Yeast Communities Associated with Diptera of the White Sea Littoral

Relationship between symbiotic yeast and Diptera insects are studied mainly on fruit flies (Drosophilidae). Evolutionary experiments showed that changes in the composition of the yeast microbiota vectored by flies in their gut and on the body surface contributes to the adaptation of laboratory Drosophila populations to the high-salt growth medium. Although saline substrates are not commonly used by Drosophilidae in nature, species adapted to such substrates are known in other families of Diptera. Yeast communities associated with these species are studied insufficiently. This is the first report on the yeast communities associated with two Diptera species living near the White Sea, Paracoenia fumosa (Stenhammar, 1844) (Ephydridae) and Fucellia fucorum (Fallen, 1819) (Anthomyiidae). Their larvae develop in the coastal saline lagoons and in algae driven ashore. The P. fumosa yeast microbiota includes opportunistic species Pichia kluyveri Bedford ex Kudryavtsev, 1960 and P. kudriavzevii Boidin, Pignal, Besson, 1965 and is characterized by its highly variable abundance (the number of colony-forming units varies widely in different individuals). F. fucorum is characterized by a more stable yeast community, including species common in White Sea algae and coastal waters (Debaryomyces hansenii (Zopf) Lodder, Kreger-van Rij, 1952, Metschnikowia zobellii (van Uden, Castelo-Branco) van Uden, 1962, and M. bicuspidata (Metschnikoff) Kamienski, 1899). These two species of littoral flies shared no common yeast species. Moreover, none of the yeast species found in the littoral flies was detected in the evolutionary experiment on the adaptation of Drosophila to the high-salt growth medium (the similarity is limited only to the Pichia genus level). Contrasting differences in the yeast microbiome of two ecologically similar littoral species of Diptera may indicate, on the one hand, specificity, and, on the other, evolutionary plasticity of the relationship between salt-tolerant flies and yeast.