Aadaptive lactate dehydrogenase variation in the crested blenny, Anoplarchus

BIOCHEMICAL GENETICS OF MOSQUITOFISH. IV. CHANGES OF ALLELE FREQUENCIES THROUGH TIME AND SPACE

Gene frequency data from samples of Gambusia affinis populations at 76 localities across the Savannah River drainage were used to investigate temporal and spatial patterns in population genetic structure. Localities in the Par Pond system on the Savannah River Plant were sampled in 1971, 1977, and 1979. Allelic frequencies in these populations were generally stable through time, although significant temporal changes were observed among samples from Pond C, an impoundment receiving thermal effluent. Significant spatial heterogeneity in allele frequencies was observed on both microgeographic and regional scales. Populations within the Par Pond system were spatially subdivided at four of the five loci surveyed (mean F_ST = 0.051). Subdivision was even more pronounced when samples from across the Savannah River drainage were compared (mean F_ST = 0.196). A hierarchial analysis of gene diversity (G_ST ) demonstrated that most of the genic diversity across the drainage exists as within-subdivision diversity. Even when populations from such contrasting habitats as rivers, creeks, ponds, and reservoirs are compared, an average of only 13% of the total gene diversity was attributed to between-group diversity. Greatest between-group gene diversity was observed when reservoirs were compared with one another. This general pattern of low between-habitat diversity suggests that differential selection pressures are not playing a major role in producing the observed levels of subdivision. In the Par Pond system, neither single locus nor multilocus genetic distances were significantly associated with geographic distance or with its reciprocal. For samples from over the Savannah River drainage, significant correlations between genetic and geographic distance were observed only for the Gpi-2 and Pgm-2 loci. Thus, there was a general lack of concordance between genetic and geographic distances. Spatial autocorrelation demonstrated patterns consistent with Wright's isolation by distance model. Significant positive correlations in allelic frequencies among neighboring populations were observed for five of six alleles; allelic frequencies in more distantly separated populations were typically not correlated.

Electrophoretic variation in intertidal and subtidal organisms in Puget Sound, Washington

This paper presents information on the biochemical properties (via starch gel electrophoresis) of 26 marine species (15 fish and 11 invertebrates). Evidence is presented on 48 polymorphisms found in the 26 species. Estimates of the proportion of the genome heterozygous per individual per species were calculated and ranged from 0.000 to 0.176 for the invertebrates and from 0.000 to 0.074 for the fish species. Estimates of the percentage of loci polymorphic per species for invertebrates were 0 to 54%; for the fish species, the range was 0 to 20%.

Nongenetic variation, genetic-environmental interactions and altered gene expression. I. Temperature, photoperiod, diet, pH and sex-related effects

The use of protein electrophoretic data for determining the relationships among species or populations is widespread and generally accepted. However, many confounding factors may alter the results of an electrophoretic study in such a way as to allow erroneous conclusions to be drawn in taxonomic, systematic or population studies. Such variables as temperature, photoperiod, salinity, pH and diet have been shown to influence enzymes and proteins both quantitatively and qualitatively. Production of distinct "cold" and "warm" isozymes or "seasonal" isozymes have been found in a variety of organisms. The factors that are or may be responsible for the appearance of these isozymes is discussed. Most studies that have demonstrated some apparent form of environmentally induced genetic expression have not determined that mechanisms responsible. However, proteolytic modification has been shown to produce seasonal isozymes of fructose 1,6-bisphosphatase in rabbit liver and may account for other seasonal isozymes. Acclimating organisms to various conditions may actually allow detection of cryptic genetic variation and provide valuable data. There are many aspects to consider in designing acclimation experiments, and the conditions used will vary according to the aim of the research. Polyploidy may contribute to the genesis of environmentally regulated isozymes. A review of this literature follows with additional hypotheses and conclusions. Recommendations are given for the resolution of real and potential problems.

Influence of amylase genotypes on growth rate and feed conversion of chickens

Chickens from two breeds were screened for amylase alleles designated as AmyF and AmyS to establish breeder flocks homozygous for each. Offspring from these flocks were then used to test the hypothesis that AmyF and AmyS amylases differ in their ability to digest cornstarch and wheat starch. The amylase allozymes were found to affect growth and feed conversion performance of the chickens, and the effects were more pronounced in one breed. However, these effects seemed to be more related to specific activity of the amylases than to starch source in the diet. The results indicate that in some breeds of chickens selection for AmyS may improve growth and feed efficiency performance.

Temperature-dependent genotypic selection and embryonic survival of rainbow trout

The survival of rainbow trout (Salmo gairdneri) with different developmental rates and genotypes at eight polymorphic loci was compared in two experiments. The embryos were reared at temperatures colder (5 and 8 degrees C) and warmer (12 degrees C) than normally experienced by the strain (9.5 degrees C). Embryo survival in five different hatching groups (representing the sequential order of hatching) was compared at 8 and 12 degrees C. Embryos in the center of the hatching distribution (groups 2, 3, and 4) showed a greater survival to yolk sac resorption than those in the extremes (groups 1 and 5). These differences are significant in the embryos reared at 12 degrees C in both experiments. Embryo survival from hatching to yolk sac resorption was poorer at 12 compared to 8 degrees C. In the one experiment where it was examined, significantly fewer embryos hatched at 5 and 12 than at 8 degrees C. Significant deviations from genotypic expectations (based upon parental allele frequencies) were detected in the progeny (23 of 34 cases). In contrast, few deviations from Hardy-Weinberg expectations were detected (5 of 34 cases) when progeny allele frequencies are used. Few significant differences in genotype frequencies were detected among the progeny reared at the different temperatures. This suggests that nonequal contributions of parental gametes rather than differential selection of genotypes account for the deviations from expectations in the progeny.

