Mating patterns in self-compatible distylous populations of Amsinckia (Boraginaceae)

1975 ◽  
Vol 53 (8) ◽  
pp. 773-779 ◽  
Author(s):  
Fred R. Ganders
Keyword(s):  
Random Mating ◽  
Marker Gene ◽  
Natural Populations ◽  
Breeding Systems ◽  
High Rate ◽  
Structure Population ◽  
Disassortative Mating ◽  
Progeny Tests ◽  
Flower Form ◽  
Two Populations

Progeny tests of naturally pollinated pin- and thrum-form plants of two species of Amsinckia were conducted to determine whether net selfing, random mating, or net disassortative mating occurred in natural populations. The locus determining flower form was used as a marker gene. Amsinckia spectabilis experienced close to random mating in a dense population, but in a small, diffuse population a high rate of selfing was indicated. Pin plants of Amsinckia vernicosa var. furcata experienced 44.3% net disassortative mating, and thrum plants in this species experienced complete (100%) disassortative mating.Compared with A. spectabilis, stigmas and anthers are about twice as far apart in A. vernicosa var. furcata; yet the pollinators are essentially similar, suggesting that greater separation of stigmas and anthers greatly improves the efficiency of distyly at promoting disassortative pollination. The two populations of A. spectabilis studied indicate that autogamy and (or) geitonogamy is much higher in diffuse populations. The results support previous studies that disassortative pollination is greater in thrum-form flowers than in pin flowers. Distyly without self-incompatibility can be an effective outbreeding system but is much more sensitive to variations in floral structure, population density, and pollinator behavior than are self-incompatible breeding systems.

Cone serotiny and inbreeding in natural populations of Pinus banksiana and Pinus contorta

1970 ◽  
Vol 48 (10) ◽  
pp. 1805-1809 ◽  
Author(s):  
A. H. Teich
Keyword(s):  
Pinus Banksiana ◽  
Pinus Contorta ◽  
Environmental Influence ◽  
Single Gene ◽  
Marker Gene ◽  
Natural Populations ◽  
Inbreeding Coefficient ◽  
Gene Frequencies ◽  
Progeny Tests ◽  
Individual Trees

Cone serotiny in jack and lodgepole pine was studied by applying the Hardy–Weinberg law to data from several populations, and by examining data on progeny of individual trees. Cone serotiny appears to be governed by a single gene with two alleles. The phenotype of the heterozygote is intermediate to that of both homozygotes and is subject to environmental influence. Because of this a proportion of the heterozygotes may have been misidentified as homozygotes, which inflated the inbreeding coefficient, making it unreliable. Progeny tests or other means of correctly identifying heterozygotes would allow the use of cone serotiny as a marker gene for hybridization and relate populations by their similarity of gene frequencies.

scholarly journals On the Rate and Linearity of Viability Declines in Drosophila Mutation-Accumulation Experiments: Genomic Mutation Rates and Synergistic Epistasis Revisited

Genetics ◽  
2004 ◽  
Vol 166 (2) ◽  
pp. 797-806 ◽  
Author(s):  
James D Fry
Keyword(s):  
Mutation Rate ◽  
Average Rate ◽  
Natural Populations ◽  
Mutation Accumulation ◽  
High Rate ◽  
Deleterious Mutations ◽  
Order Of Magnitude ◽  
Contamination Event ◽  
Genomic Mutation ◽  
The 1960S

Abstract High rates of deleterious mutations could severely reduce the fitness of populations, even endangering their persistence; these effects would be mitigated if mutations synergize each others’ effects. An experiment by Mukai in the 1960s gave evidence that in Drosophila melanogaster, viability-depressing mutations occur at the surprisingly high rate of around one per zygote and that the mutations interact synergistically. A later experiment by Ohnishi seemed to support the high mutation rate, but gave no evidence for synergistic epistasis. Both of these studies, however, were flawed by the lack of suitable controls for assessing viability declines of the mutation-accumulation (MA) lines. By comparing homozygous viability of the MA lines to simultaneously estimated heterozygous viability and using estimates of the dominance of mutations in the experiments, I estimate the viability declines relative to an appropriate control. This approach yields two unexpected conclusions. First, in Ohnishi’s experiment as well as in Mukai’s, MA lines showed faster-than-linear declines in viability, indicative of synergistic epistasis. Second, while Mukai’s estimate of the genomic mutation rate is supported, that from Ohnishi’s experiment is an order of magnitude lower. The different results of the experiments most likely resulted from differences in the starting genotypes; even within Mukai’s experiment, a subset of MA lines, which I argue probably resulted from a contamination event, showed much slower viability declines than did the majority of lines. Because different genotypes may show very different mutational behavior, only studies using many founding genotypes can determine the average rate and distribution of effects of mutations relevant to natural populations.

