyme phenotype and adult enzyme activity of alpha-amylase. Large insertions were found in 12% of the alleles in a 15-kb region surrounding the two transcriptional units of the duplicated Amy locus. The low frequencies at which each of these large insertions were found are consistent with earlier reports of variation in other loci. Four small deletions were found in the region 5' to the Amy genes. Each was also rare in the population. Restriction site variation provided an estimate of per nucleotide heterozygosity of 0.006. Several statistically significant linkage disequilibria were observed between four polymorphic restriction sites and the allozymes. Adult alpha-amylase activity was correlated with the allozymes and with the polymorphism at one restriction site close to the transcriptional units.

Genetic Variability in the Florida Manatee (Trichechus manatus)

Tissue was obtained from 59 manatee ( Trichechus manatus ) carcasses salvaged from 20 counties in Florida. Allozyme phenotypes at 24 structural loci were determined by gel electrophoresis. Averages for the proportion of polymorphic loci and mean heterozygosity were 0.300 (range, 0.167–0.417) and 0.050 (range, 0.028–0.063), respectively. These estimates are equivalent to or higher than those generally reported for other species of marine mammals and do not support the hypothesis that body size and heterozygosity in mammals are related inversely. Among-region gene diversity accounted for only 4% of the total diversity. High rates of gene flow probably account for genetic homogeneity across regions. An F -statistic analysis revealed a general tendency toward excess homozygosity within regions. Management efforts to prevent future reductions in population size that would erode existing genic diversity should continue.

Confirmation of avian sex-chromosome linkage of liver cytosolic aconitase (ACO1).

Frequencies of liver cytosolic aconitase (ACO1) allozyme phenotypes in female zebra finches (Poephila guttata) conformed to a sex-chromosome-linked model of inheritance. Since birds are characterized by female heterogamety (ZZ males, ZW females), the observed absence of female heterozygotes for the cytosolic aconitase gene is interpreted as suggesting linkage of the ACO1 locus to the Z chromosome and hemizygous expression of this locus. Confirmation of this linkage assignment provides further support for the concept of evolutionary conservation of the avian Z chromosome.

NULL ALLELES AS A POSSIBLE CAUSE OF HETEROZYGOTE DEFICIENCIES IN THE OYSTER CRASSOSTREA VIRGINICA AND OTHER BIVALVES.

Populations of several marine bivalves exhibit significant deficiencies of heterozygotes (compared with the Hardy-Weinberg expectations) at some allozyme loci (Berger, 1983; Singh and Green, 1984; Zouros and Foltz, 1984). These deficiencies have usually been explained by invoking nonrandom mating, selection, or population structure (Wahlund effect). Less attention has been paid to the possibility that the deficiencies are due to the occurrence of null (nonreactive) alleles or to other factors causing allozyme loci to depart from a simple codominant model of genetic control. Null alleles may lead to heterozygote deficiencies if null heterozygotes are mistakenly scored as active homozygotes. Only a few studies have reported on inheritance of allozyme phenotypes in progeny from pair crosses

Genetic heterozygosity and production traits in natural and hatchery populations of bivalves

New data are presented and published data reviewed for several bivalve species regarding the correlations of electrophoretic phenotypes with performance characteristics such as growth and viability in natural and hatchery-reared populations. The relationship between allozyme phenotype and physiological traits depends strongly on the genetic structure of the population.

Allozyme variation in cultivars of Cucurbita pepo L.

Cultivars of Cucurbita pepo were analyzed for their isozyme phenotypes by horizontal starch gel electrophoresis. Considerable allozymic variation was observed between cultivars, especially in the aspartate aminotransferase and malate dehydrogenase isozyme systems. Each of the five fruit types represented in the 21 cultivars tested (zucchini, pumpkin, spaghetti, acorn, scallop and yellow straightneck) could be distinguished by specific allozymes or combination of allozymes. Cultivars within a fruit type gave very similar allozyme phenotypes and often could not be distinguished on the basis of the 6 assays used. Despite the outcrossing nature of the species, allozyme polymorphism within most cultivars was low and did not seriously interfere with the analysis. Approximately half of the hybrid lines tested gave heterozygous phenotypes at one or more loci, indicating that such loci could be used to screen for the percentage of hybrid seed obtained from crosses.

