PT  - JOURNAL ARTICLE
AU  - William R. Conner
AU  - Mark L. Blaxter
AU  - Gianfranco Anfora
AU  - Lino Ometto
AU  - Omar Rota-Stabelli
AU  - Michael Turelli
TI  - Genome comparisons indicate recent transfer of &lt;em&gt;w&lt;/em&gt;Ri-like &lt;em&gt;Wolbachia&lt;/em&gt; between sister species &lt;em&gt;Drosophila suzukii&lt;/em&gt; and &lt;em&gt;D. subpulchrella&lt;/em&gt;
AID  - 10.1101/135475
DP  - 2017 Jan 01
TA  - bioRxiv
PG  - 135475
4099  - http://biorxiv.org/content/early/2017/05/08/135475.short
4100  - http://biorxiv.org/content/early/2017/05/08/135475.full
AB  - Wolbachia endosymbionts may be acquired by horizontal transfer, by introgression between closely related species, or by cladogenic retention during speciation. All three modes of acquisition have been demonstrated, but their relative frequency is largely unknown. Drosophila suzukii and its sister species D. subpulchrella harbor Wolbachia, denoted wSuz and wSpc. These Wolbachia are very closely related to wRi, identified in California populations of D. simulans. Nevertheless, these variants differ in the phenotypes they induce: wRi causes significant cytoplasmic incompatibility (CI) in D. simulans, but CI has not been detected in D. suzukii or D. subpulchrella. Draft genomes of wSuz and wSpc show that they differ by only 0.004% in their coding sequences; they are sisters relative to wRi, from which they differ by 0.015%. Despite uncertainties about molecular divergence rates for Drosophila and Wolbachia, wSuz and wSpc are not plausible candidates for cladogenic transmission, as their divergence is too recent compared to their hosts’ – by at least a factor of 100. These three wRi-like Wolbachia have different copy numbers of orthologs of genes postulated to contribute to CI, and also display several single nucleotide differences in the CI loci. These differences may account for the different levels of CI they produce. We discuss the general problem of distinguishing alternative modes of Wolbachia acquisition, focusing on the difficulties posed by limited knowledge of variation in rates of molecular evolution for host nuclear genomes, mitochondria and Wolbachia.