Finding of male-killing Spiroplasma infecting Drosophila melanogaster in Africa implies transatlantic migration of this endosymbiont

Abstract

We report the identification of male-killing Spiroplasma in a wild-caught female Drosophila melanogaster from Uganda, the first such infection to be found in this species outside of South America. Among 38 female flies collected from Namulonge, Uganda in April, 2005, one produced a total of 41 female offspring but no males. PCR testing of subsequent generations revealed that females retaining Spiroplasma infection continued to produce a large excess of female progeny, while females that had lost Spiroplasma produced offspring with normal sex ratios. Consistent with earlier work, we find that male-killing and transmission efficiency appear to increase with female age, and we note that males born in sex ratio broods display much lower survivorship than their female siblings. DNA sequence comparisons at three loci suggest that this Spiroplasma strain is closely related to the male-killing strain previously found to infect D. melanogaster in Brazil, although part of one locus appears to show a recombinant history. Implications for the origin and history of male-killing Spiroplasma in D. melanogaster are discussed.

Figure 1. Evidence for recombinant origin of a portion of the MSRO-Ug p58 sequence

DNA sequence differences observed at the 800 bp p58 locus between MSRO-Ug and MSRO-Br, and the character states of other sequenced taxa at these sites. Sites exhibiting shared character states between MSRO-Ug and one or more of the latter four taxa are boxed. Except for MSRO-Ug, these data are from Montenegro et al. (2005).