Bacterial community composition of Ampullaceana balthica. Biogeography of Ampullaceana balthica

Factors driving the distribution of bacteria composition are poorly understood, and the role of geographical patterns that are indicative for limited dispersal is still debated. Host associated bacteria face a different set of dispersal challenges since specific hosts associated bacteria often depend on their vectors for bacterial dispersal. Here we investigate the influence of biogeographic boundaries on the bacterial diversity and composition of snail-gastrointestinal tract bacterial communities compared to water and sediment bacterial communities using 16S rRNA gene sequencing. The bacterial communities of the three substrates (in the snail gastrointestinal samples, water, sediment) taken in Estonia, Denmark and Northern Germany differed between countries. The overlap of sequencing variants (ASVs) of the snail gastrointestinal samples between countries was lower compared to sediment and water, indicating country specific bacterial communities. This suggests that biogeographic boundaries constrain the distribution of gastrointestinal bacterial communities more than for water or sediment where a large core set of microbes between counties were found. Within a country, the number of specific ASVs were lowest for gastrointestinal samples suggesting a large overlap with local bacterial communities. Hence the gastrointestinal bacterial community seems to select specific ASVs from the local bacterial community and therefore local differences in the vegetation and climatic between the countries have a strong influence on the gastrointestinal bacterial community.