Unravelling intrinsic and extrinsic factors shaping the rich communities on lizard skin

Geckos have high skin bacterial diversity, even though gecko skin has antimicrobial, self-cleaning properties. To gain a better understanding of environment-animal-microbiome interactions in these reptiles, we investigated skin bacteria on seven northern Australian gecko species from five sites and two seasons (n = 234) and found support for our hypotheses of divergent communities between species, sites and seasons. Despite that support, predictor variables had low explanatory power, which increased when focusing within a site or species, explaining up to 40% and 27% of the variation among samples at a site or on a species found in multiple sites, respectively. Weather explained even less variation, as temperature and rainfall did not account for site and season differences. Low explanatory power of these variables indicates that additional factors, or stochasticity, explain much of the bacterial assemblage on geckos. Next, research is needed to determine if these low-biomass communities represent living symbionts. If so, assessing functional similarities, rather than taxonomic profiling, would clarify if bacterial communities have interactive roles with gecko hosts or represent short-lived environmental hitch-hikers and relic DNA.