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  • 1
    Electronic Resource
    Electronic Resource
    Population genetics in the American Tropics XVI. Data on partial dominance of recessives in Drosophila willistoni (1982)
    Springer
    Theoretical and applied genetics 61 (1982), S. 183-191 
    Details
    ISSN: 1432-2242
    Keywords: Mutation ; Normalizing-selection ; Lethal-equivalence ; Genetic-load ; Neutral-theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Through a series of genetic load studies made on 1) samples of Drosophila willistoni from two sites in Mesitas, Colombia, it was found that the relative contributions to the total, subvital and lethal loads reflect lethal equivalences (B/A) ratios which support more the balancing theory of population structure than the neutralist theory. Moreover, measurements of population size have revealed the existance of very small demes in local populations. Under such conditions we have calculated extremely small lethal equivalence ratios in demes where probably a great deal of consanguinity takes place. We are aware that under these conditions B/A ratios cannot be very good monitors of random load measurements and, therefore, suggest a change in the mathematical formulation that take into consideration the existance of small populations. Furthermore, it appears plausible that the degree of penetrance in the heterozygous condition changes as the population structure changes. We speculate that natural populations may have unknown selective mechanisms capable of guiding unknown dominance modifiers according to the intensity of selection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00273888
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  • 2
    Electronic Resource
    Electronic Resource
    Population genetics in the American Tropics (1983)
    Springer
    Theoretical and applied genetics 65 (1983), S. 295-301 
    Details
    ISSN: 1432-2242
    Keywords: Genetic load ; Balance and mutation theory ; Lethal equivalence ; Selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary There are several Colombian populations of Drosophila pseudoobscura which have begun to show divergence. The temporal samples of Torobarroso, one of the local populations identified, demonstrate genetic “resourcefulness” and selective opportunism by fluctuating mortality. The data suggest that both balanced selection and mutational origin are necessary to account for the frequencies of drastic genes encountered. In genetic isolates there seems to exist alternatively a mutational component and a balanced — selection component. These components overcome the damage in the first instance and in the second instance, profit from the recessive load.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00276567
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Population genetics in the American tropics XVII. The biogeographical position and the sampling technique as parameters of genetic loads in Drosophila (1982)
    Springer
    Genetica 59 (1982), S. 43-51 
    Details
    ISSN: 1573-6857
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Biogeographically central populations of Drosophila melanogaster sampled with widespread and multiple sweepings generated in lethal equivalences very low indexes of heterozygous mortality which obviously produced a high B/A ratio. On the other hand, local samples from limited restricted sweepings within 10 m in diameter in a marginal population of D. willistoni from the Macarena tropical rain forest have produced the highest indexes of heterozygous mortality and consequently a very low B/A ratio. Results reported here suggest that there are ecological constraints to the lethal-equivalence method, earlier proposed by Morton, Crow and Muller (1956, Proc. natn. Acad. Sci. U.S.A. 42: 855–863). Moreover, the authors recommend that the sampling method reflect the ecological characteristic of the species under consideration. The widespread sweeping-over-large-areas method of collecting Drosophila produces, in lethal-equivalent ratios, a degree of subvitality which must be interpreted as supporting the mutation-pressure theory. However, local sampling reveals loads compatible with the balancing-selection theory. The authors find that in their natural environments D. willistoni has a local genetical structure that supports the balancing-selection theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00130813
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    Paper (German National Licenses)
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