A Tangled Web: The Dynamics of Endosymbiotic Infections in a Linyphiid Spider

Many arthropods are infected with bacterial endosymbionts that manipulate host reproduction, but few bacterial taxa have been shown to cause such manipulations. Mermessus fradeorum (Linyphiidae) is a sheet-weaving spider that displays both feminization and cytoplasmic incompatibility (CI). To correlate reproductive manipulations to endosymbionts, I surveyed the bacterial community of M. fradeorum using high throughput sequencing and found that individuals can be infected with up to five different strains of bacteria from the genera Wolbachia, Rickettsia, and Rickettsiella. Rickettsiella was found in all 23 tested spider matrilines. I used antibiotic curing to generate uninfected matrilines that I reciprocally crossed with individuals infected with Rickettsiella. Only 13% of eggs hatched when uninfected females were mated with Rickettsiella-infected males, while at least 83% of eggs hatched in the other cross types. This is the first documentation of Rickettsiella, or any Gammaproteobacteria, causing CI. I then characterized symbiotypes of M. fradeorum in central Kentucky to determine the variation in endosymbiotic community composition among host populations. Overall, regional populations of M. fradeorum share endosymbiont strains, but the frequency of infection varied among populations. These results suggest that endosymbiotic infections of M. fradeorum are dynamic and that populations are composed of a mixture of symbiont-induced phenotypes