Genetic variation for oviposition behavior in Drosophila melanogaster. I. Quantitative genetic analysis of insertion behavior

Neurogenetics of female reproductive behaviors in Drosophila melanogaster

We follow an adult Drosophila melanogaster female through the major reproductive decisions she makes during her lifetime, including habitat selection, precopulatory mate choice, postcopulatory physiological changes, polyandry, and egg-laying site selection. In the process, we review the molecular and neuronal mechanisms allowing females to integrate signals from both environmental and social sources to produce those behavioral outputs. We pay attention to how an understanding of D. melanogaster female reproductive behaviors contributes to a wider understanding of evolutionary processes such as pre- and postcopulatory sexual selection as well as sexual conflict. Within each section, we attempt to connect the theories that pertain to the evolution of female reproductive behaviors with the molecular and neurobiological data that support these theories. We draw attention to the fact that the evolutionary and mechanistic basis of female reproductive behaviors, even in a species as extensively studied as D. melanogaster, remains poorly understood.

Ecology of colonizing populations of the figfly Zaprionus indianus (Diptera, Drosophilidae) in Porto Alegre, Southern Brazil

Ecological parameters such as trophic niche overlap and niche breadth were computed from the frequency of all drosophilid species collected in 2001 and 2002, in the urban area of Porto Alegre city, Brazil. Independently of place, drosophilids community composition and components breeding or feeding sites, the highest frequencies of Zaprionus indianus (Gupta, 1970) were obtained during seasons with higher average temperatures, especially during summer. From a total of the 19,146 individuals of Z. indianus sampled, 80% were found in this season. The data of trophic niche breadth suggest a higher opportunism of adult flies in feeding substrate use, but the females are still selective in oviposition substrate choice. For the values of niche overlap, only for some species, did we find any correlation between these and species richness and/or number of resources, and the most of the correlation values considering breeding and feeding sites were positive. The colonization of Z. indianus in Porto Alegre could be leading to adjustments in the survival strategies of the resident species, but it is possible that many species have conditions for coexisting with the invader.

Conditioning to ethanol in the fruit fly-a study using an inhibitor of ADH

To identify processes involved in the choice of ethanol by adult Drosophila, flies homozygous Adh(F), reared in the absence of alcohol were placed in contact with: a) an ethanol-free medium, b) a medium containing ethanol, c) a medium supplemented with 4-methylpyrazole (4-MP, an inhibitor of the ADH pathway), d) a medium containing ethanol and 4-MP. The choice of ethanol over a medium without ethanol was evaluated by measuring the duration of extension of the proboscis of the flies in each of the media. A slight preference for the ethanol-supplemented medium was observed in the naive flies, which was enhanced by previous exposure to ethanol. Exposure to ethanol and 4-MP, however, led to an avoidance of ethanol. There was a reduction in ADH activity on treatment of the flies with 4-MP, and signs of malaise (reduced locomotor activity, loss of balance) were observed in the flies who ingested both ethanol and inhibitor. We concluded that the preference for ethanol stems from an associative learning related to ethanol utilization. Inhibition of enzymes of ADH pathway led to a conditioned aversion due to disturbance of ethanol metabolism giving rise to malaise.

A diallel analysis of gregarious oviposition in Drosophila melanogaster

Drosophila females exhibit gregarious oviposition. This behaviour was analysed by a diallel cross. The trait shows considerable additive genetic variation and a significant dominant effect. A variance and covariance analysis suggests that ebony and taxi strains contain the most dominant alleles. Some maternal effect may also be present. This genetical architecture is in line with previous studies of selection and hybridization of the lines selected for high and low gregarious oviposition in Drosophila melanogaster females.

Genetic variation for oviposition behavior in Drosophila melanogaster. II. Oviposition preferences and differential survival

Several behavioral traits connected with oviposition were studied in Drosophila melanogaster strains which ahd been kept on regular and ethanol-supplemented food. All strains preferred food with a low agar content for oviposition, though this tendency was more pronounced in an ethanol-adapted strain. Oviposition on regular and ethanol-supplemented food was tested both under choice and no-choice conditions. Though dependent on the alcohol dehydrogenase genotype adapted strains in general preferred ethanol food, while control strains preferred regular food. There was a strong tendency for oviposition on the vertical sides, when food blocks were offered. This tendency was more pronounced in the ethanol adapted strains. For egg insertion (for which the genetic basis was analyzed in the preceding paper; Kamping and van Delden, 1990), it was shown that inserted eggs laid on ethanol food hatched more often than noninserted eggs. The adaptive significance of the genetic differences in oviposition behavioral traits is discussed.