Multiple-Locus Heterozygosity and the Physiological Energetics of Growth in the Coot Clam, MULINIA LATERALIS, from a Natural Population

The relationship between individual energy budgets and multiple-locus heterozygosity at six polymorphic enzyme loci was examined in Mulinia lateralis. Energy budgets were determined by measuring growth rates, rates of oxygen consumption, ammonia excretion and clearance rates. Enzyme genotypes were determined using starch gel electrophoresis. Growth rate and net growth efficiency (the ratio of energy available for growth to total energy absorbed) increased with individual heterozygosity. The positive relationship between observed growth and multiple-locus heterozygosity was associated with a negative relationship between routine metabolic costs and increasing heterozygosity. Reduction in routine metabolic costs explained 60% of the observed increased growth of more heterozygous individuals. When routine metabolic costs were standardized for differences in feeding rates, these standard metabolic costs explained 97% of the differences in growth rate. Lower standard metabolic costs, associated with increasing heterozygosity, have been proposed as a physiological mechanism for the relationship between multiple-locus heterozygosity and growth rate that has been reported for a variety of organisms, ranging in diversity from aspens to humans. This study demonstrates that reduction of standard metabolic costs, at least in clams, accounts for virtually all of the differences in growth rate among individuals of differing heterozygosity.     

Effects of copper on the fitness of the Chilean scallop Argopecten purpuratus (Mollusca: Bivalvia)

Exposure to high concentrations of metals can affect populations and individuals at morphological, physiological, biochemical or genetic levels. Metal pollution is a source of environmental stress that can have deleterious effects on organisms and generate selective pressure upon populations. This work attempts to establish whether concentrations of copper, above physiological requirements, can affect the genetic structure of a cohort of Chilean scallop Argopecten purpuratus. Following the determination of LC₅₀ for 96 h experiments, other acute toxicity tests were carried out, exposing the juveniles to solutions of 150 ppb copper for 120 h. Dead, surviving and control individuals from these bioassays were genetically characterized for five polymorphic loci, Isocitrate dehydrogenase (Idh), Octopine dehydrogenase (Ocdh), Phosphogluconate dehydrogenase (Pgd), Leucine aminopeptidase (Lap) and Phosphoglucose isomerase (Pgi). Results showed no significant differences in allele and genotypic frequencies between surviving and dead individuals, although for the same groups significant differences were found in estimated mean heterozygosity. Pgi and Ocdh showed significantly different heterozygosity values for dead and surviving individuals. A positive relationship between multilocus heterozygosity and survival was found for young A. purpuratus exposed to high copper concentrations; thus, we found evidence of a differential response to exposure to high copper concentrations, related to degree of heterozygosity.     

Allozyme variation in the solanaceous fruit fly Bactrocera latifrons (insecta: diptera: tephritidae) from peninsular malaysia

• 1.1. Bactrocera latifrons fruit flies recovered from four solanaceous fruits (Capsicum annuum, Lycopersicon esculentum, Solanum pseudocapsicum and Solanum melongena) in Peninsular Malaysia were analyzed for a total of 15 gene-enzyme systems comprising 21 loci.
• 2.2. Eleven loci—aAdh, Aldox, Ald, Est-F, Est-S, Hk-F, Ldh, cMdh, Me, Pep-A and Pep-C—were invariant.
• 3.3. Of the polymorphic loci, cathodal alcohol dehydrogenase, glucose phosphate isomerase, glycerol-3-phosphate dehydrogenase, hydroxybutyrate dehydrogenase, isocitrate dehydrogenase, anodal malate dehydrogenase and phosphoglucomutase were represented by two alleles each, while hexokinase-S, peptidase-B and phosphogluconate dehydrogenase were represented by three alleles each.
• 4.4. The proportion of polymorphic loci ranged from 0.28 to 0.33, while the mean heterozygosity ranged from 0.04 to 0.13.
• 5.5. The genetic variability is associated with the host range.

