An RNA virus (DCV), contagious through feeding and contact, influences Drosophila melanogaster host population dynamics. The virus is disadvantageous during the pre-reproductive period but confers definite selective advantages on survivors. The present study shows that the virus has an influence on the biotic potential of its Drosophila host population. The infected females have a high reproductive capacity, especially during the first days after eclosion. Paradoxically this reproductive advantage is positively correlated with the longevity of the imagos. Contrary to current opinion, the more productive females are the infected ones, and they live longer than the healthy females. The point that in natural populations DCV is possibly involved in evolutionary processes is discussed. The multiple interactions between Drosophila populations and DCV represents a model for further biological studies.
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