Genetic variability in white-tailed deer (Odocoileus virginianus) and its relationship to environmental parameters and herd origin (Cervidae)

Allozyme variation was examined in 1571 white-tailed deer (Odocoileus virginianus) from 29 localities in Tennessee by starch gel electrophoresis. For 11 polymorphic loci, sex-related, age-related and temporal differences were minimal. However, significant spatial hererogeneity was evident in genotypes (contingency table results), allele frequencies (F _ST=0.057) and heterozygosity. Heterozygosity ranged from 16.9% to 26.8% with a mean of 22.9%. The spatial pattern of allele frequencies determined from Rogers' coefficients of genetic similarity indicated associations based on geographic proximity and stocking history. In hierarchial analyses, physiographic regions accounted for more of the total gene diversity than herd origin groups (populations of similar origin) but less than individual populations. For five loci, physiographic regions accounted for more of the gene diversity than populations, suggesting a selection role in the observed genetic variability. Bivariate and canonical correlation analyses revealed significant associations between environmental and genetic variables. Temperature variables and allele frequencies for three loci (alcohol dehydrogenase, alpha-glycerophosphate dehydrogenase, sorbitol dehydrogenase) had the prominent roles in the multivariate association between environmental and genetic variables. Herd origin, gene flow and selection appear to be involved in the gene diversity in deer from Tennesee.     

Adaptive significance of amylase polymorphism in Drosophila I. The geographical pattern of allozyme polymorphism at the amylase locus in Drosophila subobscura

Allelic variation at the Amy locus was studied in eight natural populations from the central and northern range of D. subobscura, and the geographical pattern of Amy polymorphism over the range of this species was described. Even though regional and local differences in gene frequencies were found, in general the same alleles occur at high, intermediate and low frequencies, in nearly all populations. There are no significant differences in allele frequencies, but there is significant difference in the degree of heterozygosity among groups of populations from the northern, central and southern range. An analysis of population subdivision indicates that heterogeneity within populations is higher than between populations. Genetic distance values indicate that there is a variable degree of geographical differentiation between local populations. Variability within and between continental and insular populations is also discussed.     

GENETIC VARIATION IN THE HOMOSPOROUS FERN PELLAEA ANDROMEDIFOLIA

Genetic variability was examined in nine sexual and three apogamous natural populations of the homosporous fern Pellaea andromedifolia by electrophoretic analysis of enzymes specified by eight loci. Genetic interpretations of heterozygous banding patterns were determined by segregational analysis of gametophytes. High levels of segregating heterozygosity characterized the sexually reproducing populations, and genotype frequencies at the five polymorphic loci were consistent with those expected under conditions of random intergametophytic mating. Multiple-banded patterns in the apogamously reproducing populations resembled those of heterozygous sexual individuals, but did not segregate. The results suggest that genetic variation in sexual homosporous vascular plants is produced by cross fertilization of genetically different gametes and may not result from pairing between homoeologous chromosomes carrying duplicated loci as previously thought.     

HETEROZYGOSITY AND DEVELOPMENTAL STABILITY UNDER INBREEDING AND CROSSBREEDING IN PINUS ATTENUATA

The relationship between stability of annual trunk growth and heterozygosity at 24 polymorphic isozyme loci was studied in 10-year-old trees of knobcone pine (Pinus attenuata Lemm.) that were the products of contrasting systems of mating, self-, and interpopulation cross-pollination. Heterozygosity and variability of trunk growth were strongly related only when inbreds and crossbreds were compared; the crossbreds showed greater residual variability on an absolute scale, and greater responsiveness to climate on both absolute and relative scales. Within the inbreds there was no evidence of a relationship between heterozygosity and variability. Within the crossbreds, only one trait, a measure of relative trunk growth rate, showed a relationship with heterozygosity, and indicated greater variability of the more heterozygous trees. These results, and others in the literature, suggest that the relationship of heterozygosity to homeostasis for fitness components is neither simple nor monotonic; it varies between scales of measurement, genetic backgrounds, and environments.     