     

Electrophoretic and Karyological Characters of the Gyrinocheilid Fish,Gyrinocheilus aymonieri

A diploid karyotype of 2n48 was confirmed for Gyrinocheilus aymonieri and is interpreted as a primitive condition within the Cypriniformes. Levels of allozyme variation measured from commercially obtained samples were comparable to those of most diploid cypriniform fishes; products of rive of 23 loci were polymorphic and heterozygosity was measured at −0.05. Gyrinocheilus aymonieri exhibits derived conditions for a number of isozyme characters: two non-interactive acid phosphatase loci were found to be expressed in brain, and the formation of interlocus heteropolymers was non-random for several multimeric enzymes including glucose-6-phosphate isomerase, l-lactate dehydrogenase and malate dehydrogenase. Additional information on gene expression in the cobitids and Old World cyprinids may clarify the autapomorphic or synapomorphic nature of these derived conditions in G. aymonieri.     

Genetic diversity of wild and cultured swamp eel (Monopterus albus) populations from central China revealed by ISSR markers

Asian swamp eel is a highly commercial fish, primarily for China and other Asian countries. The aim of this paper is to evaluate the genetic diversity of wild and cultured samples of Asian swamp eel Monopterus albus using ISSR markers. A total of 129 individuals belonging to three wild samples, Xiantao (XT), Huanggang (HG), Xinyang (XY) and three cultured samples, Wuhan (WH), Jingzhou (JZ) and Nanjing (NJ) were randomly selected for genetic analysis. Twelve ISSR primers were used for screening the six populations and 110 loci were obtained. The polymorphic loci were estimated to be 54%, 56.3%, 58.2%, 60.6%, 69.5% and 71% in NJ,WH, JZ, XT, HG and XY samples, respectively. Average heterozygosity value varied from 0.1956 to 0.2449. The three wild samples showed higher genetic diversity than the cultured samples (P < 0.05), including polymorphic bands (PPB), observed number of alleles per locus (_to), effective number of alleles per locus (Ne), Nei’s gene diversity index (H) and Shannon’s information index (I).     

Development of 240 novel EST-SSRs in Eucalyptus L’Hérit

Simple sequence repeat (SSR) markers derived from expressed sequence tag (EST) resources provide great potential for comparative mapping, direct gene tagging of quantitative trait loci and functional diversity studies. Here we report on the development of 240 novel EST-SSRs for the important tree genus Eucalyptus L’Hérit. Of the 240 EST-SSR loci, 218 (90.8 %) were polymorphic among 12 individuals of E. grandis Hill ex Maiden, with the number of alleles per locus (N _a), observed heterozygosity (H _o), expected heterozygosity (H _e) and polymorphic information content (PIC) averaging at 5.0, 0.403, 0.598 and 0.529, respectively. High rates of cross-species/subgenus amplification were observed. The EST-SSRs developed herein would be a valuable addition of functional markers for genetics and breeding applications in a wide range of eucalypt species. The primer sequences for the 240 EST-SSRs have been deposited in the Probe database of GenBank (IDs Pr016588534–773).     

Enzyme polymorphism in Mansonia uniformis, a mosquito vector of brugian filariasis

Three temporal samples of a wild population of Mansonia uniformis were analysed for genetic variation at six gene-enzyme systems. Adenylate kinase, hexokinase (3 loci) and cathodal malate dehydrogenase were monomorphic. Phosphoglucomutase, glucose phosphate isomerase, isocitrate dehydrogenase and anodal malate dehydrogenase were polymorphic. Each of the polymorphic loci was represented by three alleles. The average heterozygosity or gene diversity was 0.0437.     

EFFECTS OF POPULATION BOTTLENECKS ON GENETIC DIVERSITY AS MEASURED BY ALLOZYME ELECTROPHORESIS

Low levels of allozyme heterozygosity in populations are often attributed to previous population bottlenecks; however, few experiments have examined the relationship between heterozygosity and bottlenecks under natural conditions. The composition and number of founders of 55 experimental populations of the eastern mosquitofish (Gambusia holbrooki), maintained under simulated field conditions, were manipulated to examine the effects of bottlenecks on three components of allozyme diversity. Correlations between observed and expected values of allozyme heterozygosity, proportions of polymorphic loci, and numbers of alleles per locus were 0.423, 0.602, and 0.772, respectively. The numbers of polymorphic loci and of alleles per locus were more sensitive indicators of differences in genetic diversity between the pre-bottleneck and post-bottleneck populations than was multiple-locus heterozygosity. In many populations, single- and multiple-locus heterozygosity actually increased as a result of the founder event. The weak relationship between a population's heterozygosity and the number and composition of its founders resulted from an increase in the variance of heterozygosity due to drift of allele frequencies. There was little evidence that selection influenced the loss of allozyme variation. When it is not possible to estimate heterozygosity at a large number of polymorphic loci, allozyme surveys attempting to detect founder events and other types of bottlenecks should focus on levels of locus polymorphism and allelic diversity rather than on heterozygosity.     

