Observing that similar ovariole numbers have evolved independently in distinct Drosophila lineages, we asked whether this convergent evolution was due to changes in the same or different developmental processes. We discovered that similar ovariole numbers were achieved via distinct developmental mechanisms in different lineages. By using our developmental data to re-examine previous quantitative genetic data on ovariole number variation, we uncovered genetic regulators of ovariole number including the Drosophila Insulin-like receptor (InR), Hippo signaling pathway members, and the transcription factor bric-a-brac. We showed that the developmental processes underlying ovariole number are genetically separable.
In our recent work on the molecular mechanisms of interspecies ovariole number variation, we have found that evolution of insulin signaling underlies not only divergence, but also differential plasticity of ovariole number between D. melanogaster and D. sechellia. Our results suggest how differential phenotypic plasticity may explain observed patterns of ovariole number variation in different insects.
Our current work in this area focuses on identifying the genetic basis of ovariole number variation in African Drosophilids. In addition, we have begun work on the relationship between ecological niche and ovariole number variation in Hawaiian Drosophilids. These Hawaiian fruit flies have extreme ovariole numbers, ranging a full order of magnitude above and below those observed for African fruit flies. Ovariole number is also correlated with the relative abundance of larval nutrition. We are examining the developmental basis of ovariole number determination in this diverse group of species.