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F W Allendorf

Publications and source records attributed to F W Allendorf.

At least 37 records · Page 2Linked to original sources
PubMed1986

Does enzyme heterozygosity influence developmental rate in rainbow trout?

The association between genetic variation at 14 enzyme loci and developmental rate was examined in six strains of rainbow trout (Salmo gairdneri). The purpose of this study was to test the prediction that heterozygotes develop faster than homozygotes. We also tested whether the enzyme loci could be responsible for such an association or are marking chromosomal segments that influence developmental rate. There is a significant negative association (P less than 0.05) between hatching time and the number of heterozygous loci per fish in one of six strains. Heterozygotes developed faster than homozygotes at 26 out of 43 possible comparisons made at individual loci within strains. Heterozygotes developed significantly faster than homozygotes in eight comparisons, and significantly slower in six comparisons. These results suggest a weak positive association between developmental rate and heterozygosity. Nine loci were polymorphic in more than one strain. At five of these loci the hatching distributions of heterozygotes and homozygotes are significantly different among strains. The direction of the relationship between heterozygosity and developmental rate at individual loci is not consistent among strains. Therefore, our results suggest that the loci surveyed are marking chromosomal segments that influence developmental rate. Linkage disequilibrium between alleles at the isozyme loci and dominant-acting genes that accelerate or retard developmental rate is hypothesised to account for the observed relationship between heterozygosity and developmental rate.

Aging↗
PubMed1985

Absence of developmental incompatibility in hybrids between rainbow trout and two subspecies of cutthroat trout.

We examined the developmental rate of hybrids between rainbow trout (Salmo gairdneri) and two subspecies of cutthroat trout: westslope cutthroat trout (Salmo clarki lewisi) and Yellowstone cutthroat trout (Salmo clarki bouvieri). These taxa show considerable genetic divergence at 42 structural loci encoding enzymes; the mean Nei's D between the rainbow trout and the two species of cutthroat trout is 0.22. We used four measures of developmental rate: time of hatching and yolk resorption, rate of increase in activity of four enzymes, and time of initial detection of seven isozyme loci. The two cutthroat trout subspecies reached hatching and yolk resorption earlier than rainbow trout. Cutthroat trout had higher relative enzyme activities than rainbow trout from deposition of eye pigment to hatching. There was no difference in the rate of increase in enzyme activity or time of initial expression of these loci between these species. Hybrids showed developmental rates intermediate or similar to that of the parental species using all measures. Our results indicate an absence of regulatory and developmental incompatibility between these taxa.

Age Factors↗
PubMed1985

Heterozygosity and developmental stability in gynogenetic diploid and triploid rainbow trout.

We have previously reported that rainbow trout (Salmo gairdneri) more heterozygous at enzyme loci generally show increased developmental stability, as measured by reduced fluctuating asymmetry. We experimentally produced gynogenetic diploid and triploid individuals to test the effect of extreme heterozygosities on developmental stability. Gynogenetic diploids are identical by descent at an estimated 34 per cent of all loci and show a 50 per cent increase in the mean proportion of traits asymmetric per individual compared to normal rainbow trout. Triploids from two different strains have an estimated 30 per cent increase in genomic heterozygosity and a 14 per cent decrease in the mean proportion of traits asymmetric per individual compared to normal diploids. These changes in asymmetry induced by gynogenesis and triploidy are not as great as we expected based on the association between heterozygosity and fluctuating asymmetry in random mating populations. The narrow range of mean asymmetry in rainbow trout may result from an upper limit restricted by directional selection for developmental stability and a lower limit determined by inherent randomness in the developmental process.

Animals↗
PubMed1985

Introgression between two cutthroat trout subspecies with substantial karyotypic, nuclear and mitochondrial genomic divergence.

The authors used allozymes encoded by nuclear genes and restriction enzyme analysis of mitochondrial DNA (mtDNA) to study secondary contact between westslope (Salmo clarki lewisi) and Yellowstone cutthroat trout (Salmo clarki bouvieri) in Forest Lake, Montana. Eleven diagnostic allozyme loci identified this as a random-mating hybrid swarm. No parental, first-generation hybrid or backcross genotypes were detected in the sample (N = 33), and genotype distributions at all the variable loci conform to binomial expectations. There is little linkage disequilibrium between the diagnostic loci, indicating that the nuclear genomes of the two subspecies are largely randomly associated. The allozymes and mtDNA give identical estimates of the proportional genetic contribution of each subspecies. Thus, males and females from both subspecies have contributed equally to this hybrid swarm. Although these subspecies have accumulated substantial genetic divergence between their nuclear (Nei's D = 0.34) and mitochondrial (2% sequence divergence) genomes, this has not resulted in a genetic barrier to exchange between them.

Alleles↗
PubMed1984

Major morphological effects of a regulatory gene: Pgm1-t in rainbow trout.

