Drosophila pseudoobscura populations of Central Mexico are chromosomally highly polymorphic. Five gene arangements in the third chromosome are endemic, including the two newly described in the present article. The phylogenetic tree of the gene arrangements known in the species is shown in Figure 1. The ones found in Central Mexico all belong to the Santa Cruz "phylad", while in the northern part of the species area both Santa Cruz and Standard phylads are widespread. Some inferences concerning the evolutionary history of the species are presented.

Animals↗

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Functional relationships between genotypes and environments in behavior. Effects of different kinds of early social experience on interstrain fighting in male mice.

Comparisons are made of the interstrain fighting behavior of adult male mice from two inbred strains (ST-albino; CBA-black-agouti), raised in one of three postweaning social situations: 1) isolated from other males, 2) reared with males of the same strains, or 3) reared with males of the opposite strain. Using the fighting behavior of isolated males as a baseline, it is found that each type of early social experience affects the fighting behavior of the males from each of the two inbred strains differently, indicating that the functional relationships between genotype and environment studied in these experiments are nonadditive. The importance of these results in describing the norm of reaction of a behavioral phenotype and in extrapolating data from one experiment to another is discussed.

Aggression↗

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Sexual selection in mice. VI. Effects of fostering.

Individually, 10 male mice of both the albino (ST/bJ) and black-agouti (CBA/J) strains were taken at birth, fostered to females of the other strain, and reared with their litters. At weaning each male was paired with one of its foster brothers and placed in a separate cage. When the males were 90 days of age, a single albino (ST/bJ) female was placed in each pen. Ten litters were obtained from each competition cage, yielding a total of 100 litters for each type of fostering. In those cases where CBA males had been reared with ST litters, both males were equally successful in reproduction. However, in the reverse situation, where ST males had been reared with CBA litters, the ST males enjoyed a distinct reproductive advantage. These results are compared to those obtained in a previous sexual selection experiment, using the same strains of mice but without fostering. In addition, the results of fighting experiments between males from these strains and the implications of those results for the present study are discussed.

Animals↗

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Effects of selection for decreased movement through the Drosophila geotaxis maze.

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Animals↗

PubMedDate not supplied

Chromosomal and behavioral studies of Mexican Drosophila. III. Inversion polymorphism of D. pseudoobscura.

Four new gene arrangements of chromosome 3 of Drosophila pseudoobscura are reported, as well as an updated phylogenetic sequence of the inversion polymorphism in this species. Evidence that the Tree Line gene arrangement of chromosome 3 was the original form in D. pseudoobscura, and that Central Mexico is the center of distribution of this species is discussed.

Animals↗

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Desiccation resistance in two species of Drosophila.

Three populations of Drosophila pseudoobscura, each one represented by 12 isofemale lines, and one laboratory strain of D. melanogaster were tested for desiccation resistance at two time periods. Except in the case of one population of D. pseudoobscura, the ability to withstand drying was significantly greater in females than in the corresponding males. The males of the three populations of D. pseudoobscura differed significantly among themselves in their resistance to desiccation, as did the females. The females of D. melanogaster exhibited a consistently higher survival rate than those of D. pseudoobscura, but not the males. These results are discussed with reference to the third chromosome inversion polymorphism of D. pseudoobscura and the cosmopolitan distribution of D. melanogaster.

Adaptation, Physiological↗

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Studies of sibling Drosophila species from Laguna Verde, Veracruz, Mexico: I. Species frequencies, viability, desiccation resistance, and vagility.

The sibling species Drosophila melanogaster and D. simulans were collected at Laguna Verde, Veracruz, Mexico. D. melanogaster was found in significantly greater frequency than was D. simulans. Ten isofemale lines of each species were tested for egg to adult viability, desiccation resistance, and vagility. D. melanogaster surpassed D. simulans in all three characteristics. The findings are discussed with reference to the climatic conditions at Laguna Verde and the expected effect of such an environment on the relative frequencies of these species. The dichotomous results in regard to desiccation resistance and vagility that were observed between recently collected D. melanogaster and the Oregon-R laboratory stock of that species are also discussed.

Animals↗