This study investigates gut microbial communities and arthropod prey composition using amplicon-based metabarcoding of faecal samples. Sequencing of 16S rRNA and COI marker genes was performed.

Countless studies have highlighted the great importance of gut microbiota for animal fitness. However, the drivers of gut microbiome composition are still not fully understood, ranging from purely environmentally sourced and variable microbiomes to those whose composition is entirely dictated by the host genotype. Admixed lineages present a particularly interesting system to study the relevance of environmental and genetic drivers in microbiome community composition. By creating novel genetic variation in hosts, hybridization and admixture may lead to rapid remolding of their microbiota, possibly contributing to the host's fitness and adaptability. Here we explore the effect of genetic admixture and dietary variation on the gut microbiome of pure-bred native and admixed invasive populations of the common wall lizard (Podarcis muralis) in southwestern Germany. Wall lizards carry a taxonomically highly predictable and stable gut microbiome, which is largely resilient against dietary composition. Gut microbiomes of pure-bred native and admixed invasive lizard populations are also very similar. No increase of microbial alpha diversity within or beta diversity between animals is found in admixed lizards. The only clear difference between pure-bred and admixed lizard populations originates in their core microbiota, which is larger and more predictable in pure-bred populations. The high stability of these lizards' gut microbiome suggests an important fitness relevance. The same holds true for the overall stability of the microbiome even after the admixture of formerly isolated genetic lineages. However, an increasing variation of the core microbiome may create evolutionary novelty in admixed populations and enhance their adaptive potential.