Connecting neuromodulation, brain development, and life history adaptation underlying ongoing ecological speciation in Rhagoletis pomonella

In temperate regions, life history timing is one of the most important ecological barriers which separates host plant and their specific insects. We are studying the neural mechanism for ecological speciation in Rhagoletis sp. (Diptera: Tephritide). This speciation is being observed over the past 300 years in North America. The introduction of domesticated apples (Malus pumila) by European colonists around 1800-1850 caused a shift in host preference by these flies from their native host downy hawthorn (Crataegus mollis). However, the question of how such a rapid and specific change in host preferences could occur in such a short period of evolutionary time remains unanswered. In insects, metamorphosis brings profound reorganization and transformation of the nervous system. Neurotransmitters, neurohormones are known to play a vital role in development and behavior.

Apple and Hawthorn fly undergoes pupal diapause during winter, apple flies initiate and terminate diapause at a different time than hawthorn flies. Here, we hypothesize that neuromodulators, which are known to regulate different behaviors in insects, could also be responsible for affecting timing during developmental stages and host preference in these races.

Using liquid chromatography-mass spectrometry (LC-MS), I quantified the levels of neurotransmitters from the brain of developing pupal and adult R. pomonella. The quantification of neurotransmitters shows significant differences in certain chemicals, tyrosine, and octopamine. our data suggest apple flies exhibit adult neurogenesis nearly three weeks faster than hawthorn flies (day 20 vs. day 40), but their neurotransmitter production does not increase accordingly.