Heterosis at Allozyme Loci under Inbreeding and Crossbreeding in PINUS ATTENUATA

The dependence of heterosis at isozyme loci on inbreeding and crossbreeding was studied in 10-yr-old trees of knobcone pine (Pinus attenuata Lemm.). Heterozygosity was determined at 24 polymorphic isozyme loci and related to the rate of vegetative growth and cone production. The inbreds, created by selfpollination, had 46% of the heterozygosity of their mothers; the crossbreds, created by interpopulation crossing, had 155% of the heterozygosity of their mothers. Within the crossbreds, heterozygosity was positively correlated with trunk growth, but negatively correlated with cone production. Results in the crossbreds, however, were strongly influenced by a few individuals that showed unusually slow growth, high reproduction and low heterozygosity. Without those individuals, there was no relationship of heterozygosity to either growth or reproduction.—Within the inbreds, heterozygosity was positively correlated with both trunk growth and cone production. Each locus that was heterozygous in the mothers was calculated to mark about 3% of the genome for identity by descent in the inbred progeny; the total proportion of the genome marked was between 10 and 11%. Using these estimates to relate heterozygosity to the inbreeding coefficient (F) gave estimates of inbreeding depression per unit of F that fell within the range of published values for conifers. The strength of heterosis found among the inbreds suggests that single-locus or multilocus overdominance should be exceedingly difficult to detect in natural populations of predominantly outcrossing species.     

Biochemical genetics of hybrid sunfish: Differential survival of heterozygotes

Allelic segregation in reciprocal backcrosses involving the largemouth bass (Micropterus salmoides) and the F₁ hybrid (largemouth bass × smallmouth bass, M. dolomieui) was investigated to determine the extent of euheterosis and luxuriance. The frequencies of allelic isozymes encoded in the lactate dehydrogenase E, malate dehydrogenase B, and isocitrate dehydrogenase loci were determined for reciprocal backcross progeny subjected to different selection pressures. The progeny of the backcross (male F₁ × female largemouth bass) underwent a rapid loss of heterozygous individuals in a natural pond environment. When the offspring of this same mating were placed in artificial pools, where cannibalism is the main source of mortality, heterozygosity was advantageous. There was a marked correlation of increased heterozygosity at these enzyme loci with an increased growth rate. None of the above responses to selection was observed when the F₁ hybrid served as the maternal parent in the reciprocal backcross. A maternal factor in the egg cytoplasm may influence the expression of heterosis.     

Population genetics studies of half-smooth tongue sole Cynoglossus semilaevis using ISSR markers

Inter-simple sequence repeat (ISSR) analysis was performed in order to evaluate the genetic diversity of wild and hatchery samples of half-smooth tongue sole Cynoglossus semilaevis. A group of 200 genotypes belonging to four wild samples, Laizhou (LZ), Weihai (WH), Qingdao (QD), Rizhao (RZ) and one hatchery sample, Mingbo (MB) were screened using 15 different ISSR primers. A total of 137 loci were produced in the five studied samples. 41.80%, 45.26%, 44.27%, 42.86% and 41.59% of these loci were polymorphic over all the genotypes tested in LZ, WH, QD, RZ and MB samples, respectively. The number of polymorphic loci detected by single primer combination ranged from 2 to 7. The average heterozygosity of LZ, WH, QD, RZ and MB samples were 0.0710, 0.0814, 0.0793, 0.0727 and 0.0696, respectively. The WH sample showed a higher genetic diversity including total number of ISSR bands (P < 0.05), total number of polymorphic bands (P < 0.05), average heterozygosity (P < 0.05) and total number of genotypes (P < 0.05) than all the other samples. Among the five studied samples, the hatchery sample (MB) showed the lowest genetic viability.     

