Nonadaptive microbiota in molluscivore pupfish
We found enrichment of the families Rhodobacteraceae andPlanctomycetacia within the molluscivore gut from both lake
populations (Figure 5). However, these families have no clear role in
anything related to mollusc digestion or even increased levels of
protein, lipids, or chitin in the diet (due to some molluscivores
specializing on ostracods during periods of abundance). Taxa from these
taxonomic group are known to be found within aquatic environments (Simon
et al. 2017; Yilmaz et al. 2016). Marine Rhodobacteraceae have a
key role in biogeochemical cycling, make up about 30% of bacterial
communities in the pelagic environment, and generally have a mutualistic
relationship with eukaryotes providing vitamins to these groups (Simon
et al. 2017). Both families are known for aquatic cellulose-decomposing
taxa (Ringø et al. 2016; Kim et al. 2016), which suggests this
microbiome shift may help more with macroalgae digestion rather than
molluscs, despite previous observations that macroalgae forms the
largest component of the generalist pupfish diet in the hypersaline
lakes of San Salvador Island, Bahamas (Martin and Wainwright 2013).