[Peculiarities of the courtship song in the Drosophila melanogaster populations adapted to gradient of microecological conditions].

In theory of evolution, two chief scenarios of development of sexual isolation--allopatric and sympatric, which act respectively under conditions of geographic separation or without it. Differences in the courtship behavior and in the used signals can lead to reproduction isolation and prevent gene exchange between sympatric populations or species, in which postcopulational barrier are absent. The previous studies of natural Drosophila populations inhabiting the opposite, ecologically contract slopes of evolutional canyon (vicinities of the brook Open in the mountain ridge Karmel, Israel) revealed statistically significant differences between them by the complex of adaptive and behavioral parameters including courtship behavior and choice of partner for copulation. Astonishingly, differentiation of two populations has appeared in spite of a very small distance between two slopes. Here we report the statistically significant differences between males from the opposite slopes in characteristics of the courtship song that is one of signals serving for recognition by female of sexual partner of her species. We suggest that these differences can underlie the earlier revealed female discriminational behavior and can reflect different adaptive strategies in the populations inhabiting opposite canyon slopes.

[Novel memory mutants in Drosophila: behavioral characteristics of the P-insertional mutant in the Ent2P locus].

The Drosophila mutant P124, carrying insertion of P(lacW) vector in the second chromosome on the background of the w mutation in the X chromosome, was previously isolated as showing memory deficiency after courtship conditioning. Here we report additional features of the mutant phenotype: (1) abnormal adaptation to dark-light transition; (2) impaired perception by males of nuances of visual image of a female, specifically, of her fine movements such as preening and ovipositor extrusion; (3) subnormal performance index after odor-shock conditioning. These abnormalities are not related to a deficit of the eye screening pigments because they are also revealed on the background of the normal w+ allele in the X chromosome. The visual and cognitive impairments are independent pleiotropic effects of the mutation. The mutation is caused by insertion of the P vector 12 nucleotides upstream of the transcription start of the gene Ent2 (equilibrative nucleoside transporter 2). Ent2(P124) is the second mutant allele of this gene found in Drosophila. The genetic variability in Ent2 locus should be considered as a factor of risk for development of mental retardation and disorders of visual perception.

Sexual and reproductive behaviour of Drosophila melanogaster from a microclimatically interslope differentiated population of "Evolution Canyon" (Mount Carmel, Israel).

The strong microscale interslope environmental differences in "Evolution Canyon" provide an excellent natural model for sympatric speciation. Our previous studies revealed significant slope-specific differences for a fitness complex of Drosophila. This complex involved either adaptation traits (tolerance to high temperature, different viability and longevity pattern) or behavioural differentiation, manifested in habitat choice and non-random mating. This remarkable differentiation has evolved despite a very small interslope distance (a few hundred metres only). Our hypothesis is that strong interslope microclimatic contrast caused differential selection for fitness-related traits accompanied by behavioural differentiation and reinforced by some sexual isolation, which started incipient speciation. Here we describe the results of a systematic analysis of sexual behaviour in a non-choice situation and several reproductive parameters of D. melanogaster populations from the opposite slopes of "Evolution Canyon". The evidence indicates that: (i) mate choice derives from differences in mating propensity and discrimination; (ii) females from the milder north-facing slope discriminate strongly against males of the opposite slope; (iii) both sexes of the south-facing slope display distinct reproductive and behavioural patterns with females showing increased fecundity, shorter time before remating and relatively higher receptivity, and males showing higher mating propensity. These patterns represent adaptive life strategies contributing to higher fitness.