112 Oral - Evolution II
Friday April 08, 4:30 PM - 4:45 PM

Authors:
Jaclyn Bubnell; Cynthia Ulbing; Paula Fernandez Begne; Charles Aquadro

Affiliation: Cornell University

Keywords:
l. evo-devo; b. oogenesis

In Drosophila melanogaster, a key germline stem cell (GSC) differentiation factor, bag of marbles (bam) shows rapid bursts of amino acid fixations between sibling species D. melanogaster and D. simulans, but not in the outgroup species D. ananassae. We previously hypothesized that a change in function and/or a genetic conflict with the intracellular bacteria W. pipientis could be driving the adaptive evolution of bam, however bam function has only been defined in D. melanogaster. Here, we test the null hypothesis that bam’s differentiation function is conserved in four additional Drosophila species in the melanogaster species group spanning approximately 15 million years of divergence. Surprisingly, we demonstrate that bam is not necessary for oogenesis or spermatogenesis in D. teissieri nor is bam necessary for spermatogenesis in D. ananassae. Remarkably bam function may change on a relatively short time scale. We further report tests of neutral sequence evolution at bam in additional species of Drosophila and find a positive correlation between evidence for positive selection at bam and its essential role in GSC regulation and fertility for both males and females. Further characterization of bam function in more divergent lineages will be necessary to distinguish between bam's critical gametogenesis role being newly derived in D. melanogaster, D. simulans and D. yakuba or it being basal to the genus and subsequently lost in numerous lineages.