Wild African Drosophila melanogaster Are Seasonal Specialists on Marula Fruit

Curr Biol. 2018 Dec 17;28(24):3960-3968.e3. doi: 10.1016/j.cub.2018.10.033. Epub 2018 Dec 6.


Although the vinegar fly Drosophila melanogaster is arguably the most studied organism on the planet, fundamental aspects of this species' natural ecology have remained enigmatic [1]. We have here investigated a wild population of D. melanogaster from a mopane forest in Zimbabwe. We find that these flies are closely associated with marula fruit (Sclerocarya birrea) and propose that this seasonally abundant and predominantly Southern African fruit is a key ancestral host of D. melanogaster. Moreover, when fruiting, marula is nearly exclusively used by D. melanogaster, suggesting that these forest-dwelling D. melanogaster are seasonal specialists, in a similar manner to, e.g., Drosophila erecta on screw pine cones [2]. We further demonstrate that the main chemicals released by marula activate odorant receptors that mediate species-specific host choice (Or22a) [3, 4] and oviposition site selection (Or19a) [5]. The Or22a-expressing neurons-ab3A-respond strongly to the marula ester ethyl isovalerate, a volatile rarely encountered in high amounts in other fruit. We also show that Or22a differs among African populations sampled from a wide range of habitats, in line with a function associated with host fruit usage. Flies from Southern Africa, most of which carry a distinct allele at the Or22a/Or22b locus, have ab3A neurons that are more sensitive to ethyl isovalerate than, e.g., European flies. Finally, we discuss the possibility that marula, which is also a culturally and nutritionally important resource to humans, may have helped the transition to commensalism in D. melanogaster.

Keywords: Drosophila; commensalism; host plants; odorant receptors; olfaction; specialization.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Africa, Southern
  • Anacardiaceae / chemistry*
  • Animals
  • Chemotaxis*
  • Drosophila melanogaster / physiology*
  • Feeding Behavior
  • Female
  • Fruit / chemistry*
  • Receptors, Odorant / physiology*
  • Seasons


  • Receptors, Odorant