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.     

Genetic variability in Plantago species in relation to their ecology

Summary A survey of enzyme variability in several populations of Plantago major in the Netherlands has been made. Nine of 36 loci were found to be polymorphic. The most extensively studies population showed 7 polymorphic loci (19%). The average heterozygosity was 0.005, a low value since P. major is predominantly inbreeding; a first estimate of the outcrossing rate is only 10%. All nine variable loci show simple Mendelian inheritance, seven of them could be placed into four different linkage groups. Marked differences in allele frequencies were found between two subspecies: ssp. major and ssp. pleiosperma. Two enzyme loci possess subspecies-specific alleles, Pgm-1 and Got-1. The most likely explanation of this phenomenon is the existence of fitness differences, caused either by the enzyme loci themselves or by linked loci.Grassland Species Research Group Publication no. 14     

The involvement of alcohol dehydrogenase and aldehyde dehydrogenase in alcohol/aldehyde metabolism in Drosophila melanogaster

In this study we have examined the roles of alcohol dehydrogenase, aldehyde oxidase, and aldehyde dehydrogenase in the adaptation of Drosophila melanogaster to alcohol environments. Fifteen strains were characterized for genetic variation at the above loci by protein electrophoresis. Levels of in vitro enzyme activity were also determined. The strains examined showed considerable variation in enzyme activity for all three gene-enzyme systems. Each enzyme was also characterized for coenzyme requirements, effect of inhibitors, subcellular location, and tissue specific expression. A subset of the strains was chosen to assess the physiological role of each gene-enzyme system in alcohol and aldehyde metabolism. These strains were characterized for both the ability to utilize alcohols and aldehydes as carbon sources as well as the capacity to detoxify such substrates. The results of the above analyses demonstrate the importance of both alcohol dehydrogenase and aldehyde dehydrogenase in the in vivo metabolism of alcohols and aldehydes.     

EXPERIMENTAL STUDIES IN PONDEROSA PINE. I. RELATIONSHIP BETWEEN VARIATION IN PROTEINS AND MORPHOLOGY

Ponderosa pine from California (Pinus ponderosa var. ponderosa) were crossed to one another and also to individuals from the Rocky Mountains (P. p. var. scopulorum). All crosses involved a single mother and a single pollen donor. Patterns of inheritance of electrophoretically-detectable loci followed Mendelian expectations with one exception. Shikimate dehydrogenase showed unpredictable banding patterns in intervarietal crosses. Variability at these biochemical loci was compared to variability at 14 morphometric characters. The relationship between these two levels of variation is complex and permits only one generalization: variability at one level is not a good predictor of variability at the other level.     

Genetic divergence between populations of two closely related troglobitic beetle species (Speonomus: Bathysciinae,Coleoptera)

Genetic variability and divergence at 13 enzyme loci were studied in two species of troglobitic beetles (Speonomus zophosinus andhydrophilus 12 populations) collected from the Pyrenees mountains. These allopatric species exhibit a high degree of specialization to underground life and a very small geographical range. Four diagnostic loci arePgi, Est-2, Pac-1, Phi. Within each species polymorphic loci exhibited marked spatial variation of allele frequencies, sometimes over short distances (5–10 km). The levels of genetic variability are comparable to those observed in non-cave invertebrates (frequency of polymorphic loci: 0.31; average expected heterozygosity: 0.112±0.015). Moreover, a single species showed variability in the average level of heterozygosity (0.06 to 0.172). Patterns of genetic differentiation among species were also studied; mean genetic distance (D: 0.263±0.010) between the twoSpeonomus species was of the same order of magnitude as most data reported in the literature between species. A significant heterozygote deficiency occurs in local populations and for all loci. This deficit does not vary from locus to locus. Several hypotheses were examined in an attempt to account for these observations in connection with the species biology. This deficit probably is due to the breeding structure of the population (inbreeding and assortative mating) coupled with limited dispersal ability.     

