GENETICS OF NATURAL POPULATIONS. XIX. ORIGIN OF HETEROSIS THROUGH NATURAL SELECTION IN POPULATIONS OF DROSOPHILA PSEUDOOBSCURA

GENETICS OF NATURAL POPULATIONS. XIX. ORIGIN OF HETEROSIS THROUGH NATURAL SELECTION IN POPULATIONS OF DROSOPHILA PSEUDOOBSCURA Theodosius Dobzhansky

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GENETICS OF NATURAL POPULATIONS. XIX. ORIGIN OF HETEROSIS THROUGH NATURAL SELECTION IN POPULATIONS OF DROSOPHILA PSEUDOOBSCURA 1950 Genetics 10.1093/genetics/35.3.288 dobzhansky1950-genetics-of-natural-populations-xi dobzhansky1950-genetics-of-natural-populations-xi.txt, the project's staged copy 35751fcbd3ca05da51bd9fb4158590c8810961e6 open-access population-genetics

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0 spans located by searching the stored text for the quote's exact words, allowing any whitespace between them mechanism Quotation withheld because this record is not cleared for redistribution. heterosis in chromosomal inversion heterozygotes Quotation withheld because this record is not cleared for redistribution. experiment experiment Quotation withheld because this record is not cleared for redistribution. mechanisms Natural selection coadapts polygene complexes only within a population, so chromosomes brought together from populations that never interbreed have not been mutually adjusted and their heterozygotes lack heterosis. Quotation withheld because this record is not cleared for redistribution. mechanisms Heterosis arises from interaction between polygene complexes carried by differently arranged chromosomes, which the inversions protect from being broken up by crossing over in the heterozygote. Quotation withheld because this record is not cleared for redistribution. mechanisms A second, distinct kind of heterosis arises when deleterious recessive mutants accumulated in the population are sheltered by their normal dominant alleles in the heterozygote. Quotation withheld because this record is not cleared for redistribution. mechanisms Viability and adaptive value diverge because larval survival is only one of several components (adult longevity, fecundity, sexual activity) that jointly determine net fitness. Quotation withheld because this record is not cleared for redistribution. The cages were not run long enough for the inferior chromosome type to be eliminated, so the predicted outcome was not observed to completion. what this limits: the elimination prediction specifically: THE CH CHROMOSOMES WERE RARE IN CAGES NOS. 48 AND 49, BUT MUCH LONGER OBSERVATION WOULD BE NEEDED TO SEE THEM ELIMINATED COMPLETELY Quotation withheld because this record is not cleared for redistribution. In the California-Mexico cage No. 55 the viability differences among genotypes did not reach conventional significance. what this limits: the viability comparison in cage No. 55: THE DIFFERENCES ARE, HOWEVER, MOSTLY BELOW THE CONVENTIONAL LEVEL OF STATISTICAL SIGNIFICANCE Quotation withheld because this record is not cleared for redistribution. The paper opens its discussion by saying the term names several scarcely related phenomena that the field treats as one. what this limits: any result reported as heterosis or hybrid vigor: the paper states these terms Quotation withheld, so two such results need not be about the same thing Quotation withheld because this record is not cleared for redistribution. Fitness measured at one developmental stage can point the opposite way from fitness overall, and the paper gives its own case. what this limits: a fitness or survival figure from a single developmental stage: adaptive value is stated not to be proportional to survival value at all stages, and here some types with higher egg-to-adult mortality were nevertheless adaptively superior Quotation withheld because this record is not cleared for redistribution. The effect is a property of chromosomes that evolved together, so the same gene-arrangement label does not carry the same behaviour between localities. what this limits: a heterosis result carried from one population to another: polygene complexes from geographically distant localities have not undergone coadaptation, so the same chromosomal type does not behave the same way in a different population Quotation withheld because this record is not cleared for redistribution. inversion heterozygotes compared against inversion homozygotes, with the paper noting that the heterozygotes were also heterozygous for geographical gene complexes eliminates: very little on its own - and the paper says so, which is why this is worth recording: it names the confound its own comparison does not remove · outcome (stated by the tagger, no quotation): partial Quotation withheld because this record is not cleared for redistribution. heterosis heterosis Quotation withheld because this record is not cleared for redistribution. euheterosis euheterosis Quotation withheld because this record is not cleared for redistribution. luxuriance luxuriance Quotation withheld because this record is not cleared for redistribution. adaptive value adaptive value Quotation withheld because this record is not cleared for redistribution. polygene complexes polygene complexes Quotation withheld because this record is not cleared for redistribution. population cages population cages Quotation withheld because this record is not cleared for redistribution. heterosis - KIND ONE, AN ACCIDENT OF MUTATION: superiority arising because deleterious recessive mutants are hidden by their dominant alleles, which is a by-product of the mutation process Quotation