Genetic variation and population structure of cod, Gadus morhua L., in some fjords in northern Norway

Biochemical genetic polymorphism in cod from several fjords in Troms, northern Norway was analysed. Gene frequencies at several polymorphic loci ( Hb, Pgi, Ldh, Pgm, Gpd and Idh ) are given. Significant variation was found both within and between fjords, and even between samples from the same locality sampled in different years, indicating a mosaic structure of the cod population in the area studied. The results of the haemoglobin variation are compared to similar results obtained more than 20 years ago in the same and adjacent areas. The biochemical genetic variation is discussed in relation to stability of gene frequencies, isolation mechanisms and migration patterns.     

Partial characterization of the trait for enhanced K+−Na+ discrimination in the D genome of wheat

The long arm of chromosome 4D of wheat (Triticum aestivum L.) contains a gene (or genes) which influences the ability of wheat plants to discriminate between Na⁺ and K⁺. This discrimination most obviously affects transport from the roots to the shoots, in which less Na⁺ and more K⁺ accumulate in those plants which contain the long arm of chromosome 4D. Concentrations of Na⁺ and K⁺ in the roots, and Cl⁻ concentrations in the roots and shoots, are not significantly affected by this trait, but Na⁺, K⁺ and Cl⁻ contents of the grain are reduced. The trait operates over a wide range of salinities and appears to be constitutive. At the moment it is not possible to determine accurately the effect of this trait on growth or grain yield because the aneuploid lines which are available are much less vigorous and less fertile than their euploid parents.     

Transformed plants with elevated levels of chloroplastic SOD are not more resistant to superoxide toxicity

The petunia nuclear gene which encodes the chloroplast isozyme of superoxide dismutase, SOD-1, has been fused with an efficient rbcS promoter fragment and 3 flanking region and introduced into tobacco and tomato cells. Transformed plants carrying this chimeric gene have up to 50-fold the levels of SOD-1 which occur in wild-type plants. However, tobacco plants with 30-to 50-fold the normal SOD-1 activity do not exhibit resistance to the light-activated herbicide paraquat. Similarly, tomato plants with 2-to 4-fold increases in SOD-1 do not exhibit tolerance to photoinhibitory conditions known to increase superoxide levels (high light, low temperatures and low CO₂ concentrations). Our data indicate that increasing the chloroplastic SOD level in a plant cell is not sufficient to reduce the toxicity of superoxide.     

Restriction Enzyme Analysis of Mitochondrial DNA of Acanthamoeba Strains in Japan

ABSTRACT. Eight isolates, identified as either Acanthamoeba castellanii or A. polyphaga from human eye infections, contact lens containers, and soil in Japan, were characterized by restriction fragment length polymorphisms (RFLP) of mitochondrial DNA (mtDNA). Mitochondrial DNA was digested with either Bgl II, Eco R I, Hind III, Hpa I, Sca I or Xba I, electrophoresed in agarose gels, and stained with ethidium bromide. Four distinct RFLP phenotypes that refer to the collection of six fragment size patterns obtained for a single strain with six enzymes, were discovered among the eight strains used in this study. Three strains morphologically classified as A. polyphaga share a single RFLP phenotype with the Ma strain of A. castellanii. The interspecific sequence differences of 7.06–12.74% in DNA nucleotide were estimated from the proportion of DNA fragments shared by each pair of mtDNA.     

QUANTITATIVE GENETICS OF SPRINT RUNNING SPEED AND SWIMMING ENDURANCE IN LABORATORY HOUSE MICE (MUS DOMESTICUS)

We tested the hypothesis that locomotor speed and endurance show a negative genetic correlation using a genetically variable laboratory strain of house mice (Hsd:ICR: Mus domesticus). A negative genetic correlation would qualify as an evolutionary “constraint,” because both aspects of locomotor performance are generally expected to be under positive directional selection in wild populations. We also tested whether speed or endurance showed any genetic correlation with body mass. For all traits, residuals from multiple regression equations were computed to remove effects of possible confounding variables such as age at testing, measurement block, observer, and sex. Estimates of quantitative genetic parameters were then obtained using Shaw's (1987) restricted maximum-likelihood programs, modified to account for our breeding design, which incorporated cross-fostering. Both speed and endurance were measured on two consecutive trial days, and both were repeatable. We initially analyzed performances on each trial day and the maximal value. For endurance, the three estimates of narrow-sense heritabilities ranged from 0.17 to 0.33 (full ADCE model), and some were statistically significantly different from zero using likelihood ratio tests. The heritability estimate for sprint speed measured on trial day 1 was 0.17, but negative for all other measures. Moreover, the additive genetic covariance between speeds measured on the two days was near zero, indicating that the two measures are to some extent different traits. The additive genetic covariance between speed on trial day 1 and any of the four measures of endurance was negative, large, and always statistically significant. None of the measures of speed or endurance was significantly genetically correlated with body mass. Thus, we predict that artificial selection for increased locomotor speed in these mice would result in a decrease in endurance, but no change in body mass. Such experiments could lead to a better understanding of the physiological mechanisms leading to trade-offs in aspects of locomotor abilities.     