We have investigated the morphological effects of a genetic locus, Pgm1-t, that affects the expression of a phosphoglucomutase locus (Pgm1) in liver of rainbow trout (Salmo gairdneri). We have previously shown that embryos with liver Pgm1 expression hatch earlier than those without liver Pgm1 expression. We predicted that this difference in developmental rate should cause a reduction in meristic counts in the more rapidly developing fish with liver Pgm1 expression. Eight meristic (countable) characters in nine full-sib groups segregating for the presence or absence of liver Pgm1 expression are in agreement with this prediction. In eight of the nine families, there is a significant difference in the multivariate distribution of the eight meristic counts between full sibs with and without liver Pgm1 expression. This separation in multivariate space is based on a tendency for lower meristic counts in fish with liver Pgm1 expression. The magnitude of these morphological differences is similar to that between two subspecies of cutthroat trout (Salmo clarki) that show substantial genetic divergence at structural loci encoding enzymes (Nei's D = 0.34). These data support the view that small changes in the developmental process caused by genetic differences at regulatory genes can have large effects on morphology.

Animals↗
PubMed1984

Silencing of duplicate genes: a null allele polymorphism for lactate dehydrogenase in brown trout (Salmo trutta).

A previously described isozyme polymorphism at one of two skeletal muscle LdhA loci in brown trout is due to a null allele, Ldh1(n), producing no detectable catalytic activity. Homozygotes for this allele have approximately only 56% of the LDH activity in skeletal muscle relative to homozygotes for the active allele. The remaining activity results from enzyme subunits produced by other LDH loci. The Ldh1(n) allele is common and widespread throughout brown trout populations in Sweden and is also found in populations from Ireland. The persistence of duplicate gene expression for the LdhA loci in almost all salmonid species is best explained by natural selection against individuals containing null alleles. However, there is no indication of natural selection against brown trout with the Ldh1(n) allele: We suggest that the selection against individuals containing null alleles that is apparently responsible for the persistence of duplicate LdhA loci in salmonids occurs only under certain environmental conditions.

Alleles↗
PubMed1983

Developmental stability and enzyme heterozygosity in rainbow trout.

The developmental pathways of organisms are genetically adjusted to produce the characteristic morphology of the species regardless of variations in internal and external conditions during development. This 'developmental buffering', however, is not always precise. Bilateral characters of an organism are often asymmetric, that is, different in size, shape or number. Fluctuating asymmetry occurs when the difference between a character on the left and right sides of individuals is normally distributed about a mean of zero. This type of asymmetry results from the inability of an organism to develop precisely along determined paths and can be used as a measure of developmental stability. Increased developmental stability would be reflected by reduced amounts of fluctuating asymmetry. We have now examined the relationship between the amount of fluctuating asymmetry for five bilateral characters and heterozygosity at 13 polymorphic loci in a population of rainbow trout (Salmo gairdneri). Our results indicate a significant negative correlation between the proportion of heterozygous loci and the proportion of asymmetric characters. These data provide evidence that individuals with greater heterozygosity within a population have increased developmental stability.

Animals↗
PubMed1983

Adaptive significance of differences in the tissue-specific expression of a phosphoglucomutase gene in rainbow trout.

We have investigated the phenotypic effects of a mutant allele that results in the expression of a phosphoglucomutase locus (Pgm1) in the liver of rainbow trout. Embryos with liver Pgm1 expression hatch earlier than embryos without liver Pgm1 expression. These differences apparently result from increased flux through glycolysis in embryos with liver PGM1 activity while they are dependent on the yolk for energy. Fish with liver PGM1 activity are also more developmentally buffered, as indicated by less fluctuating asymmetry of five bilateral meristic traits. The more rapidly developing individuals begin exogenous feeding earlier and achieve a size advantage that is maintained until sexual maturity. This size advantage produces a significant tendency for earlier age of sexual maturity. These results show that different genotypes at this regulatory gene result in important phenotypic differences that are likely to be of important adaptive significance.

Age Factors↗
PubMed1983

Structural and regulatory variation of phosphoglucomutase in rainbow trout.

