Geographical, Ecological, and Genetic Drivers of Gut Microbial Diversity in Native and Invasive Minnows (Leuciscidae: <i>Cyprinella</i>)

The gut microbiome is important for many physiological processes that are critical in the adaptation of an animal to its environment. Conversely, abrupt ecological changes, as in the colonisation of a new territory, may also influence the microbiome. Therefore, anthropogenic introductions of invasive species offer a natural model in which to study these relationships. We compared the gut microbiomes (16S rRNA gene) of four freshwater fish species of the genus Cyprinella, including both native and introduced populations of the prolific invader C. lutrensis, to investigate if differences in their diversity and structure are determined by their host or depend more on the ecology and geographical location where they occur. Our results suggest that at this taxonomic level, the external environment of the fish is the strongest corollary of microbial diversity and community composition of the gut, followed to a lesser extent by species identity and genetic factors. Our findings emphasise the dynamic nature of the minnow gut microbiome, with high individual variation and rapid changes over time. We also found that new invasions may reduce the invader's gut microbiome alpha diversity while not conferring any clear distinction compared with cohabiting native species. This research addresses the perennial question of whether nature or nurture plays a greater role in shaping the gut microbiome, revealing the intricate interplay of factors and scales involved.