OVIPOSITION BEHAVIOUR IN FOUR SPECIES OF DROSOPHILA
Oviposition site selection plays a central role in the evolutionary ecology of Drosophila, due to its high relation with the pre-adults fitness since the site selection determines the interactions between the species sharing common resources. Drosophila subobscura Collin which was detected in Chile for the first time in 1978, was found coexisting in the wild, as adults, over apple and raspberry, with D. hydei, D. immigrans and D. melanogaster. It was observed that raspberry has been used only by Drosophila subobscura as a breeding site; meanwhile sharing apple with the others. Our principal purpose was to shed light on the ecological significance of the new species oviposition behaviour; analysing also some of the preference-performance relationship. Two experiments of non-choice and choice, were carried out. The results showed that all species used both substrates as a breeding site. However, D. subobscura and D. melanogaster chose significantly raspberry, whereas D. immigrans and D. hydei preferred apple. In relation to preference-performance, only D. melanogaster expressed that positively in terms of short development time and high viability. The physical characters of the substrate could explain the oviposition preference. These results constitute the first empirical evidence that D. subobscura is constantly colonising new breeding sites, if it is known that raspberry has been cultivated for one decade.