Showing papers in "Heredity in 1987"
TL;DR: It is found that the heritability of morphological traits is significantly lower for ectotherms than it is for endotherms which may in part be a result of the strong correlation between life history and body size for many ectotherm.
Abstract: The hypothesis that traits closely associated with fitness will generally possess lower heritabilities than traits more loosely connected with fitness is tested using 1120 narrow sense heritability estimates for wild, outbred animal populations, collected from the published record. Our results indicate that life history traits generally possess lower heritabilities than morphological traits, and that the means, medians, and cumulative frequency distributions of behavioural and physiological traits are intermediate between life history and morphological traits. These findings are consistent with popular interpretations of Fisher's (1930, 1958) Fundamental Theorem of Natural Selection, and Falconer (1960, 1981), but also indicate that high heritabilities are maintained within natural populations even for traits believed to be under strong selection. It is also found that the heritability of morphological traits is significantly lower for ectotherms than it is for endotherms which may in part be a result of the strong correlation between life history and body size for many ectotherms.
1,483 citations
TL;DR: Pattern of heritability and genetic covariance between traits in the genus Drosophila supports the variable pleiotropy hypothesis but other factors such as environmental heterogeneity, or mutation cannot be excluded.
Abstract: This paper examines patterns of heritability and genetic covariance between traits in the genus Drosophila. Traits are divided into the categories, morphology, behaviour, physiology and life history. Early theoretical analyses suggested that life history traits should have heritabilities that are lower than those in other categories. Variable pleiotrophy, environmental variation, mutation and niche variation may, however, maintain high heritabilities. In Drosophila the heritabilities of life history traits are lower than morphological or physiological traits but may exceed 20 per cent. The pattern of variation in the heritability of behavioural traits is similar to that of life history traits. Genetic covariance between morphological traits and between morphological and life history traits are all positive but those between life history traits have variable sign. Negative covariance between traits supports the variable pleiotropy hypothesis but other factors such as environmental heterogeneity, or mutation cannot be excluded.
467 citations
TL;DR: The heredity of rover/sitter, a naturally occurring polymorphism in the locomotory component of Drosophila melanogaster third instar larval foraging behaviour, was analysed by comparing 16 reciprocal crosses made using isogenic rover and sitter parental strains and indicated that rover/Sitter differences have an autosomal basis.
Abstract: Heredity of rover/sitter: Alternative foraging strategies of Drosophila melanogaster larvae
168 citations
TL;DR: Many theoretical papers investigating the relationship between chromosomal change and speciation are found to have been based on erroneous data, and a new approach is suggested.
Abstract: Many theoretical papers investigating the relationship between chromosomal change and speciation are found to have been based on erroneous data. For rather than considering those negatively heterotic, or at least potentially negatively heterotic rearrangements which can have a possible role in speciation, these papers have included substantial amounts of information on rearrangements which are not implicated in this process. Common forms of chromosomal repatterning such as heterochromatic addition and polymorphism are in this category. Their inclusion in theoretical studies, often cited as supporting or opposing a chromosomal involvement in speciation, invalidates these findings. A new approach is suggested.
81 citations
TL;DR: It is proposed that the founding of populations on Jamaica by long-distance dispersal, genetic drift and high levels of self-fertilisation all contribute to reducing levels of genetic variation in Jamaican populations.
Abstract: Genetic variation in continental and island populations of Eichhornia paniculata (Pontederiaceae)
81 citations
TL;DR: Apparent random spatial heterogeneity is expected if gene flow is extensive enough to prevent a rapid decline in genetic correlation with distance; it also might be promoted by a leapfrog pattern of gene flow.
Abstract: Spatial genetic heterogeneity in a population of the montane perennial plant Delphinium nelsonii
78 citations
TL;DR: Haploid nuclear DNA of 23 species of Aedes, as determined by Feulgen cytophotometry, was found to vary 3-fold, accompanied by a 2-fold variation in total chromosomal length.
Abstract: Haploid nuclear DNA of 23 species of Aedes, as determined by Feulgen cytophotometry, was found to vary 3-fold. This was accompanied by a 2-fold variation in total chromosomal length. There was a significant correlation (r = 0·765, P<0·001) between these two parameters. Genome size varied from 0·87 pg to 1·3 pg among 10 strains of Aedes albopictus, from wide geographic regions. Large scale differences in chromosomal DNA amounts have accompanied speciation and evolution in aedine mosquitoes.
76 citations
TL;DR: Large-scale length variation has been described in a few other lower vertebrates, but some of the insertion variants within populations described here are of unprecedented size, in dramatic contrast to mammalian mtDNA in which size variation is largely restricted to small (<15 bp) insertions and deletions.