FIXATION PROBABILITIES OF SELFING RATE MODIFIERS IN SIMULATIONS WITH SEVERAL DELETERIOUS ALLELES WITH LINKAGE

The fixation rates of selfing rate modifiers were found by stochastic simulation in an infinite site model, including effects of several deleterious alleles with variable effects, which were randomly distributed in the genome without assuming any pollen discounting. Previous results on the evolution of selfing obtained by more precise methods were in this study further validated, and it was concluded that the effect of genetic associations on the evolution of mating systems is small except in the case of full pollen discounting. Furthermore, attention was given to the uneven distribution of the genetic load in the population, and the accompanying large among-genome variation in fixation rates. This among-genome variation will be of significance for the evolution of mating systems.     

EVOLUTION OF FLORAL TRAITS IN A HERMAPHRODITIC PLANT: FIELD MEASUREMENTS OF HERITABILITIES AND GENETIC CORRELATIONS

Genetic variances, heritabilities, and genetic correlations of floral traits were measured in the monocarpic perennial Ipomopsis aggregata (Polemoniaceae). A paternal half-sib design was employed to generate seeds in each of four years, and seeds were planted back in the field near the parental site. The progeny were followed for up to eight years to estimate quantitative genetic parameters subject to natural levels of environmental variation over the entire life cycle. Narrow-sense heritabilities of 0.2–0.8 were detected for the morphometric traits of corolla length, corolla width, stigma position, and anther position. The proportion of time spent by the protandrous flowers in the pistillate phase (“proportion pistillate”) also exhibited detectable heritability of near 0.3. In contrast, heritability estimates for nectar reward traits were low and not significantly different from zero, due to high environmental variance between and within flowering years. The estimates of genetic parameters were combined with phenotypic selection gradients to predict evolutionary responses to selection mediated by the hummingbird pollinators. One trait, corolla width, showed the potential for a rapid response to ongoing selection through male function, as it experienced both direct selection, by influencing pollen export, and relatively high heritability. Predicted responses were lower for proportion pistillate and corolla length, even though these traits also experienced direct selection. Stigma position was expected to respond positively to indirect selection of proportion pistillate but negatively to selection of corolla length, with the net effect sensitive to variation in the selection estimates. Anther position also was not directly selected but could respond to indirect selection of genetically correlated traits.     

A TRADE-OFF FOR HOST PLANT UTILIZATION IN THE BLACK BEAN APHID,APHIS FABAE

Many studies on insect herbivores have sought to find trade-offs between utilization of alternate host plants, both to understand the prevalence of specialization and to appreciate the likelihood of sympatric speciation due to disruptive selection. To date, few studies have found trade-offs. Seventy-seven clones of the black bean aphid, Aphis fabae, were collected from field sites in East Anglia, U.K., over an area of about 10,000 km². These clones exhibit a trade-off in fitness between two alternative hosts, broad bean and nasturtium. This pattern is maintained in the F2 generation. The predominance of broad bean in the area, the fact that clones were only sampled from one of these two hosts, and the absence of “master-of-all-trades” genotypes after recombination all point to the importance of antagonistic pleiotropy rather than linkage disequilibrium in maintaining this trade-off. It is concluded that this population presents strong evidence for a fundamental trade-off for host utilization.     

Isozyme analysis of Galaxias species (Teleostei: Galaxiidae) from the Taieri River, South Island, New Zealand: a species complex revealed

We examined genetic differentiation among 23 samples of non-migratory river galaxias from 17 streams in the Taieri River system, South Island, New Zealand. Four major genetic types were found, two of which occur in narrow sympatry in one location. These were compared with topotypical material representing Galaxias anomalus from the Clutha system (Otago) and G. vulgaris from the Waimakariri system (Canterbury) in order to establish identity. Morphological examination of these four major genetic types revealed consistent concomitant differences. The results suggest that there are at least three species of river galaxias in the Taieri system: G. anomalus, G. vulgaris and at least one previously undescribed species. We propose that the genetic structuring and subsequent speciation of this group has been promoted by the absence of the marine juvenile phase that is found in five other members of the genus native to New Zealand. This structuring may be exacerbated by population fragmentation over the last century owing to the negative influence of introduced trout. The phylogenetic diversity within the river system mirrors the diverse flora and invertebrate fauna of the region, and has conservation implications that parallel those resulting from our improved knowledge of the New Zealand herpetofauna through the application of genetic analysis.     

The extended replicator

This paper evaluates and criticises the developmental systems conception of evolution and develops instead an extension of the gene's eye conception of evolution. We argue (i) Dawkin's attempt to segregate developmental and evolutionary issues about genes is unsatisfactory. On plausible views of development it is arbitrary to single out genes as the units of selection. (ii) The genotype does not carry information about the phenotype in any way that distinguishes the role of the genes in development from that other factors. (iii) There is no simple and general causal criterion which distinguishes the role of genes in development and evolution. (iv) There is, however, an important sense in which genes but not every other developmental factor represent the phenotype. (v) The idea that genes represent features of the phenotype forces us to recognise that genes are not the only, or almost the only, replicators. Many mechanisms of replication are involved in both development and evolution. (vi) A conception of evolutionary history which recognises both genetic and non-genetic replicators, lineages of replicators and interactors has advantages over both the radical rejection of the replicator/interactor distinction and the conservative restriction of replication to genetic replication.