GENETICS OF NATURAL POPULATIONS. XII. EXPERIMENTAL REPRODUCTION OF SOME OF THE CHANGES CAUSED BY NATURAL SELECTION IN CERTAIN POPULATIONS OF DROSOPHILA PSEUDOOBSCURA

GENETICS OF NATURAL POPULATIONS. XII. EXPERIMENTAL REPRODUCTION OF SOME OF THE CHANGES CAUSED BY NATURAL SELECTION IN CERTAIN POPULATIONS OF DROSOPHILA PSEUDOOBSCURA Sewall Wright Theodosius Dobzhansky

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GENETICS OF NATURAL POPULATIONS. XII. EXPERIMENTAL REPRODUCTION OF SOME OF THE CHANGES CAUSED BY NATURAL SELECTION IN CERTAIN POPULATIONS OF DROSOPHILA PSEUDOOBSCURA 1946 Genetics 10.1093/genetics/31.2.125 wright1946-genetics-of-natural-populations-xi wright1946-genetics-of-natural-populations-xi.txt, the project's staged copy fd5a601c1d9431d7e4742c4c828b558d3fb58235 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. seasonal cycles in chromosomal inversion frequencies Quotation withheld because this record is not cleared for redistribution. experiment experiment Quotation withheld because this record is not cleared for redistribution. mechanisms Heterozygote superiority: because ST/CH heterozygotes are fitter than either homozygote, selection drives the population towards an intermediate equilibrium of chromosome frequencies rather than fixation. Quotation withheld because this record is not cleared for redistribution. mechanisms The inversions themselves are adaptively neutral, but they lock up different gene complexes that adapt their carriers to different seasonal environments, so seasonal change in the environment shifts their frequencies. Quotation withheld because this record is not cleared for redistribution. mechanisms Frequency-dependent selection through niche filling: a rare genotype occupies only the niches it is best adapted to and is favoured, but when abundant it must spill into niches it fits poorly and is selected against. Quotation withheld because this record is not cleared for redistribution. Absence of significant change at the low temperature may reflect too few sampling intervals rather than genuinely constant frequencies. what this limits: the low-temperature null: THIS DOES NOT IMPLY THAT THERE WERE NO CHANGES BUT MERELY THAT ANY CHANGES WERE TOO SMALL TO BE DETECTED WITH CONFIDENCE IN THE SMALL NUMBER OF INTERVALS Quotation withheld because this record is not cleared for redistribution. The data cannot discriminate among the possible selective models (constant selective values, sex-differential selection, frequency-dependent values). what this limits: any choice among the selective models: UNFORTUNATELY THE DATA AT HAND DO NOT YIELD A UNIQUE INTERPRETATION Quotation withheld because this record is not cleared for redistribution. The spring reversal seen in nature was not reproduced and its causes remain unknown. what this limits: the correspondence with the wild population: the spring reversal was not reproduced, and THERE ARE IMPORTANT FACTORS YET TO BE DISCOVERED Quotation withheld because this record is not cleared for redistribution. A counting assumption is made, stated to be false in some strains, and the direction of the resulting error is given: the tabulated numbers are minima. what this limits: the counts of kinds of chromosomes in table 2: they rest on an assumption the authors state is violated in some strains, so the numbers are minima rather than estimates Quotation withheld because this record is not cleared for redistribution. The baseline the experiment is compared against is inferred rather than observed, and the authors offer that as one of two explanations for the unexpected control differences. what this limits: the control samples as showing the initial composition: the authors note the initial population's composition is inferred from its parents, and offer sampling error as the alternative explanation Quotation withheld because this record is not cleared for redistribution. a Control sample whose gene-arrangement frequencies should match the initial population, against which the experimental cages are read eliminates: drift and sampling as the explanation of a frequency change - the Control sample is the one that should show no change, and it is what makes a change elsewhere readable · outcome (stated by the tagger, no quotation): held Quotation withheld because this record is not cleared for redistribution. gene arrangement gene arrangement Quotation withheld because this record is not cleared for redistribution. Standard Standard Quotation withheld because this record is not cleared for redistribution. population cage population cage Quotation withheld because this record is not cleared for redistribution. evidence of selection - a TWO-PART criterion: the average rate of change per generation AND the regression of that rate on chromosome frequency, both of which must be considered Quotation withheld because this record is not cleared for redistribution. evidence of selection - AS A REGRESSION OF RATE ON FREQUENCY, which the paper says indicates selection EVEN IF the average does not differ significantly from zero about this quote: THE QUOTE CONTINUES A SENTENCE THAT THIS COPY CUTS IN TWO - a running head and a stray full stop stand between it and the words it follows, which read 'obviously indicates a selective' and, after the head, 'process,'. Quotation withheld because this record is not cleared for redistribution. initial population composition - not measured but INFERRED from the composition of the parents, while the control sample describes something else Quotation withheld because this record is not cleared for redistribution. builds-on → L'Heritier and Teissier's population cage Quotation withheld because this record is not cleared for redistribution. contradicts → Hovanitz (1944) migration explanation of the seasonal changes at Pinon Flats and Andreas Canyon Quotation