A mannose phosphate isomerase polymorphism in the Isopod Asellus aquaticus

A mannose phosphate isomerase locus in Asellus aquaticus is highly polymorphic in two populations examined in Britain. Breeding studies indicate four classes of electrophoretic alleles based on mobility differences, a further null allele, and probable genetically determined variation in enzyme activity between individuals with the same electrophoretic alleles. No linkage with the polymorphic glucose phosphate isomerase and phosphoglucomutase loci was detectable.     

Isolation and characterization of microsatellite markers for the heavily exploited rockfish Sebastes schlegeli, and cross-species amplification in four related Sebastes spp.

Here we report development and characterization of 14 polymorphic microsatellite loci from Sebastes schlegel. Polymorphism at these loci revealed from 3 to 23 alleles. The observed heterozygosity ranged from 0.34 to 1.00, and the expected heterozygosity ranged from 0.31 to 0.95. No linkage disequibrium was found. Two loci were significantly deviated from HWE (P < 0.01). The 14 loci were also surveyed in four other Sebastes species and 12 loci successfully amplified, where allelic diversity ranged from highly polymorphic to monomorphic. These results demonstrate these microsatellite markers can be used for the study of intra- and inter-specific genetic diversity.     

Observations on genetic diversity of Bulinus cernicus (Gastropoda: Planorbidae) from Mauritius

Enzyme variation has been investigated in eight populations of Bulinus cernicus from Mauritius using isoelectric focusing and starch gel electrophoresis. Of 11 loci examined for 10 enzyme systems, seven were found to be polymorphic. These were malate dehydrogenase, glucose phosphate isomerase, acid phosphatase (A and B), 3-hydroxybutyrate dehydrogenase, 6-phosphogluconate dehydrogenase and NADH-dependent diaphorase. Invariant loci were phosphoglucomutase, xanthine oxidase, fructokinase and αaL-glycerophosphate dehydrogenase. The percentage of polymorphic loci within the populations ranged from 9.1% to 54.5%. The average heterozygosity per population for all loci ranged from 0,009 to 0.203. Genetic distance values ranged from 0.01 to 0.3 with the higher values associated with comparisons of populations from the north-west and south-east of the island. A comparison of data sets for 1980 and 1986 revealed the allelic frequencies at five enzyme loci to be remarkably consistent.     

Analysis of genetic variation in selected stocks of hatchery flounder,Paralichthys olivaceus,using AFLP markers

Amplified fragment length polymorphism (AFLP) analysis was performed in order to evaluate genetic characteristics of one common population and two selective hatchery populations of flounder Paralichthys olivaceus. A group of 60 genotypes belonging to three populations was screened using 10 different AFLP primer combinations. A total of 491 loci were produced in the three studied populations. The loci of 65.78%, 61.47% and 60.92% were polymorphic over all the genotypes tested in common, susceptible and resistant populations, respectively. The number of polymorphic loci detected by single primer combination ranged from 21 to 43. The average heterozygosity of common, susceptible and resistant populations was 0.1656, 0.1609 and 0.1586, respectively, which showed no significant difference. Compared with the common population, the two selective hatchery populations, susceptible and resistant, showed significant genetic differences including a smaller (P < 0.05) number of total loci, a smaller (P < 0.05) number of total polymorphic loci and a smaller (P < 0.05) percentage of low frequency (0–0.2) polymorphic loci. AFLP banding pattern was transformed into binary data and matrices were processed with POPGENE and TFPGA software. Similarity relationships were described graphically by a dendrogram, which clustered the three populations. The AFLP fingerprinting technique was confirmed to be a reproducible and sensitive tool for the study of population genetics of flounder. The present study confirmed that it was important to detect the genetic variability of the selective hatchery populations for the conservation of natural flounder resources.     

