Shaped by Fire: Unravelling the Impact of Fire on Lizard Gut Microbiome.

In recent decades, wildfire regimes have changed significantly, with increases in frequency, severity and area affected, leading to major habitat alterations that may impact species ecology. While fire's role in plant ecology is well studied, its effects on animal biotic interactions remain poorly understood. In northern Portugal, where wildfires are common, the native rock-dwelling lizard Podarcis lusitanicus may thrive postfire due to its preference for open rocky outcrops, which expand after fires. This suggests not only resilience but also a capacity for persistence in postfire disturbances driven by habitat preferences. However, changes in prey availability after fire induce dietary shifts in this insectivorous lizard, potentially affecting trophic interactions and, consequently, gut microbiota communities. Gut microbiota influence host fitness through effects on nutrition, immunity and behaviour; on the other hand, gut microbiota are affected by variations in diet and environment. This study assessed how fire history affects P. lusitanicus gut microbiota. Sampling occurred across 12 sites in northern Portugal, representing three fire histories: long-unburned, burned in 2016 and burned in 2022. Cloacal swabs were analysed by metabarcoding the V4 region of the 16S rRNA gene. Results showed that gut bacterial composition varied with fire history, as well as with sex, body size and diet. Females had higher microbial richness despite similar diet richness between sexes. While microbiome composition shifted, predicted microbiome function remained relatively stable, indicating both resilience and ecological flexibility in fire-prone environments. These findings enhance understanding of how lizard microbiomes respond to environmental disturbances and may help predict host and microbiota tolerance under changing fire regimes.