The development of larval foraging behaviour in Drosophila pavani, D. gaucha and their reciprocal hybrids

The development of larval foraging behaviour in the sibling species D. pava ni and D. gaucha and in their reciprocal interspecific hybrids was analysed . The goals were: (i) to identify interspecific differences in developmenta l patterns of larval behavioural organization, and (ii) to study changes in the frequency of ecologically relevant behaviours during larval ontogeny. Hybridization changed the developmental pathway of feeding and locomotor ac tivity, suggesting genetic divergence for foraging behaviour between the sp ecies. Larval turning and bending were not affected by hybridization, sugge sting a similar genetic architecture for each of these activities in both s pecies. Retreat and rearing were observed during the whole of larval period in D. pavani, while these behaviours were rarely observed in D. gaucha and the hybrids, suggesting dominance of the gaucha genome over that of pavani . The behavioural organization of D. pavani larvae is related to ontogeny; this was not observed in gaucha and in species hybrid larvae, suggesting ag ain a dominance of this genome over that of D. pavani. The results are disc ussed in terms of evolutionary developmental genetics of foraging behaviour of Drosophila larvae.