scholarly journals Inferring Linkage Disequilibrium Between a Polymorphic Marker Locus and a Trait Locus in Natural Populations

Genetics ◽  
2000 ◽  
Vol 156 (1) ◽  
pp. 457-467 ◽  
Author(s):  
Z W Luo ◽  
S H Tao ◽  
Z-B Zeng
Keyword(s):  
Linkage Disequilibrium ◽  
Allele Frequency ◽  
Random Mating ◽  
Natural Populations ◽  
Polymorphic Marker ◽  
Marker Locus ◽  
Model Parameters ◽  
Phenotypic Variance ◽  
Wide Range ◽  
Trait Locus

Abstract Three approaches are proposed in this study for detecting or estimating linkage disequilibrium between a polymorphic marker locus and a locus affecting quantitative genetic variation using the sample from random mating populations. It is shown that the disequilibrium over a wide range of circumstances may be detected with a power of 80% by using phenotypic records and marker genotypes of a few hundred individuals. Comparison of ANOVA and regression methods in this article to the transmission disequilibrium test (TDT) shows that, given the genetic variance explained by the trait locus, the power of TDT depends on the trait allele frequency, whereas the power of ANOVA and regression analyses is relatively independent from the allelic frequency. The TDT method is more powerful when the trait allele frequency is low, but much less powerful when it is high. The likelihood analysis provides reliable estimation of the model parameters when the QTL variance is at least 10% of the phenotypic variance and the sample size of a few hundred is used. Potential use of these estimates in mapping the trait locus is also discussed.

The Kota of the Nilgiri hills: a demographic study

1976 ◽  
Vol 8 (1) ◽  
pp. 17-26 ◽  
Author(s):  
Aloke Kumar Ghosh
Keyword(s):  
Total Population ◽  
Random Mating ◽  
High Rate ◽  
Moderate Intensity ◽  
Biological Study ◽  
Isolated Population ◽  
Demographic Structure ◽  
Effective Population ◽  
Mating Population ◽  
The Village

A population–biological study of the Kota of the Nilgiri Hills was undertaken between May 1966 and January 1968. This paper discusses the demographic structure of the tribe and its genetic implications.The Kota is a small tribe of 1203 individuals distributed in only seven villages; it is an isolated population with a low rate of fertility and a high rate of infant mortality. The Kota is not a random mating population. The rate of consanguineous marriages is high and the coefficient of inbreeding is almost equal to the highest recorded value. Besides cousin marriages, marriage within the village is very much preferred. The admixture rate (0·29%) among the Kota is very low. The effective population size is only 28·87% of the total population. The coefficient of breeding isolation is 1·01, which indicates that genetic drift may produce important differentiation in this population. The data show that selection is acting with moderate intensity in this population.

scholarly journals Locating the Sex Determining Region of Linkage Group 12 of Guppy (Poecilia reticulata)

2020 ◽  
Vol 10 (10) ◽  
pp. 3639-3649
Author(s):  
Deborah Charlesworth ◽  
Roberta Bergero ◽  
Chay Graham ◽  
Jim Gardner ◽  
Lengxob Yong
Keyword(s):  
Poecilia Reticulata ◽  
Population Genomics ◽  
False Positive Rate ◽  
Natural Populations ◽  
Proximal Region ◽  
High Rate ◽  
Chromosome 12 ◽  
Small Samples ◽  
Autosomal Region ◽  
Y Chromosomes

