Microbial communities of lizard cloaca and eggshells

Beneficial microbes can be vertically transmitted from mother to offspring in many organisms. In oviparous animals, bacterial transfer to eggs may improve egg success by inhibiting infection by pathogenic microbes in the nest environment. An important mechanism of vertical transfer may be the passage of the egg through the maternal cloaca during oviposition itself, especially in species that lack behavioral transfer mechanisms due to the absence of parental care. We examined these questions in the striped plateau lizard, Sceloporus virgatus, which lays eggs at the peak rainy season (and high fungal growth) and provides no post-laying care to eggs. The sequences deposited here are the result of amplification of the 16S rRNA genes gathered from cloacal swabs of females at the time of field collection and after a few days in captivity, eggshells of eggs that were oviposited or dissected, as well as field and lab controls and mock communities. Our results indicate that female S. virgatus lizards do indeed transfer beneficial microbes from their cloaca onto their eggs during oviposition, and that these microbes reduce fungal colonization and infection of eggs during incubation. The microbes increase female fitness by improving hatch success and offspring phenotype. Cloacal transfer of egg-protective bacteria may be common among oviparous species, and may be especially advantageous to species that lack parental care.