1985. A genetic analysis of path length and pupation height in a natural population of Drosophila melanogaster. Can. J. Genet. Cytol. 27: 334-340.Behaviour-genetic studies using laboratory strains of Drosophila are often criticized because the results cannot be generalized to natural populations. The genetic component of variation in two prepupal behaviours was studied for strains derived from a natural population of Drosophila melanogaster. These strains showed a second-chromosome based contribution to differences in path length (the distance a larva crawls in a yeasted culture dish) with the long path length phenotype dominant over the short. Differences in pupation height (the distance a larva pupates above the surface of the medium) were affected not only by the second chromosomes but also by the third pair of chromosomes. The second pair influenced the differences in pupation height threefold more than the third. Intermediate pupation heights were found in the reciprocal crosses. While path lengths could be replicated in their absolute scores over different days, pupation heights could only be replicated in their relative scores. BAUER, S. J., et M. B. SOKOLOWSKI. 1985. A genetic analysis of path length and pupation height in a natural population of Drosophila melanogaster. Can. J. Genet. Cytol. 27: 334-340.Les ktudes de comportement gknetique avec souches de Drosophilu de laboratoire sont souvent critiqukes vu que, gknkralement, les resultats obtenus ne peuvent 2tre appliques aux populations naturelles. La composante gknktique de variation a kt6 ktudike en rapport avec deux comportements prk-pupes chez des souches dkrivees d'une population naturelle de Drosophila melanogaster. Ces souches ont rkvklk la contribution d'une seconde paire de chromosomes face aux diffkrentes longueur de trajets accomplis par les larves (c.-a-d. la distance couverte par une larve sur culture en pot contenant de la levure); de fait, les phknotypes a trajets longs ont domink les phknotypes a trajets courts. Les diffkrences en hauteur de pupation (c.-a-d. la distance au-dessus de la surface du milieu oh les larves vivent leur stade nymphal) ont ete affectkes non seulement par la seconde paire de chromosomes, mais aussi par la troisieme paire de chromosomes. Toutefois, les differences en hauteur de pupation ont kt6 trois fois plus influenckes par la seconde paire de chromosomes que par la troisikme paire. Des hauteurs intermkdiaires de pupation ont kt6 observkes chez des croisements reciproques. Tandis que les longueurs de trajet pouvaient 2tre rkpliqukes en valeurs absolues a des jours diffkrents, les hauteurs de pupation n'ont pu Ctre rkpliqukes qu'en valeurs relatives.

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The inheritance of Drosophila melanogaster larval pupation behaviour is investigated in sixteen reciprocal crosses between field collected lines. These lines were made isogenic for the two major autosomes enabling the data to be analyzed using contrast analysis of variance and biometrical genetic analysis. Results of both analyses showed that the trait "pupation distance", the distance larvae pupate from food, fits a simple additive model of inheritance with no dominance. A chromosomal analysis showed that both the second and third chromosomes act additively on pupation distance and that the third pair of chromosomes had a much larger effect than the second. Significant variability exists in the distance D. melanogaster larvae pupate from fruit in nature. This phenotypic variation results from both heritable variation and variation from environmental sources. When the moisture content of the environment surrounding food is modified, gene by environment interactions also contribute to variation in the phenotype. Selective pressures which may act on larval differences in pupation site choice are discussed.

Isofemale lines of Drosophila, recently sampled from nature, were used to study the within-and between-line phenotyplc variability of a preadult behavior. The locomotory component of larval foraging behavior was quantified by measuring the length of the path traversed by a foraging 3rd Instar larva on a yeasted dish. Significant between-line variation for this behavior was found in Drosophila melanogaster and in D. pseudoobscura. Matings between lines with extreme phenotypes indicated a relatively simple genetic basis for differences in larval foraging behavior.

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