Application of Microsatellite Primers Developed for Polistes in the Independent-Founding Wasp Polists satan Bequaert (Hymenoptera: Vespidae)

Microsatellite primers developed for a given species are sometimes useful for another in the same genus and in other genera within the same family, making possible to search for pre-existing suitable primers in the databanks such as GenBank. We examined whether existing primers developed for Polistes could be used for Polistes satan Bequaert. We tested 50 microsatellite primers from three Polistes species and found that six microsatellite loci show polymorphism in size in P. satan. These six loci were highly polymorphic, having four to 15 alleles in P. satan with an expected heterozygosity of 0.525?C0.832. These loci can be used to study parameters concerning genetic relatedness such as social interactions in colonies and genetic conflicts of interest among nestmate individuals.     

Protein polymorphism in native goats from central Argentina

Under the name of Creole goats, individuals of various origins, morphological and productivity characters are grouped. To characterize the genetic pool of goats from different sources in central Argentina, protein polymorphism revealed by electrophoresis was analyzed. A total of 109 adult animals from Santa Marı́a, Colón and Ischilı́n Districts, Córdoba Province, were studied. The red cells lysates were subjected to starch gel electrophoresis and specific staining procedures to reveal the activity of different enzymes and hemoglobin. Separation of plasmatic proteins was carried out by electrophoresis in polyacrylamide gel and stained with Coomassie Blue. From a total of 14 loci analyzed, eight were polymorphic in at least one flock. Four codominant alleles were detected in the locus βHemoglobin (βHb); three alleles in malic enzyme (Me), glucose 6 phosphate dehydrogenase (G6pdh) and lactate dehydrogenase (Ldh) and two alleles in catalase (Cat), transferrin (Tf), esterase-2 (Es-2) and phosphoglucomutase (Pgm). In all the cases, the observed genotype frequencies were not significantly different from those expected from Hardy–Weinberg equilibrium. The proportion of polymorphic loci (P%) varied between 21.4% and 42.9% and mean heterozygosity (H), between 0.061 and 0.117. Alleles at loci Cat, Me and Es-2 showed significantly different frequencies according to the sample origin. The flock from Colón District presented the highest levels of polymorphism. This is the only stock which includes hybrids of varying grade between Creole stocks and male specimens from Saanen and Nubian breeds.     

Tetranucleotide microsatellites for the barnacle Megabalanus coccopoma (Darwin, 1854)

The barnacle Megabalanus coccopoma is indigenous to the tropical Pacific Ocean, but was recently introduced to the coastal waters of the southeastern U.S.A. As part of a larger effort to investigate the population dynamics of this introduction, we designed 13 microsatellite primers specific to M. coccopoma and developed the accompanying polymerase chain reaction (PCR) conditions. We tested these primers on 42 individuals of M. coccopoma collected from two sampling locations in coastal Georgia, USA. The 13 loci developed showed means of 24.5 alleles per locus, 0.93 expected heterozygosity, 0.67 observed heterozygosity, and 0.91 polymorphic information content. The high variation observed within these microsatellite loci makes them useful tools for testing hypotheses related to population genetics, including source-sink dynamics for range expansions and rates of self-fertilization and outcrossing.     

Isolation and characterization of microsatellite loci from <Emphasis Type="Italic">Spodoptera exigua</Emphasis> (Lepidoptera: Noctuidae)

Ten polymorphic microsatellite loci were isolated and characterized from Spodoptera exigua (Hübner), which is a worldwide economic pest on various crops. The isolated loci were polymorphic, with 3–15 alleles in 40 individuals from four regional populations in Korea. The analyses revealed that 40 individuals had different multilocus genotypes, with the expected heterozygosity ranging from 0.133 to 0.899. Eight of the ten loci did not deviate significantly from Hardy-Weinberg equilibrium. The isolated markers will facilitate population genetic studies of S. exigua.     

Isolation and characterization of polymorphic microsatellite markers for the endangered tree <Emphasis Type="Italic">Handeliodendron bodinieri</Emphasis> (Sapindaceae)

Nine polymorphic microsatellite loci were developed and characterized for Handeliodendron bodinieri, an endangered tree endemic to karst forest in southwest China. Each locus displayed between 4 and 11 alleles. The observed heterozygosity ranged from 0.345 to 0.931 and expected heterozygosity varied from 0.414 to 0.824. The combined probabilities of paternity exclusion over all loci were 0.931 for P _r(Ex₁) and 0.993 for P _r(Ex₂), respectively. These loci represent a powerful tool in investigating gene flow and population structure in natural populations of H. bodinieri.