Selection on structural allelic variation biases plasticity estimates

Wang and Althoff (2019) explored the capacity of Drosophila melanogaster to exhibit adaptive plasticity in a novel environment. In a full‐sib, half‐sib design, they scored the activity of the enzyme alcohol dehydrogenase (ADH) and plastic responses, measured as changes in ADH activity across ethanol concentrations in the range of 0–10% (natural variation) and 16% (the novel environment). ADH activity increased with alcohol concentration, and there was a positive association between larval viability and ADH activity in the novel environment. They also reported that families exhibiting greater plasticity had higher larval survival in the novel environment, concluding that ADH plasticity is adaptive. However, the four authors now concur that, since the study estimated plasticity from phenotypic differences across environments using full‐sib families, it is not possible to disentangle the contributions of allele frequency changes at the Adh locus from regulatory control at loci known to influence ADH activity. Selective changes in allele frequencies may thus conflate estimates of plasticity; any type of “plasticity” (adaptive, neutral, or maladaptive) could be inferred depending on allele frequencies. The problem of scoring sib‐groups after selection should be considered in any plasticity study that cannot use replicated genotypes. Researchers should monitor changes in allele frequencies as one mechanism to deal with this issue.     

Genetic variability in Hoplias malabaricus (Osteichthyes: Erythrinidae) in fluvial and lacustrine environments in the Upper Paraná river floodplain (Paraná State,Brazil)

Genetic variability in Hoplias malabaricus, from two localities in the upper Paraná River floodplain, was investigated by starch and polyacrylamide gel electrophoresis. A total of 52 specimens were analyzed for 14 enzymatic systems. Twenty-three gene loci of 13 enzymatic systems (AAT, ACP, ADH, GDH, G6PDH, GPI, IDH, LDH, MDH, MEP, PGM, PER, and SOD) were analyzed by starch gel electrophoresis (Penetrose-30). The EST system was analyzed by polyacrylamide gel electrophoresis, and one polymorphic locus was found (EST-1). Twenty-four loci were detected. The proportion of polymorphic loci was 37.5% in the lagoon and 33.3% in the river. Significant differences in allele frequencies of five loci were found between specimens from the two environments. Expected mean heterozygosity (H _e = 0.14) is the same in the river and lagoon, however, Nei's genetic distance (D) between the population of the two locations was 0.049.     

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.     

Electrophoretic variability in natural populations of Drosophila melanogaster and Drosophila simulans

Genetic variation at 59 gene loci coding for enzymes (50) and larval proteins (9) has been studied in sympatric populations of Drosophila melanogaster and D. simulans from insular and continental origin. The average number of alleles per locus, the mean proportion of polymorphic loci and the mean heterozygosity are similar both within and between species. There are however some significant differences between D. simulans populations in the genotypic frequencies for four polymorphic loci.     

Isozyme variability in species of the genus Drosophila. VII. Genotype-environment relationships in populations of D. melanogaster from the eastern United States

Collections of D. melanogaster were analyzed for genetic variation at nine enzyme loci. Allelic frequencies were determined, and comparisons between observed phenotypic proportions and those expected under equilibrium conditions were made. A significant tendency toward homozygote excess was noted. Relationships between patterns of genetic variability and between patterns of genetic and environmental variability were examined by the method of principal components and correlation analysis. Several of the loci showed a clinal pattern in gene frequencies, and overall there was an appreciable amount of genetic-genetic and genetic-environmental association.This work was supported by PHS Research Grant No. GM 11546 and AEC Contract No. AT-(40-1)-3980. Paper No. 4026 of the Journal Series of the North Carolina Agricultural Experiment Station, Raleigh, North Carolina.     

Analysis of the relationship between allozyme heterozygosity and fitness in the rare Gentiana pneumonanthe L.