Abstract: Mitochondrial DNA insertion polymorphism and germ line heteroplasmy in the Triturus cristatus complex
75 citations
TL;DR: It is argued that the local differentiation results, in part, from a reduction in effective population sizes associated with the ephemeral nature of milkweed patches and that this population structure is favourable for the operation of Wright's Shifting Balance mode of evolution.
Abstract: Hierarchical population structure analysis of the milkweed beetle, Tetraopes tetraophthalmus (Forster)
72 citations
TL;DR: The relationship between pollination order and the transmission of male genes to seed was investigated by performing a large number of genetically marked, double and mixed artificial pollinations in the common morning glory, Ipomoea purpurea, and data indicate that gametophytic selection may be an important component of natural selection in Ip Pomoea.
Abstract: The relationship between pollination order and the transmission of male genes to seed was investigated by performing a large number of genetically marked, double and mixed artificial pollinations in the common morning glory, Ipomoea purpurea. Second pollinations were substantially less effective than first pollinations, even when applied immediately afterwards. When delayed 30 and 60 minutes, effectiveness was reduced further to about 14 and 7 per cent of fertilisations, respectively. After 120 minutes, effectiveness decreased to less than 2 per cent. Among a set of mixed pollinations, pollen from some individuals suffered a strong disadvantage in competitive ability. This disadvantage is partially genetic. The primacy of first pollinations, and the presence of strong pollen competition, have implications for studies of pollination biology and genetic transmission in natural populations of Ipomoea purpurea and other plant species. Specifically, sequential pollination ineffectiveness, and strong competition within pollen loads, should reduce the numbers of paternal parents and thus increase the numbers of full sibs among outcross seed within capsules. This represents a substantial violation of one of the critical assumptions in the mixed mating model and could influence the genetic structure of Ipomoea populations. In addition, these data indicate that gametophytic selection may be an important component of natural selection in Ipomoea. The mechanisms underlying the sequential and competitive effects probably include pollen-stigma interactions, differential pollen production, viability differences, or pollen tube growth rate differences, and possibly embryo abortion. These experiments also establish that outcrossing rates vary among individuals in natural populations, due to genetic variation in the distance between anthers and the stigmatic surface.
71 citations
TL;DR: Results support those presented previously based on simulated results and a positive control indicating that, for samples of this size, accurate estimates are derived by the maximum likelihood technique.
Abstract: 1691 F-2 progeny of a cross between Lycopersicon esculentum and L pimpinellifolium grown under field conditions were scored for 18 quantitative traits of economic interest and 10 segregating genetic markers. Each parental strain was homozygous for one allele of each marker. Four of the markers were electrophoretic, and six were morphological. Three pairs of the genetic markers were linked. An algorithm described previously based on maximum likelihood technique was used to estimate the parameters of loci affecting the quantitative traits linked to the genetic markers and the recombination distance between quantitative trait loci and marker loci. The parameters of quantitative trait loci linked to two genetic markers were also estimated by solving for gene effect and recombination frequency from the independent equations derived from each marker. In general there was close correspondence between estimates obtained from the two methods. Except for cases where highest likelihood was obtained at complete linkage, results of the approximate maximum likelihood technique were within the parameter space, i.e. recombination frequencies between zero and 0·5 and positive variance estimates. Unreasonable results were obtained when the assumptions of the method were violated. These results support those presented previously based on simulated results and a positive control indicating that, for samples of this size, accurate estimates are derived by the maximum likelihood technique. A genetic map of quantitative trait loci is presented.
TL;DR: A range of 4C DNA values from 41·19 pg to 142·78 pg was found, largely unrelated to basic chromosome number, polyploidy or taxonomic group, but correlated with flowering time, which is discussed in relation to distribution of DNA values in the genus.
Abstract: 4C nuclear DNA contents were determined for 42 Allium species, selected from all major taxonomic sections in the genus. Estimates of nuclear volumes were also made. A range of 4C DNA values from 41·19 pg to 142·78 pg was found, largely unrelated to basic chromosome number, polyploidy or taxonomic group, but correlated with flowering time. The results are discussed in relation to distribution of DNA values in the genus, proportions of chromosome C-banding, breeding systems and climatic adaptation.
TL;DR: Analysis of megagametophytic and embryonic allozyme variants in nine enzymatic systems encoded by 14 loci was conducted on 30 western white pine trees from a natural stand on Vancouver Island, B.C, indicating a major genetic shift between the two life-cycles phases and the implications of the apparent inbreeding on the derivation of genetic estimates.
