Wild African Drosophila melanogaster Are Seasonal Specialists on Marula Fruit

Autor: Marcus C. Stensmyr, Anders Enjin, Erling Jirle, Vedika Ramesh, John E. Pool, Paul G. Becher, Suzan Mansourian, Guillermo Rehermann
Rok vydání: 2018
Předmět:
Zdroj: Current Biology. 28:3960-3968.e3
ISSN: 0960-9822
DOI: 10.1016/j.cub.2018.10.033
Popis: Summary 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.
Databáze: OpenAIRE