The results of inheritance experiments with allozymic variants indicate that two pairs of duplicate loci encode PGM in rainbow trout. Two of the loci (Pgm-3,4) share five electromorphs and are highly polymorphic. The large number of phenotypes and instability of these isozymes make them difficult to score in population studies. The other pair of duplicate loci (Pgm1 and Pgm2) have diverged both structurally and in their patterns of tissue-specific expression. We have detected four electromorphs at Pgm2; this locus is expressed approximately equally in all tissues examined. Two electromorphs and a null allele have been detected at Pgm1. PGM1 activity is greatest in skeletal muscle, heart, and brain; only weak activity, if any, is detectable in liver, eye, stomach, and kidney. Ten percent of the trout from the Arlee strain have a greater than 100-fold increase in the expression of Pgm1 in the liver but have normal expression of this locus in other tissues. Results of genetic crosses are consistent with a single regulatory gene (Pgm1-t) with additive inheritance being responsible for the differences in liver PGM1 activity. The allele responsible for the expression PGM1 in the liver is rare in rainbow trout and is apparently a recent mutation. The presence of PGM1 liver activity has a variety of phenotypic effects that are likely to be of adaptive significance. Embryos with liver PGM1 activity develop more quickly than their full-sibs lacking activity. This difference apparently results from increased flux through glycolysis in embryos with liver PGM1 activity while they are dependent on the yolk for energy. The more rapidly developing individuals begin exogenous feeding earlier and obtain a size advantage that is maintained until sexual maturity. This size advantage also produces a tendency for earlier age of first sexual maturity. Fish with liver PGM1 activity are also more developmentally buffered, as indicated by less fluctuating asymmetry of five meristic traits.

Alleles↗
PubMed1982

Identification of a gene regulating the tissue expression of a phosphoglucomutase locus in rainbow trout.

Nine percent of the rainbow trout (Salmo gairdneri) from a hatchery source have a greater than 100-fold increase in expression of a phosphoglucomutase (PGM) locus, Pgm1, in the liver but have normal expression of this locus in other tissues. The results of genetic crosses are consistent with a single regulatory gene with additive inheritance being responsible for the differences in the amount of PGM activity in the liver.--The allele responsible for the expression of Pgm1 in the liver is apparently a recent mutation. This is supported by its restricted distribution in rainbow trout and the absence of liver Pgm1 expression in closely related species. This genetic system is valuable for future analysis of the control of gene expression and in determining the relative evolutionary importance of genetic variation at structural and regulatory genes.

Animals↗
PubMed1979

Inheritance of isozyme variation and heterozygosity in Pinus ponderosa.

Techniques are presented to detect 23 isozyme loci in the long-lived perennial plant, ponderosa pine. Meiotically derived megagametophyte from seeds is used to examine directly the segregation of allelic variants. Approximately seven seeds were initially examined for 12 enzymes from each of 47 trees from ten stands throughout the northern Rocky Mountain region. Additional seeds were also examined from selected families to confirm the inheritance of observed electrophoretic variants at 13 polymorphic loci and to estimate linkage relationship. Significant norandom segregation was consistently detected for three pairs of loci: ADH-1:AAT-2, ADH-1:PGI-1, and LAP-2:6PG-1. Preliminary estimates of population parameters reveal a relatively high average heterozygosity (H = 0.123). This is partitioned into a high amont of genetic variation within local stands, with only approximately 12% of the total heterozygosity resulting from genic difference between stands.

Gene Frequency↗
PubMed1979

Genetic basis of creatine kinase isozymes in skeletal muscle of salmonid fishes.

The genetic basis of isozyme phenotypes of creatine kinase (CK) from extracts of skeletal muscle of salmonids has been resolved through breeding data including double heterozygous crosses and backcrosses of rainbow trout (Salmo gairdneri), and backcrosses of coho salmon (Oncorhynchus kisutch). The two-three-, or four-banded phenotypes of homozygous individuals and all heterozygous and hybrid phenotypes of ten salmonid species are readily explained by the following model: (1) there are no detectable heterodimers either between allelic products at a single locus or between loci: (2) each allele is represented electrophoretically by two bands, presumably a reflection of stable posttranslational modification of a single polypeptide unit; (3) CK of salmonid muscle is encoded by two loci--CK-1 and CK-2. The distance separating the paired bands reflecting each allele provides a basis for two groupings--a broad-spaced group (including all species of Oncorhynchus tested excepting O. masou) and a narrow-spaced group (including all species of Salmo tested and O. masou). The relationships among species suggested by the relative mobilities and spacings of these CK bands are consistent with taxonomic schemes inferred from morphological, cytogenetic, and other isozymic data.

Animals↗
PubMed1979

Reproductive isolation with little genetic divergence in sympatric populations of brown trout (Salmo trutta).

Two reproductively isolated demes of brown trout coexist in a small Swedish mountain lake, Lake Bunnersjörna. We electrophoretically examined 102 specimens from that lake for 27 enzymes encoded by 54 loci. The two demes are fixed for different alleles at a lactate dehydrogenase locus (LDH-1); statistically significant allele frequency differences at five other loci further support the complete lack of gene flow between these demes. There are significant differences in growth rates between fish in the two demes, but no further morphological differentiation h-s been detected.--In light of these findings, the genetic distance between these populations is surprisingly small (Nei's I = 0.975). These demes represent one of the least genetically divergent, reproductively isolated sympatric pair of vertebrate populations that have been identified. The results are discussed from both an evolutionary and ecological perspective.

Alleles↗