Despite over 100 years of study, the location of the fully sex-linked region of the guppy (Poecilia reticulata) carrying the male-determining locus, and the regions where the XY pair recombine, remain unclear. Previous population genomics studies to determine these regions used small samples from recently bottlenecked captive populations, which increase the false positive rate of associations between individuals’ sexes and SNPs. Using new data from multiple natural populations, we show that a recently proposed candidate for this species’ male-determining gene is probably not completely sex-linked, leaving the maleness factor still unidentified. Variants in the chromosome 12 region carrying the candidate gene sometimes show linkage disequilibrium with the sex-determining factor, but no consistently male-specific variant has yet been found. Our genetic mapping with molecular markers spread across chromosome 12 confirms that this is the guppy XY pair. We describe two families with recombinants between the X and Y chromosomes, which confirm that the male-determining locus is in the region identified by all previous studies, near the terminal pseudo-autosomal region (PAR), which crosses over at a very high rate in males. We correct the PAR marker order, and assign two unplaced scaffolds to the PAR. We also detect a duplication, with one copy in the male-determining region, explaining signals of sex linkage in a more proximal region.

scholarly journals Kin-Mediated Male Choice and Alternative Reproductive Tactics in Spider Mites

Biology ◽  
2020 ◽  
Vol 9 (11) ◽  
pp. 360
Author(s):  
Peter Schausberger ◽  
Yukie Sato
Keyword(s):  
Random Mating ◽  
Reproductive Potential ◽  
Spider Mites ◽  
Alternative Reproductive Tactics ◽  
Male Choice ◽  
Reproductive Tactics ◽  
Kin Competition ◽  
Context Specific ◽  
Two Populations

Optimal outbreeding and kin selection theories state that the degree of kinship is a fundamental determinant in any mating system. However, the role of kinship in male choice and alternative reproductive tactics (ARTs) is poorly known. We assessed the influence of kinship on male choice and expression of ARTs in two populations of two-spotted spider mites Tetranychus urticae. Male spider mites guard premature females, which is an indicator of mate choice, and may conditionally adopt fighting or sneaking tactics to secure access to females. Males competing with kin or non-kin were offered one kin or non-kin female (experiment 1) and single males were presented a choice of kin and non-kin females (experiment 2). Under kin competition, males of both populations were more prone to guard non-kin than kin females at a 3:1 fighter:sneaker ratio. Under non-kin competition, all males were fighters. Under no-choice, males used novelty as indicator of genetic dissimilarity, serving as absolute decision rule for outbreeding. Under choice, comparative evaluation allowed males to preferentially guard females with higher reproductive potential. Overall, our study suggests that male spider mites can assess kinship of rivals and prospective mates. Kin discrimination allows adaptive, context-specific non-random mating preference and adjustment of ARTs.

scholarly journals The health of laboratory mice A comparison of general health in two breeding units where different systems are employed

1959 ◽  
Vol 57 (4) ◽  
pp. 386-402 ◽  
Author(s):  
A. A. Tuffery
Keyword(s):  
Breeding System ◽  
General Health ◽  
Post Partum ◽  
High Standard ◽  
Point Of View ◽  
Breeding Systems ◽  
Pregnant Females ◽  
Serious Infections ◽  
Sporadic Cases ◽  
Two Populations

Two units, within a mouse-breeding colony, with different breeding systems, have been compared from the point of view of general healthiness of the breeding stock. In one unit the monogamous-pair system, involving post-partum oestrus mating, was employed and in the other the harem system, with isolation of the pregnant females for each litter-down until after the post-partum oestrus. The two units were housed separately and had different staffs. The monogamous-pair unit was accommodated in four small rooms not directly connected; the harem unit in two larger connecting rooms. The methods of cageing, bedding, feeding, watering, care, culling and subsequent procedures were identical for both units and the same system of recording individual detailed information relating to health and breeding was followed for the two units. The size of the two populations studied was 1198 and 1024, respectively, the larger number belonging to the harem unit in which the mice were retained for a significantly longer period. These mice were moved more frequently and handled much more often.Apart from a small outbreak of Tyzzer's disease (in the harem-bred unit) and sporadic cases in both units spread over the whole period of the survey—some 3–4 years—the general health of the two units was good. There were no cases of salmonella infection, mousepox, pasteurellosis or other serious infections. Throughout the period both units maintained a high standard of productivity and there was no evidence that the mating of the monogamous pairs at the post-partum oestrus led to any weakness or ill health. As would be expected, however, the losses from death and culling were greater among the females in both units.The health record of the monogamous-pair bred unit was consistently higher than that of the harem-bred unit. There were more cases of Tyzzer's disease in the harem-bred mice and more evidence generally of ill health in this unit. Infertility was three times greater with the harem-bred mice as compared with those in the monogamous-pair unit.Details of the two systems are discussed and although the records maintained for the two may not be strictly comparable it is concluded that, under the conditions obtaining, the monogamous-pair breeding system yielded a healthier colony of mice than the harem breeding system.I should like to thank Dr J. S. Patterson and Mr R. Cook for placing many of their records at my disposal, Mr S. Peto and his staff for carrying out much of the tedious compilation of data, and Dr D. W. Henderson, F.R.S., for affording me facilities for this work. To these I am especially grateful for their interest, advice and assistance.