withheld because this record is not cleared for redistribution. Standard —is-a→ gene arrangement Standard gene arrangement strength of the relation: 1 Quotation withheld because this record is not cleared for redistribution. chi-squared chi-squared Quotation withheld because this record is not cleared for redistribution. t-test (Student's) t-test (Student's) Quotation withheld because this record is not cleared for redistribution. regression regression Quotation withheld because this record is not cleared for redistribution. F-test F-test Quotation withheld because this record is not cleared for redistribution. least squares least squares Quotation withheld because this record is not cleared for redistribution. p-value p-value Quotation withheld because this record is not cleared for redistribution. variance variance Quotation withheld because this record is not cleared for redistribution. In population cages held at 25°C the frequency of the Standard gene arrangement rose highly significantly at the expense of the other arrangements, especially Chiricahua, whereas at 16.5°C mean frequencies did not change significantly. Quotation withheld because this record is not cleared for redistribution. The rate of frequency change per generation regressed negatively on frequency, meaning each chromosome type gained when it was rare and lost when it became common. Quotation withheld because this record is not cleared for redistribution. For cages containing only Standard and Chiricahua at 25°C, relative selective values of 0.70 for ST/ST, 1.00 for ST/CH and 0.30 for CH/CH reproduce the observed changes and put equilibrium at 70 percent Standard. Quotation withheld because this record is not cleared for redistribution. With all three chromosome types present, least-squares selective values (0.43 ST/ST, 0.05 AR/AR, 0.21 CH/CH, 1.30 ST/AR, 1.00 ST/CH, 0.71 AR/CH) place equilibrium at 53 percent Standard, 34 percent Arrowhead and 13 percent Chiricahua, and the assumption that the three heterozygotes are equally fit yields impossible values. Quotation withheld because this record is not cleared for redistribution. The data cannot discriminate equal selection in the two sexes from very unequal selection: values of 1.00:1.00:0.60 in females with 0.40:1.00:0 in males fit the observations as well as the sex-averaged values. Quotation withheld because this record is not cleared for redistribution. Because the cages at 25°C and 16.5°C were stocked with sibs, the presence of change at the high temperature and its absence at the low temperature can be attributed to temperature alone. Quotation withheld because this record is not cleared for redistribution. Varying the food regime (two jars every three days versus one jar every five days) produced no consistent difference in the direction or size of the frequency changes. Quotation withheld because this record is not cleared for redistribution. In the 14th experiment Standard rose from 31 to 55 percent while Arrowhead fell from 69 to 45 percent. Quotation withheld because this record is not cleared for redistribution. The spring reversal seen in nature, in which Standard falls and Chiricahua rises, could not be reproduced in any population cage. Quotation withheld because this record is not cleared for redistribution. Measured fly dispersal rates are far too slow for migration from Keen Camp to explain the seasonal shift at Andreas Canyon 16 kilometres away. Quotation withheld because this record is not cleared for redistribution. selective disadvantage selective disadvantage Quotation withheld because this record is not cleared for redistribution. ten-day period ten-day period Quotation withheld because this record is not cleared for redistribution. temperature factor temperature factor Quotation withheld because this record is not cleared for redistribution. food regime food regime Quotation withheld because this record is not cleared for redistribution. gene arrangement gene arrangement Quotation withheld because this record is not cleared for redistribution. frequencies of chromosomes frequencies of chromosomes Quotation withheld because this record is not cleared for redistribution. gene content gene content Quotation withheld because this record is not cleared for redistribution. s=.3o, t=.7o, q=.7o — Fitted selective disadvantage of ST/ST (0.30) and of CH/CH (0.70) relative to the heterozygote, and the resulting equilibrium frequency of Standard (0.70) Quotation withheld because this record is not cleared for redistribution. 53 percent Standard, 34 percent Arrowhead and 13 percent Chiricahua — Equilibrium frequencies computed for the three-chromosome experiments at 25°C Quotation withheld because this record is not cleared for redistribution. 124 ... 157 ... II3 ... average of 131 — Estimates of the effective number of breeding parents in a cage derived from the excess variance of frequency change, from Standard, Arrowhead and Chiricahua data respectively Quotation withheld because this record is not cleared for redistribution. 300 chromosomes — Number of third chromosomes scored per monthly sample from each cage, split into six subsamples Quotation withheld because this record is not cleared for redistribution. 3·5 weeks ... 5.2 weeks — Assumed generation interval used to convert observed frequency changes into rates per generation, at 25° and at 16.5° respectively Quotation withheld because this record is not cleared for redistribution. 3ooo-sooo flies per cage — Steady-state size of the experimental cage population at room temperature with one fresh food jar every other day Quotation withheld because this record is not cleared for redistribution. 71 percent to 42 percent — Fall in Chiricahua frequency in the 13th experiment, while Standard doubled 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/31.2.125.