withheld because this record is not cleared for redistribution. heterosis - KIND TWO, A PRODUCT OF SELECTION: specific interaction effects from complexes of linked polygenes, called overdominance, engendered by natural selection as adaptation Quotation withheld because this record is not cleared for redistribution. adaptive value - AS FREQUENCY CHANGE IN A CAGE: not a physiological measurement but the observed change in the relative frequencies of two types over time in a population cage Quotation withheld because this record is not cleared for redistribution. builds-on → Wright and Dobzhansky (1946) and Dobzhansky (1947a, b) population-cage results on within-population heterosis Quotation withheld because this record is not cleared for redistribution. polygene complexes —causes→ heterosis polygene complexes heterosis strength of the relation: 1 Quotation withheld because this record is not cleared for redistribution. euheterosis —distinct-from→ luxuriance euheterosis luxuriance strength of the relation: 1 Quotation withheld because this record is not cleared for redistribution. EVIDENCE CORRECTED (RE-GROUNDED) · adaptive value —operationalised-as→ population cages adaptive value population cages EVIDENCE CORRECTED: RE-GROUNDED. Same sentence, CARRIED TO ITS END. The old span stopped at 'observing the…' and lost the apparatus; the full sentence finishes '…breeding in POPULATION CAGES…', which is the operationalisation the edge records. The broken word 'popula tions' is the staged text's own and is quoted as it stands. — strength of the relation: 1 Audit 2026-09-28: DOUBTFUL - read against its full span and kept, but adaptive values are DETERMINED by observing frequencies in population cages; operationalised-as is loose. Quotation withheld because this record is not cleared for redistribution. chi-squared chi-squared Quotation withheld because this record is not cleared for redistribution. degrees of freedom degrees of freedom Quotation withheld because this record is not cleared for redistribution. significance level significance level Quotation withheld because this record is not cleared for redistribution. Inversion heterozygotes built from two third chromosomes of the same population show heterosis, but heterozygotes built from chromosomes of geographically remote populations generally do not. Quotation withheld because this record is not cleared for redistribution. In every experiment one homozygote was sharply less viable than the heterozygote (quotients 0.17 to 0.76). Quotation withheld because this record is not cleared for redistribution. Heterozygosity for same-population ST and AR third chromosomes raises viability even on a geographically mixed background of the other chromosomes. Quotation withheld because this record is not cleared for redistribution. In both cages the adaptive values were ST/AR > ST/ST > AR/AR, the reverse of the viability relations in cage 46. Quotation withheld because this record is not cleared for redistribution. By March 1948 Arrowhead had risen to 91 percent and Chiricahua had fallen to 9 percent. Quotation withheld because this record is not cleared for redistribution. In cage 56 the Pinon Arrowhead homozygote was significantly more viable than the heterozygote, and the Mexican Chiricahua homozygote equally or slightly more viable. Quotation withheld because this record is not cleared for redistribution. A type's adaptive value (net fitness) is not necessarily proportional to its survival at every developmental stage. Quotation withheld because this record is not cleared for redistribution. coadaptation coadaptation Quotation withheld because this record is not cleared for redistribution. viability quotient viability quotient Quotation withheld because this record is not cleared for redistribution. 0.17 to 0.76 — Range of viability quotients of the inferior homozygote relative to the heterozygote across the five geographically mixed cages Quotation withheld because this record is not cleared for redistribution. chi-squares 6.63 to 16.05 — Range of chi-squared values testing the inferiority of the poorly viable homozygote against the heterozygote, on the pooled sexes Quotation withheld because this record is not cleared for redistribution. 91 percent ... 9 percent — Frequencies of Mather Arrowhead and Pinon Chiricahua chromosomes in cage 45 by March 1948, from an equal start in February 1947 Quotation withheld because this record is not cleared for redistribution. 79 percent ... 53 percent — Equilibrium frequency of Arrowhead reached in pure Pinon Flats and in pure Mather populations, against which the runaway hybrid cages are compared Quotation withheld because this record is not cleared for redistribution. 1,217 — Number of AR/CH heterozygote flies introduced into population cage No. 45 at the start of the experiment Quotation withheld because this record is not cleared for redistribution. 300 miles — Distance between the two Californian source localities, Mather and Pinon Flats Quotation withheld because this record is not cleared for redistribution. 31:32 — Probability that both chromosomal types of a heterozygous parent are detected when six larvae are examined, implying one thirty-second of heterozygotes are misclassified as homozygotes Quotation withheld because this record is not cleared for redistribution.

The full text of this article is not redistributable, so it is not included here. The evidence sentences are withheld with it; the tag layer and its grounding status remain. The article itself is at https://doi.org/10.1093/genetics/35.3.288.