On the spread of microbes that manipulate reproduction in marine invertebrates

Bacterial symbionts are functionally integral to animal reproduction and development, some of which have evolved additional mechanisms to override these host programs. One habitat that is increasingly recognized to contain phylogenetically related lineages of reproductive manipulators is the ocean. The reproduction of marine invertebrates often occurs by free-spawning instead of by the physical contact of copulation in terrestrial systems. We developed an integrated model to understand whether and when microbes that manipulate host reproduction by cytoplasmic incompatibility, feminization, and male killing spread within populations of free-spawning marine invertebrates. Our model support three primary findings. First, sex ratio distortion leads to suboptimal fertilization and zygote production in planktotrophs (feeding larvae), but enhance these processes in lecithotrophs (nonfeeding larvae). Second, feminization and a combination of male killing plus enhanced growth are effective at sp...