Abstract: Allozyme inheritance, heterozygosity and outcrossing rate among Pinus monticola near Ladysmith, British Columbia
TL;DR: Despite the apparent genetic complexity of this behaviour, it was found that at least one locus affecting this preference is linked to the autosomal gene encoding the enzyme aconitase, thus encouraging the belief that it may eventually be possible to study the molecular and developmental basis for this evolutionarily important behaviour.
Abstract: A survey of 175 isofemale strains from seven populations of Drosophila tripunctata showed that the preferences of females for mushrooms versus tomatoes as oviposition sites follow an approximately normal distribution among strains, as would be expected if this behaviour were governed by many genes with small, additive effects. However, crosses among several strains revealed the existence of autosomal genes with dominance and interaction effects having substantial influence on oviposition-site preference. Despite the apparent genetic complexity of this behaviour, it was found that at least one locus affecting this preference is linked to the autosomal gene encoding the enzyme aconitase, thus encouraging the belief that it may eventually be possible to study the molecular and developmental basis for this evolutionarily important behaviour.
TL;DR: Evidence is presented that suggests the aberrant ratios arose from linkage of the markers with genetic factors affecting prezygotic transmission, and that a minimum of 5 such factors were operative, one on each of chromosomes 1, 2, 3, 6, and 8.
Abstract: Genetic segregation was studied in more than 1900 seedlings of an F2 between the maize (Zea mays L.) inbred lines T232 and CM37. Significant segregation distortion was observed at 11 of 17 segregating allozyme loci and at a single morphological marker locus distributed on 7 of the 10 chromosomes in the genome. Deviations from genotypic class expectations were small for most loci, and averaged 7·7 per cent. Percent transmission of the allele contributed by T232 varied from 47·7 per cent to 53·3 per cent. The allele donated by T232 was significantly under-represented for loci on chromosomes 1 and 8, whereas the allele contributed by CM37 was deficient for nine of the ten segregating loci on chromosomes 2, 3, and 6. In all cases, the parental origin of the deficient allele was consistent for markers on a chromosome. Evidence is presented that suggests the aberrant ratios arose from linkage of the markers with genetic factors affecting prezygotic transmission, and that a minimum of 5 such factors were operative, one on each of chromosomes 1, 2, 3, 6, and 8. In contrast to the multi-locus and multi-chromosomal distorted segregation observed in the F2, all loci in backcross progenies fit Mendelian expectations. It is suggested that this discrepancy reflects variable environmental selection pressures on genes that influence aspects of gamete competition.
TL;DR: The neighbourhood model of Wright is extended to enable estimates of σ2, the parent to offspring dispersal variance, to be made in plants with a wide variety of sexual systems and with different patterns of vegetative growth.
Abstract: Genetic neighbourhoods in plants with diverse systems of mating and different patterns of growth
TL;DR: Differences in flowering time among clones led to assortative mating between clones which flowered synchronously, and this was accompanied by changes in the genotypic composition of the pollen pool through the flowering season.
Abstract: Pollen success, functional gender and assortative mating in an experimental plant population
TL;DR: It is shown that the method of minimising the perimeter of the polygon obtained by connecting the centromere is only applicable if the positions of the n centromeres do not deviate too much from an arrangement along a regular n-gon.
Abstract: Two aspects of the Bennett model are of interest from a mathematical point of view. First there is the question whether Bennett's "ranking method" for predicting the order of chromosomes will always work. The answer depends on the number n of chromosomes: if n is odd, predictions (being not necessarily unique) are possible in most cases. Secondly there is Bennett's procedure for determining the arrangement of chromosomes. It is shown that the method of minimising the perimeter of the polygon obtained by connecting the centromeres is only applicable if the positions of the n centromeres do not deviate too much from an arrangement along a regular n-gon.
TL;DR: A study of the inheritance of this intra-individual heterogeneity in white clover showed that homogeneity is dominant over heterogeneity and that the heterogeneity of a plant increases with the number of its heterogeneous parents.
Abstract: The pattern of inheritance of the polymorphism of cyanogenesis in white clover, i.e., of two independent loci with a pair of alleles at each locus, is shown to be too simple. Several phenotypes can coexist at the same time in the same plant, without showing any detectable pattern in space or time. A study of the inheritance of this intra-individual heterogeneity showed that homogeneity is dominant over heterogeneity and that the heterogeneity of a plant increases with the number of its heterogeneous parents. The ecological and evolutionary significance of the phenotypic heterogeneity is discussed.
TL;DR: The results suggest that microevolution is retarded in some populations by unfavourable genetic correlation structures among characters under simultaneous selection, by inhomogeneous habitat characteristics or by relatively high levels of phenotypic plasticity.
