Colonization of the Americas by Drosophila subobscura: lethal-gene allelism and association with chromosomal arrangements.

Abstract Drosophila subobscura is a Palearctic species that has recently colonized the Americas. It was first found in 1978 in Puerto Montt, Chile, and in 1982 in Port Townsend, WA. The colonization and rapid expansion of the species in western South and North America provides distinctive opportunities for investigating the process of evolution in action. The inversion polymorphism in the O chromosome from populations of central California and northern Washington, separated by 1300 km, corresponds to a previously observed latitudinal cline, also observed in Europe. Recessive lethal genes are not randomly distributed among the chromosomal arrangements. The incidence of lethal allelism is high, yielding unrealistically low estimates of the effective size of these populations (on the order of 1000 individuals). The high incidence of lethal allelism is likely to be a consequence of the low number of the American colonizers (on the order of 10-100 individuals), but the persistence of the allelism over several years suggests that some lethal-carrying chromosomes may be heterotic owing to shared associations between lethal and other genes.

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Biosystematic studies in the Stylidium crassifolium species complex (Stylidiaceae)

Australian Journal of Botany ◽

10.1071/bt9790027 ◽

1979 ◽

Vol 27 (1) ◽

pp. 27 ◽

Cited By ~ 19

Author(s):

BJ Banyard ◽

SH James

Keyword(s):

Species Complex ◽

Genetic System ◽

Lethal Gene ◽

Great Efficiency ◽

Intermediate Species ◽

Gene Arrays ◽

Recessive Lethal ◽

Tetraploid Form ◽

Diploid Populations ◽

Lethal Genes

Stylidium elongatum Benth. (n = 13, 26) and Stylidium crassifolium R. Br. (n = 14, 28) have been restored to specific status and a morphologically intermediate species, Stylidium confluens sp. nov. (n = 14), is described. Polyploid entities in the complex have not been given taxonomic ranks although the tetraploid form of elongatum may be considered worthy of subspecific rank, as it is ecologically distinct and contiguously allopatric to its progenitor and to confluens, forming a buffer between these two diploid entities. Tetraploid populations in crassifolium occur within the distributional range of the diploid. All three species carry recessive lethal gene arrays which eliminate the products of self-pollination with great efficiency and result in crosses between close populations yielding seed more effectively than crosses within populations. There is evidence that interpopulational coadaptation may break down with increasing distance between populations. Polyploidy in crassifolium is probably a conservative response in the genetic system of a species where concentrations of lethal genes in small diploid populations became disadvantageous.

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A grand experiment in evolution: the Drosophila subobscura colonization of the Americas

Genome ◽

10.1139/g89-042 ◽

1989 ◽

Vol 31 (1) ◽

pp. 246-255 ◽

Cited By ~ 74

Author(s):

Francisco J. Ayala ◽

Luis Serra ◽

Antonio Prevosti

Keyword(s):

Mitochondrial Dna ◽

Sierra Nevada ◽

Strong Evidence ◽

Polytene Chromosomes ◽

Western Mediterranean ◽

Drosophila Subobscura ◽

Lethal Gene ◽

Allozyme Polymorphism ◽

Old World ◽

Lethal Allelism

Drosophila subobscura is a Palearctic species that has been extensively studied by population and evolutionary geneticists for nearly half a century. In 1978, it appeared in Puerto Montt, Chile; within a few years it extended over much of Chile and into Argentina and became the most common drosophilid in many places. In 1982, it appeared in the American northwest; shortly thereafter it was found extensively distributed from southern British Columbia, through Washington and Oregon, into southern California, west of Sierra Nevada. In North America also it has become a common drosophilid in many places. The source of the colonizers has been sought with four lines of research: sequence arrangement of the polytene chromosomes, allozyme polymorphisms, mitochondrial DNA restriction patterns, and frequency of lethal alleles. The origin of the colonizers remains uncertain, although all evidence indicates that both the North American and the South American colonizers derive from the same Palearctic population. The overall configuration of the chromosomal and allozyme frequencies suggests a western Mediterranean origin, which is consistent with the mtDNA data. The presence of a particular chromosome arrangement, O5, suggests a northern European origin. Lethal allelism has opened up the possibility of discovering the precise origin of the colonizers: all O5 chromosomes in the Americas carry a particular recessive lethal gene. There is strong evidence that the number of founders was not very small and not very large, perhaps between 10 individuals and several score. The chromosomal polymorphisms of D. subobscura exhibit well-defined latitudinal clines in the Old World. In the few years since the colonization, clines in every chromosome have evolved in the Americas that have identical latitudinal polarity with those in the Old World. This would seem strong evidence that the polymorphisms and the clines are adaptive.Key words: chromosomal polymorphism, mitochondrial DNA evolution, allozyme polymorphism, lethal allelism, adaptation, geographic clines.

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Why Recessive Lethal Alleles Have Not Disappeared?

Annual Research & Review in Biology ◽

10.9734/arrb/2021/v36i630391 ◽

2021 ◽

pp. 69-80

Author(s):

Jorma Jormakka ◽

Sourangshu Ghosh

Keyword(s):

Ethnic Groups ◽

Lethal Gene ◽

Recessive Lethal ◽

Lethal Genes

The article derives the probability for lethal recessive alleles in the case of recessive disadvantage or advantage. It is shown that recessive advantage of a lethal gene can be detected by the ratio of heterozygotes and homozygotes. This demonstrates that higher IQ of certain ethnic groups cannot be explained by recessive advantage of lethal genes. The article shows that lethal genes can survive in the population if some lineages of families have much more children than the average.

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Why Recessive Lethal Alleles Have Not Disappeared?

10.20944/preprints202105.0751.v1 ◽

2021 ◽

Author(s):

Jorma Jormakka ◽

Sourangshu Ghosh

Keyword(s):

Ethnic Groups ◽

Lethal Gene ◽

Recessive Lethal ◽

Lethal Genes

The article derives the probability for lethal recessive alleles in the case of recessive disadvantage or advantage. It is shown that the recessive advantage of a lethal gene can be detected by the ratio of heterozygotes and homozygotes. This demonstrates that the higher IQ of certain ethnic groups cannot be explained by the recessive advantage of lethal genes. The article shows that lethal genes can survive in the population if some lineages of families have much more children than the average.

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The role of the genome in the development of the haploid syndrome in Anura

Development ◽

10.1242/dev.16.3.559 ◽

1966 ◽

Vol 16 (3) ◽

pp. 559-568

Author(s):

Louie Hamilton

Keyword(s):

Good Evidence ◽

Contributory Factor ◽

Diploid Nucleus ◽

Haploid Nucleus ◽

Recessive Lethal ◽

Partial Failure ◽

Lethal Genes

The problem of the factors involved in the development of the haploid syndrome in anuran embryos is as yet unsolved. It is known that about 90 % of all haploid frog embryos develop the haploid syndrome, which is characterized by the presence of oedema and sluggishness, by reduction in pigmentation and in the efficiency of the heart and circulation, and by a partial failure of the gut to coil and of muscle to differentiate. The two most favoured explanations of the development of the haploid syndrome have been nucleocytoplasmic imbalance, since a haploid nucleus is only half the size of a diploid nucleus in the same-sized egg, and unmasked recessive lethal genes. There is good evidence that an abnormal nucleocytoplasmic ratio is an important contributory factor in the development of the haploid syndrome. Briggs (1949) compared populations of haploids developing from large and small eggs and Subtelny (1958) compared the development of haploids and homozygous diploids which possessed a reduplicated set of haploid chromosomes.

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