Linkage disequilibrium causing selection at a neutral locus in pooled Tribolium populations

Stam, P.

doi:10.1038/hdy.1975.3

Cited by 9 publications

(5 citation statements)

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“…4). These high differentiation measures would, strictly speaking, then not reflect purely neutral divergence but linkage between nearly neutral AFLP‐loci and selected loci (Stam 1975; Nosil et al. 2008).…”

Section: Discussionmentioning

confidence: 99%

Rapid adaptive divergence between ecotypes of an aquatic isopod inferred from F_ST–Q_ST analysis

2009

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Divergent natural selection is often thought to be the principal factor driving phenotypic differentiation between populations. We studied two ecotypes of the aquatic isopod Asellus aquaticus which have diverged in parallel in several Swedish lakes. In these lakes, isopods from reed belts along the shores colonized new stonewort stands in the centre of the lakes and rapid phenotypic changes in size and pigmentation followed after colonization. We investigated if selection was likely to be responsible for these observed phenotypic changes using indirect inferences of selection (F(ST)-Q(ST) analysis). Average Q(ST) for seven quantitative traits were higher than the average F(ST) between ecotypes for putatively neutral markers (AFLPs). This suggests that divergent natural selection has played an important role during this rapid diversification. In contrast, the average Q(ST) between the different reed ecotype populations was not significantly different from the mean F(ST). Genetic drift could therefore not be excluded as an explanation for the minor differences between allopatric populations inhabiting the same source habitat. We complemented this traditional F(ST)-Q(ST) approach by comparing the F(ST) distributions across all loci (n = 67-71) with the Q(ST) for each of the seven traits. This analysis revealed that pigmentation traits had diverged to a greater extent and at higher evolutionary rates than size-related morphological traits. In conclusion, this extended and detailed type of F(ST)-Q(ST) analysis provides a powerful method to infer adaptive phenotypic divergence between populations. However, indirect inferences about the operation of divergent selection should be analyzed on a per-trait basis and complemented with detailed ecological information.

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Section: Discussionmentioning

confidence: 99%

Rapid adaptive divergence between ecotypes of an aquatic isopod inferred from F_ST–Q_ST analysis

2009

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“…Although these theoretical expectations are wellknown, direct experimental evidence is limited. STAM (1975) demonstrated the effect of initial linkage disequilibrium on an apparently neutral marker locus in Triboliurn, and argued that both linked and non-linked fitness loci were involved. However, the populations were studied for only eight generations, so that no information was obtained on breakdown of the linkage disequilibrium.…”

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confidence: 99%

Population genetics of a sex-linked locus in Drosophila melanogaster

Barker

2009

Hereditas

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In population cages set up from laboratory stocks of white (w) and whiteblood (wbl), w frequency increased rapidly, rather than decreasing as expected. However, gene frequency changes in two environmental treatments (light and dark) were different. In the light, w frequency increased over four generations to about 0.65, remained polymorphic for about 12 generations, and then declined to zero. In the dark, w frequency increased to higher values over a longer time, but subsequent changes varied among populations. Two of these populations remain polymorphic, but at different frequencies, some 200 generations after initiation. Additional experiments involving 61 cage populations were done to test the hypothesis that the initial polymorphism resulted from associative overdominance due to linkage disequilibrium, and to analyse the nature of this disequilibrium. Results are interpreted in terms of an initial complete and complex linkage disequilibrium, with some loci affecting fitness in one environment, but not in the other. The experiments demonstrate that a complex linkage disequilibrium resulting from the mixing of previously isolated populations can lead to a variety of different polymorphisms, some of which may persist for very long periods of time, and that our understanding of the dynamics of multi‐locus systems is at a very low level.

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“…They suggest that in many, if not most, cases selection cannot be so simple as to favor a single-locus zygotic state, as if it were isolated in a neutral background. If there is value in such a view, it means that selection may indeed force a gene frequency change at an electrophoretically-detected locus, for example, without directly favoring or disfavoring the immediate gene product of that locus (e.g., see Stam, 1975). Changes in gene frequency may thus be correlated because it is the interacting system as a whole which is the unit of selection.…”

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The Unit of Genetic Change in Adaptation and Speciation

Carson¹

1976

Annals of the Missouri Botanical Garden

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Genetic variability in natural populations is very great. To a large degree, the types of variation found reflect the methods used. Thus we may recognize, segregating in ae Pop. ations, point mutations Siue which have visible or physiological effects, (2) lethal and semilethal genes, chromosome aberrations, and (4) soluble besa variability. This paper adduces cases which sugges a evolutionary heirs (adaptation or speciation or both) can occur without ШШ ОД! participation by any of the four classes of variation listed above. Thus, some cases of newly-formed species Be known in which the species pair is chromosomally homosequential. "Ot her cases show п little soluble protein (allozyme) difference (similarity coefficients of 0.95 or higher). These species appear to be much more newly formed than the classical "sibli species o t і groups of Drosophila. Nor does their biochemical similarity mean that such species differ by only a few genes. Rather, the genetic differences which characterize species when they are first formed may be numerous and largely of a regulatory nature. New gees i reni synthesized blocks of epistatically interacting polygenes may also characterize newly-formed species. A theory that the amount e oh ible protein си is primarily а function of time since the separation of two lineages is presented. This is apparently supported by allozyme data on eight species of о inhe biting Hawaiian а of successively younger times of origin.Ten years ago, systematic and evolutionary biology suddenly found itself wedded to molecular genetics. This strange affair came about because of the application of the new electrophoretic techniques to the genetic state of individuals in natural and artificial populations. The effect of this new biochemical genetics has been galvanic, especially in population genetics. Although traditionally strong in theory, this field had been struggling along for years with techniques of genetic analysis which could be applied to only a few kinds of organisms. Under the influence of these new techniques, however, both systematics and ecology have become deeply involved in a biochemical approach. Revolutionary ideas have been popping up on every hand. The purpose of the present discussion is to take a brief look back over the last few eventful years to see if major new concepts may be discerned. ADAPTATIONHow does the natural genetic variability within a species relate to the immediate needs of the organism? To what extent do the genes track the environment? First to be discovered were the recessive "visible" mutations which can be segregated out, from specimens collected in the wild, by inbreeding their progeny in the laboratory. Following this, variants which are manifested cytologically, like inversions and translocations, came to light. Many of these were shown to exist as balanced polymorphisms in nature. Still later, as genetic techniques became more sophisticated, precise methods revealed a further wealth

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Linkage disequilibrium causing selection at a neutral locus in pooled Tribolium populations

Cited by 9 publications

References 6 publications

Rapid adaptive divergence between ecotypes of an aquatic isopod inferred from F_ST–Q_ST analysis

Rapid adaptive divergence between ecotypes of an aquatic isopod inferred from F_ST–Q_ST analysis

Population genetics of a sex-linked locus in Drosophila melanogaster

The Unit of Genetic Change in Adaptation and Speciation

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Linkage disequilibrium causing selection at a neutral locus in pooled Tribolium populations

Cited by 9 publications

References 6 publications

Rapid adaptive divergence between ecotypes of an aquatic isopod inferred from FST–QST analysis

Rapid adaptive divergence between ecotypes of an aquatic isopod inferred from FST–QST analysis

Population genetics of a sex-linked locus in Drosophila melanogaster

The Unit of Genetic Change in Adaptation and Speciation

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Product

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Rapid adaptive divergence between ecotypes of an aquatic isopod inferred from F_ST–Q_ST analysis

Rapid adaptive divergence between ecotypes of an aquatic isopod inferred from F_ST–Q_ST analysis