Especially for rare species occurring in small populations, which are prone to loss of genetic variation and inbreeding, detailed knowledge of the relationship between heterozygosity and fitness is generally lacking. After reporting on allozyme variation and fitness in relation to population size in the rare plant Gentiana pneumonanthe, we present a more detailed analysis of the association between heterozygosity and individual fitness. The aim of this study was to test whether increased fitness of more heterozygous individuals is explained best by the ‘inbreeding’ hypothesis or by the ‘overdominance’ hypothesis. Individual fitness was measured during 8 months of growth in the greenhouse as the performance for six life-history parameters. PCA reduced these parameters to four main Fitness Components. Individual heterozygosity was scored for seven polymorphic allozyme loci. For some of these loci (e.g. Aat3, Pgm1 and 6Pgdh2) heterozygotes showed a significantly higher relative fitness than homozygotes. To test the inbreeding model, regression analyses were performed between each Fitness Component and the number of heterozygous loci per individual. Multiple regressions with the adaptive distance of five loci as independent variables were used to test the overdominance model. Only the inbreeding model was a statistically significant explanation for the relationship between heterozygosity and fitness in G. pneumonanthe. The number of heterozygous loci was significantly negatively correlated with the coefficients of variation of three of the six initially measured fitness parameters. This suggests a lower developmental stability among more homozygous plants and may explain the higher phenotypic variation in small populations of the species observed earlier. The importance of the results for conservation biology is discussed.     

Characterization of 14 tetranucleotide microsatellite loci derived from Pacific herring

Spawning aggregations of Pacific herring (Clupea pallasi) often exhibit significant interannual variation in allele frequencies of neutral gene markers. We isolated 14 tetranucleotide microsatellites to examine hypothetical processes that may produce this unique genetic signal. We developed and tested primer pairs for each locus and then estimated locus variability in samples (n = 60) from two populations. The number of alleles per locus ranged from five to 49. The expected heterozygosity across loci and populations ranged from 0.20 to 0.96. These microsatellites will be useful for estimating genetic variation in herring on a fine geographical scale.     

Effect of multiple-locus heterozybosity and salinity on clearance rate in a brackish-water clam,Rangia cuneata (Sowerby)

Previous studies of several species of marine bivalves and gastropods have reported a positive correlation between growth or size and level of multiple-locus heterozygosity. There is some evidence that the growth advantage of relatively heterozygous individuals is due to a lower rate of standard or routine metabolism, compared with more homozygous individuals, although heterozygosity-dependent differences in feeding rate may also be involved. The present study examined the relationship between clearance rate in three salinity treatments (5,15, and 25%.) and multiple-locus heterozygosity at nine polymorphic allozyme loci in the clam Rangia cuneata (Sowerby). Clearance rates were determined by disappearance of an algal suspension from a flowing-water system. Allozyme genotypes were determined using starch-gel electrophoresis. The polymorphic loci examined were those coding for a nonspecific esterase (Est), mannosephosphate isomerase (Mpi), leucine aminopeptidase (Lap), 6-phosphogluconate dehydrogenase (6-Pgd), phosphoglucose isomerase (Pgi), isocitrate dehydrogenase (Idh), malate dehydrogenase (Mdh), adenylate kinase (Adk), and phosphoglucomutase (Pgm). Weight-corrected clearance rates increased significantly (P < 0.05) with increasing multiple-locus heterozygosity and decreased significantly (P < 0.05) with increasing salinity. These data support the idea that heterozygosity-growth correlations may be due in part to differences in clearance rate. However, further study is needed to understand the exact physiological processes which relate heterozygosity and growth.     

