in the spittlebug : Variable infection frequencies, but no apparent effect on host reproductive isolation.

Animals serve as hosts for complex communities of microorganisms, including endosymbionts that live inside their cells. bacteria are perhaps the most common endosymbionts, manipulating host reproduction to propagate. Many cause cytoplasmic incompatibility (CI), which results in reduced egg hatch when uninfected females mate with infected males. that cause intense CI spread to high and relatively stable frequencies, while strains that cause weak or no CI tend to persist at intermediate, often variable, frequencies. could also contribute to host reproductive isolation (RI), although current support for such contributions is limited to a few systems. To test for frequency variation and effects on host RI, we sampled several local (Fitch) (Hemiptera: Cercopidae) spittlebug populations in the northeastern United States over two years, including closely juxtaposed Maine populations with different monomorphic color forms, "black" and "lined." We discovered a group-B (Pig) infecting that diverged from group-A -like model Mel and Ri strains in -6 to 46 MYA. Populations of the sister species (Say) from Hawaii and Florida are uninfected, suggesting that acquired Pig after their initial divergence. Pig frequencies were generally high and variable among sites and between years. While phenotyping Pig effects on host reproduction is not currently feasible, the Pig genome contains three divergent sets of CI loci, consistent with high Pig frequencies. Finally, Maine monomorphic black and monomorphic lined populations of share both Pig and mtDNA haplotypes, implying no apparent effect of Pig on the maintenance of this morphological contact zone. We hypothesize acquired Pig horizontally as observed for many species, and that significant CI and variable transmission produce high but variable Pig frequencies.