The wild side of life: Drosophila reproduction in nature.

Drosophila species vary in the rates at which females remate and the number of sperm they receive in the laboratory. In species such as D. melanogaster and D. pseudoobscura, in which females receive thousands of sperm and remate infrequently compared with species such as D. hydei and D. nigrospiracula, where females receive only a few hundred sperm and remate many times in a day, wild caught females should produce far more progeny. We tested this prediction by collecting, directly from nature, females of six species whose remating rates and number of sperm received vary from high to low and assessing the proportion of females with sperm and the number of progeny females produce. Over 95% of D. pseudoobscura and D. melanogaster females were inseminated while far fewer of the other species contained any sperm. In addition, D, pseudoobscura females produced progeny for over two weeks, D. melanogaster for over a week, while D. hydei and D. nigrospiracula females ran out of sperm after 1-2 d. These observations suggest extreme sperm limitation in these latter species.