Phenotypic plasticity for life history traits in Drosophila melanogaster. I. Effect on phenotypic and environmental correlations

All 36 possible crosses among 6 homozygous lines of Drosophila melanogaster were tested for their phenotypic response in developmental time and dry weight at eclosion to variation in temperature and yeast concentration. This method was chosen because it allows one to produce the same heterozygous offspring repeatedly for testing under more conditions than could be handled at once. We estimated the effects of yeast concentration and temperature and their interaction on both the phenotypic and the environmental components of variation and covariation of the two traits. Development was slower at low temperatures and yeast concentrations, and dry weight and viability were lower at higher temperatures and lower yeast levels. Interactions of the two factors with the crosses and with each other indicated that there were genetic differences in plasticity and that the sensitivity of a trait to one factor depended on the level of the other. The covariation of the two traits was generally weak within an environment. Across environments, its sign depended on the factor that changed between the environments: positive for temperature, negative for yeast concentration. These findings can be explained in terms of an established growth model for Drosophila larvae. We conclude that for plastic traits with moderate or low heritability, the relationship between the phenotypic and genetic covariance matrices may be a complex function of the environmental factors that affect the traits. Some implications for the prediction of the evolution in fluctuating environments are outlined.     

Enzyme function and polymorphism: A test in two Anolis lizard species

Electrophoretic surveys of two lizard species were used to test hypotheses that relate levels of enzyme variability to enzyme function (single-substrate versus multiple-substrate enzymes, regulatory versus nonregulatory enzymes). Anolis roquet behaviorally regulates its body temperature, but its congener A. gundlachi is passive to variations in the thermal environment. As a result, populations of A. gundlachi probably experience the thermal environment as temporally coarse-grained, whereas populations of A. roquet do not. We therefore predicted that A. gundlachi would exhibit greater enzyme heterozygosity than A. roquet and that different enzyme classes would contribute disproportionately to this interspecific difference. The data show (1) that A. gundlachi does have a higher heterozygosity and (2) that this difference appears to result from high levels of heterozygosity at loci coding for multiple-substrate enzymes. The dichotomy between regulatory and nonregulatory enzymes offers no explanation for the variability in heterozygosity among enzyme loci in these species.E.Z. was supported by a grant from the Natural Sciences and Engineering Council of Canada. The study was accomplished while P.E.H. held a postdoctoral fellowship from the Killam Trust of Dalhousie University and a grant from the Research Development Fund of Dalhousie University. The collection of material was made possible by grants (to P.E.H.) from National Science Foundation (DEB 75-16334), the Explorers Club of New York, Sigma Xi, and the Richmond and Anderson Funds of Harvard University. We thank Dr. D. W. Foltz for his help with the calculations.     

Genetic variation in populations of the arctic perennial Pedicularis dasyantha (Scrophulariaceae), on Svalbard,Norway

Isozyme variability was examined in 13 geographically isolated populations of the endemic arctic hairy lousewort (Pedicularis dasyantha) in the Svalbard Archipelago, 80° N latitude, Norway. Of the 23 enzyme systems screened on five buffer systems 18 were interpretable. Of the 31 reliable loci, only 6-phosphogluconate dehydrogenase (6-Pgd), was polymorphic. However, no heterozygotes were detected. Frequencies for allele 1 among the populations varied from 1.00 in the north to 0.00 in the south and 0.53 in the central “overlap” region. At the species level the mean number of alleles per locus (A) was 1.03. Percentage of polymorphic loci (P) was 3%. Expected heterozygosity (H_e) was 0.016. At the population level the mean number of alleles per locus was 1.01, and 1.1% of the loci were polymorphic. H_e was 0.004. These values are low compared to endemic, widespread, selling, and outcrossed species. Flower color morphs were distinct. They varied within and among the 13 populations. The frequency of color morphs coincided with allele frequencies of 6-PGD: allele 1 was found in dark purple morphs, and allele 2 was found in light morphs. This species shows more isozyme genetic variability than the five other species reported in the genus but generally less variation than other species with limited regional distributions. Low-level genetic variation in this diploid species may be a result of colonization events coupled with genetic drift, founder effects, and strong natural selection. Additional factors include the self-compatible reproductive system and the long-lived perennial habit.