scholarly journals Population frequencies of transposable elements in selfing and outcrossingCaenorhabditisnematodes

2008 ◽  
Vol 90 (4) ◽  
pp. 317-329 ◽  
Author(s):  
ELIE S. DOLGIN ◽  
BRIAN CHARLESWORTH ◽  
ASHER D. CUTTER
Keyword(s):  
Transposable Elements ◽  
Genome Sequence ◽  
Natural Populations ◽  
Purifying Selection ◽  
Breeding Systems ◽  
Inverted Repeats ◽  
Insertion Polymorphism ◽  
C Elegans ◽  
Selfish Genetic Elements ◽  
Caenorhabditis Remanei

SummaryPopulation genetics theory predicts that differences in breeding systems should be an important factor in the dynamics of selfish genetic elements, because of different intensities of selection on both hosts and elements. We examined population frequencies of transposable elements (TEs) in natural populations of the self-fertilizing nematodeCaenorhabditis elegansand its outcrossing relativeCaenorhabditis remanei. We identified a Tc1-like class of elements in theC. remaneigenome with homology to the terminal inverted repeats of theC. elegansTc1 transposon, which we name mTcre1. We measured levels of insertion polymorphism for all 32 Tc1 elements present in the genome sequence of theC. elegansN2 strain, and 16 mTcre1 elements from the genome sequence of theC. remaneiPB4641 strain. We show that transposons are less polymorphic and segregate at higher frequencies inC. eleganscompared withC. remanei. Estimates of the intensity of selection based on the population frequencies of polymorphic elements suggest that transposons are selectively neutral inC. elegans, but subject to purifying selection inC. remanei. These results are consistent with a reduced efficacy of natural selection against TEs in selfing populations, but may in part be explained by non-equilibrium TE dynamics.

Variation in cone morphology and seed characters in Pinus strobus in Quebec

1995 ◽  
Vol 73 (2) ◽  
pp. 262-271 ◽  
Author(s):  
Jean Beaulieu ◽  
Jean-Pierre Simon
Keyword(s):  
Natural Populations ◽  
Pinus Strobus ◽  
White Pine ◽  
Ottawa River ◽  
River Region ◽  
Natural Range ◽  
Anticosti Island ◽  
Genotypic Control ◽  
Two Populations ◽  
Cone Scale

To investigate the patterns of variation in white pine (Pinus strobus L.), 10 natural populations from Quebec were compared using the phenotypic variation of cone and seed traits. Eight characters were measured on 10 cones collected from 30 trees in each of the 10 sampled populations. Four populations were from the Ottawa River region and four from the St. Lawrence Lowlands region, while two populations were at the margin of the natural range of the species in Quebec, from the Abitibi region and Anticosti Island. Significant differences among populations were detected for each character. Estimates of repeatability of these traits were relatively high, suggesting substantial genotypic control over them. These estimates were consistent from population to population. Results of multivariate analyses suggest that populations from the Ottawa River region are similar to those from the St. Lawrence region, with populations from these regions diverging only in cone scale length. However, populations from the St. Lawrence region were more distinct from each other than those from the Ottawa River region. The population from Abitibi deviates considerably from the other populations, suggesting habitat-selection pressures acting at the margin of the natural range of the species under continental conditions. Finally, no general geographical trend was detected in the observed variation. Key words: white pine, morphology, cone, seed, variation.

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