Abstract: Genetic analysis of ecological relevant morphological variability in Plantago lanceolata L. I Population characteristics 1
TL;DR: It is argued that while the number of heterozygous loci in an individual may not be a good indicator of the individual's genomic heterozygosity, there is evidence that some of the biochemical loci may reflect genetic variation at the loci controlling phenotypic polymorphism.
Abstract: Using the theory of additive genetic variability of a polygenic trait, it is shown that an individual's heterozygosity at the loci governing the trait cannot be determined accurately from observations on phenotypes alone. Furthermore, the negative association between heterozygosity and phenotypic variance, and a positive correlation of the frequency of the modal class of a phenotypic trait and the extent of heterozygosity can be explained by additive allelic effects. It is argued that while the number of heterozygous loci in an individual may not be a good indicator of the individual's genomic heterozygosity, there is evidence that some of the biochemical loci may reflect genetic variation at the loci controlling phenotypic polymorphism. Thus the observed relationship between biochemical heterozygosity and phenotypic variance may not constitute hard evidence of heterosis, overdominance, or associative overdominance.
TL;DR: Populations of the tristylous, self-compatible diploid Eichhornia paniculata (Spreng.) Solms.
Abstract: Populations of the tristylous, self-compatible diploid Eichhornia paniculata (Spreng.) Solms. (Pontederiaceae) display wide variation in floral traits likely to influence the mating system. Progeny tests of open-pollinated plants collected from two populations in N.E. Brazil with contrasting structures (trimorphic, dimorphic) were used to investigate mating patterns. The two loci that govern the inheritance of style length were used as marker genes. A model that measures the magnitude of disassortative mating was developed using the progeny test data. Since the model does not distinguish between selling and assortative mating, outcrossing estimates are likely to be underestimated. Using the model it was shown that the mating patterns of the two populations were strikingly different. In the tristylous population a high level of disassortative mating was estimated (t = 0·903) with no significant differences among the floral morphs. In the dimorphic population (L, M) the rate of disassortative mating of the long-styled morph was t = 0·657, whereas all matings in the mid-styled morph were either selfed or assortative. Selfing in the mid-styled morph is due to alteration of the position of short-level stamens resulting in automatic self-pollination. The consequence of this mating asymmetry on the dynamics of selection at loci controlling floral trimorphism is discussed.
TL;DR: Variation in sequence abundance between strains of A. albopictus was as great as between it and the other six species and copy numbers of highly repeated sequences do not correlate with genome size.
Abstract: Interspecific variation in abundance of highly repeated DNA sequences has been examined in three species of the Aedes scutellaris and three species of the A. albopictus subgroup of the A. scutellaris group. Sequences from a population of A. albopictus were hybridised with whole genomic content from other species and strains. Copy number estimates were determined by dot-blot hybridisation. Variation in sequence abundance between strains of A. albopictus was as great as between it and the other six species. Two clusters were formed by principal components analysis, each of which contains populations of A. albopictus. Copy numbers of highly repeated sequences do not correlate with genome size. The results indicate extensive sequence divergence and rapid evolution. These findings are discussed in relation to the importance of concerted evolution and natural selection in the evolution of the species group.
TL;DR: The results indicate that drift and/or differences in genetic background can lead to divergence under uniform selection, even when fairly large population sizes are maintained.
Abstract: Replicate D. pseudoobscura lines from populations collected at different geographic locations were selected for increased knockdown resistance to ethanol. Population background affected the initial rate of response but not the extent that lines responded. Lines were tested for physiological traits contributing to increased knockdown resistance. Populations showed different correlated responses for two traits (tolerance of ethanol, and of acetone), suggesting that they had responded to selection by different mechanisms. Replicate lines had diverged for most traits. The results indicate that drift and/or differences in genetic background can lead to divergence under uniform selection, even when fairly large population sizes are maintained.
TL;DR: Clonal diversity of obligately parthenogenetic Daphnia pulex was examined in 147 ponds at 13 sites near Churchill, Manitoba, with significant spatial autocorrelation of the distribution of certain clones within a given site on a scale of tens of metres.