Physiological effects of an allozyme polymorphism: glutamate-pyruvate transaminase and response to hyperosmotic stress in the copepod Tigriopus californicus

In order to regulate cell volume during hyperosmotic stress, the intertidal copepod Tigriopus californicus, like other aquatic crustaceans, rapidly accumulates high levels of intracellular alanine, proline, and glycine. Glutamate-pyruvate transaminase (GPT; EC 2.6.1.2), which catalyzes the final step of alanine synthesis, is genetically polymorphic in T. californicus populations at Santa Cruz, California. Spectrophotometric studies of homogenates derived from a homozygous isofemale line of each of the two common GPT alleles indicated that the GPTF allozyme has a significantly higher specific activity than the GPTS allozyme. Under conditions of hyperosmotic stress, individual adult copepods of GPTF and GPTF/S genotypes accumulated alanine, but not glycine or proline, more rapidly than GPTS homozygotes. When young larvae were subjected to the same hyperosmotic conditions, GPTS larvae suffered a significantly higher mortality than GPTF or GPTF/S larvae. These results suggest that the biochemical differences among GPT allozymes result in specific physiological variation among GPT genotypes and that this physiological variation is manifested in differential genotypic survivorships under some naturally occurring environmental conditions.

Biochemical genetics of Fundulus heterolitus (L.). I. Temporal and spatial variation in gene frequencies of Ldh-B, Mdh-A, Gpi-B, and Pgm-A

Natural populations of Fundulus heteroclitus show extensive spatial variation in gene frequencies at four unlinked polymorphic loci. Large clinal changes in gene frequencies were found for Ldh-B, Mdh-A, and Gpi-B, whereas the spatial variation for the Pgm-B locus was small. Since the geographical area over which these clines are found is characterized by a steep thermal gradient, the clines in gene frequency are correlated with a directional change in mean water temperature. Maximum gene diversity of these four loci was correlated with annual fluctuations in water temperature. Temporal stability of the allelic frequencies was established for a 2--4 year period.

Genetical composition, temperature, density and selection in an enzyme polymorphism

Selection in egg-to-adult viability was investigated at the Esterase-6 locus of Drosophila melanogaster. A factorial experiment was carried out with three variables, temperature, density and genetical composition; there were four temperatures (15 degrees, 20 degrees, 25 degrees and 30 degrees), three densities (115 ml, 10 ml and 2-5 ml of food). Strong frequency dependent selection was observed in many environments. The strength of the selection was very much modified by an interaction between temperature and density. The results are discussed in relation to evidence for a chemical mechanism which mediates frequency dependent selection, by conditioning, in the larval environment.

Genetic variation in irradiated and control populations of Cnemidophorus tigris (sauria, teiidae) from Mercury, Nevada with a discussion of genetic variability in lizards

Whiptail lizards (Cnemidophoms tigris) were collected from fenced irradiated, fenced control, and unfenced areas near Mercury Nevada. No changes in allele frequencies at 26 allozyme loci could be ascribed to irradiation or fencing. This species is the most polymorphic and heterozygous lizard so far examined. - Heterozygosity estimates derived from electrophoretic studies on 20 additional species of lizards are compared with Cnemidophorus. A general trend seems to emerge. Fossorial lizards have uniformly low levels of heterozygosity (ca. 1 %). Territorial "sit and wait" predators are intermediate (ca. 5%). Highly vagile apparently nonterritorial lizards are the most heterozygous (ca. 10%). Assuming that this trend does not reflect some of sampling error, two current, non-mutually exclusive hypotheses explain the observed situation: (1) the niche width variation hypothesis predicts, higher variability in populations where individuals are exposed to largescale environmental heterogeneity; and (2) the population size hypothesis predicts that, all other things being equal, vagility would tend to increase the effective population size by reducing inbreeding, which would promote higher levels of genetic variation.

Genetic analysis of enzyme polymorphisms in plaice (Pleuronectes platessa)

Genetic analysis was performed on five enzyme systems (G3PDH; GPI-A; GPI-B; PGM; MDH-A) in plaice (Pleuronectes platessa) collected in spawning condition from the North Sea. Conventional crosses, induced gynogenesis and induced triploidy were performed. The data conclusively demonstrated the inheritance of isozymes by co-dominant alleles at individual loci for each system. No linkage was observed but tests did not include MDH nor the possibility of linkage between G3PDH and GPI-A. Some anomalous segregation ratios were observed, particularly a deficiency of heterozygotes for GPI-A, but the data were largely in conformity with Mendelian expectations. At the PGM locus, five independent anomalous individuals were scored and interpreted as mutations with a mutation rate of 1.1 X 10(-3) per gamete. Recombination with the centromere was assessed and induced triploidy and cross-over values of 41 per cent for PGM, 19 per cent for MDH-A and 9 per cent for GPI-B were derived on the assumption of complete interference. Amongst the parent fish, genotypic and phenotypic frequencies were largely consistent with the expectations of the Hardy-Weinberg Law, and allelic frequencies were not significantly different between year of collection or location of collection ground.