Cytogenetic localization by variation in electrophoretic allozyme phenotype: Drosophila Odh

A gene-dosage effect is characteristic of eukaryotic structural genes and is therefore useful in gene mapping. However, attributing quantitative variations in enzyme activity to a gene-dosage effect or other putative regulatory loci can be suspect when the locus in question may be inducible by variations in culture conditions. The problem of controlling for allele-specific variations in activity and regulation can be circumvented in Drosophila melanogaster by the use of synthetic duplications and deficiencies in conjunction with enzyme polymorphism. A method for constructing segmental aneupliods heterozygous for electrophoretic variants of octanol dehydrogenase (Odh) is presented which permitted variations in allozyme phenotype and enzyme activity--which show a strict dosage dependency--to be produced simultaneously. The structural gene region for Odh was identified using T(Y;A) stocks and the deficiency M(3)S31 was used to assign the locus to polytene band region 86D1-4. With this method a segmental aneuploid survey of Drosophila for purposes of gene localization can be accomplished in one generation with appropriate stocks.

Genic Variability, Dispersal, and Differentiation in Two Species of Ophiuroids from Southern California

Genic Variability, Dispersal, and Differentiation in Two Species of Ophiuroids from Southern California

GENOTYPIC DIVERSITY IN OENOTHERA LACINIATA (ONAGRACEAE), A PERMANENT TRANSLOCATION HETEROZYGOTE.

Electrophoretic studies have revealed remarkable variability within and among populations of several unisexual animal species. Multiple genotypes, detected by various allozyme phenotypes, exist for unisexual insects (Parker et al., 1977; Suomalinen et al., 1977; Mitter et al., 1979), fishes (Schultz, 1977), lizards (Uzzell and Darevsky, 1975; Parker and Selander, 1976) and annelids (Christensen et al., 1976; Jaenike and Selander, 1979). The few studies employing allozymes as genetic markers for clonal plant species have either focused closely on one or a few populations (Solbrig and Simpson, 1974; Hancock and Wilson, 1976; Hancock, 1977; Steiner and Levin, 1977; Silander, 1979) or concentrated mainly on interpopulational differences (Solbrig, 1971; Levin, 1975; Levy and Winternheimer, 1977; Ellstrand and Levin, 1980a, 1980b). No study has yet described genotypic diversity both within plant populations and over the range of a clonal plant species. The object of this study is to obtain a minimal determination of levels of diversity in a clonal plant species and compare these levels with those exhibited within and among populations of unisexual animal species. The species chosen for study is Oenothera laciniata Hill, an annualwhich occurs in disturbed sandy soils from Texas east to the Atlantic coast and north to Illinois and New Jersey (P. Raven, pers. comm.). This species is a permanent translocation heterozygote, cytogenetically studied throughout its range (Hecht, 1950; Gregory and Klein, 1960; McMullen, 1966; Cleland, 1968; P. Raven and W. Dietrich, pers. comm.). Permanent translocation heterozygosity is an unusual genetic system which results in an effectively asexual mode of reproduction (for details, see Cleland, 1972). Oenothera laciniata is probably a derivative of 0. grandis Smyth, an outcrosser with a conventional genetic system, which occurs primarily in south and central Texas (Munz, 1965; Ellstrand and Levin, 1980b).

Intergall Migration in the Aphid Genus Pemphigus12

Aphids of the gall-forming species Pemphigus populitransversus (Hemiptera: Aphidae) exhibit surprising amounts of within-gall diversity for allozyme phenotypes. The patterns are inconsistent with meiotically produced variation. Lack of variation within galls wrapped in cloth bags indicates that the variation is the result of among-gall dispersal by immature aphids.