Abstract: Clonal diversity of obligately parthenogenetic Daphnia pulex was examined in 147 ponds at 13 sites near Churchill, Manitoba. Cellulose acetate electrophoresis of four polymorphic loci allowed the detection of 16, multi-locus genotypes (clones). The three most common clones accounted for 86 per cent of the 3291 animals surveyed. An average of 1·5 clones coexisted in single ponds, while an average of 3·8 clones was present at each site. Fifteen of the sixteen clones show unbalanced electromorph phenotypes at one or more loci suggesting that they are polyploids. There was significant spatial autocorrelation of the distribution of certain clones within a given site on a scale of tens of metres. Clinal patterns in clone distributions were often found. No significant between-site spatial autocorrelation was found on a scale of 0–20 kilometres, although between-site heterogeneity of clonal frequencies was frequently seen. Microgeographic heterogeneity of D. pulex clones at Churchill is influenced by salinity gradients on a scale of tens of meters. Mechanisms that might influence the clonal structure of this apomictic complex are discussed.
TL;DR: The inheritance of chlorpyrifos resistance has been studied in a strain (MSE) derived from larvae collected in southern France in 1979, using two susceptible strains (S-LAB and YPL) and all F1 offspring displayed straight dosage-mortality lines confirming that the susceptible and the resistant strains were homozygous for the genes involved.
Abstract: Inheritance of chlorpyrifos resistance in Culex pipiens L. (diptera: culicidae) and estimation of the number of genes involved
TL;DR: It is concluded that the choice of base populations between F2 and first backcrosses can be made on the distributions of testcrosses from the first segregating generation, and Schnell's (1983) “usefulness” criterion is recommended for choosing the optimum type of base population.
Abstract: Expectation of means and variances of testcrosses produced from from F 2 and backcross individuals and their selfed progenies
TL;DR: Isolated populations of L. saxatilis indicate that founder events need not lead to drastic genetic alterations, and enable such populations to expand rapidly in a formerly empty habitat.
Abstract: The intertidal snail, L. saxatilis lacks a pelagic stage and migration between populations inhabiting different islands is rare. Small skerries, which are very young habitats, due to the proceeding post-glacial elevation of land, are likely to have been populated by small groups of snails. Mayr's “founder principle” predicts a “genetic revolution” in populations established in this way. Allozyme data, however, reveal but a slight decrease in the level of heterozygosity within these skerry populations, as compared to those of islands and mainland. A probable explanation for this is that although the founding group may consist of only one fertilised female, sperm storage, year-round reproduction, and density-dependent selection enable such populations to expand rapidly in a formerly empty habitat. As has been shown by Nei and coworkers, this will largely impede the loss of genetic variation during the founder event. Isolated populations of L. saxatilis indicate that founder events need not lead to drastic genetic alterations.
TL;DR: The results fail to show a consistent correlation between ethanol tolerance and ADH activity in the adults of LR lines, but indicate that adaptation of D. melanogaster to ethanol-containing food could be accomplished without significant changes on the ADHactivity in the adult flies.
Abstract: The suggestion of Oakeshott et al. (1984) that selection at the Adh locus, as a response to ethanol, is restricted to D. melanogaster laboratory-adapted populations, is tested in this paper with the "Lagar de los Reyes" (LR) lines. For this purpose, homozygous lines for the AdhF and the AdhS alleles were maintained on food supplemented with ethanol. After the selection, the ethanol tolerance and the ADH activity of the selected flies (LRSeF and LRSeS) were determined and compared with those of the control flies (LRCF and LRCS), maintained on standard medium. Then, the effects of the selection, genotype and sex, and the relation between ethanol tolerance and ADH activity were analysed. Our results fail to show a consistent correlation between ethanol tolerance and ADH activity in the adults of LR lines. Our findings also indicate that adaptation of D. melanogaster to ethanol-containing food could be accomplished without significant changes on the ADH activity in the adults. The possibility that the adaptation of D. melanogaster to environmental ethanol could be independent of the Adh locus is discussed.
TL;DR: Comparison of percentage egg hatch, the percentage of first instar larvae reaching adulthood and the time of development from egg to adult for combinations of modifier and resistance genotypes show that the modifier affects only the latter.
Abstract: Modification of the fitness of diazinon resistance genotypes of the Australian sheep blowfly, Lucilia cuprina, in the absence of the insecticide from SS > RS > RR to SS = RS = RR (McKenzie et al., 1982) has been shown previously to be due to the segregation of a gene(s) on chromosome III (McKenzie and Purvis, 1984). In this study the gene (gene complex) is mapped to the w locus region of that chromosome by comparing changes in frequency of SS individuals in population cages initiated with RS genotypes segregating for field derived regions of chromosome III. Comparison of percentage egg hatch, the percentage of first instar larvae reaching adulthood and the time of development from egg to adult for combinations of modifier and resistance genotypes show that the modifier affects only the latter. Developmental time is decreased for RS and RR genotypes. The effect is dominant. The developmental time of SS genotypes is unaffected by modifier genotype.