Microbial communities associated with endangered West Texas springsnails and their potential roles in conservation

ABSTRACT Desert springs are one of the most threatened ecosystems globally. Those in Southwestern North America support high numbers of threatened and endemic species. Human activities present the greatest threats to springs and the organisms they support. Freshwater snails in the genera Pyrgulopsis and Tryonia are two groups of such organisms, representing diverse and threatened groups of springsnails in the Southwestern United States. Desert springs also harbour unique microbial diversity that faces similar threats from water usage and freshwater habitat degradation. Understanding springsnails and the bacteria they host represent potential exemplars for interdisciplinary conservation efforts. We studied the bacterial communities associated with eight threatened springsnail species, five Pyrgulopsis and three Tryonia, each collected from a unique spring. Near-complete ribosomal 16S ribosomal DNA (rDNA) sequences were generated from each sample using PacBio chemistry, analysed in QIIME 2, and taxonomically classified using a SILVA database. Shannon diversity did not significantly differ across snail species and spring combinations; however, analyses of UniFrac distances suggested differences between species and collection sites. Mycoplasmatota, Pseudomonadota and Cyanobacteriota were the most abundant bacterial phyla while Mycoplasmataceae, Leptolyngbyaceae and Staphylococcaceae were the most abundant families. Each snail species and collection site possessed at least one bacterial family that could serve as a diagnostic bioindicator for that combination. Only 11.9% of the bacterial OTUs matched to the NCBI prokaryotic 16S rDNA reference database at ≥99% similarity. A multivariate regression model suggested that bacterial community structure in each snail-spring combination was a function of water chemistry and snail relatedness but not physical distance between collection sites. Our data suggested that desert springs harbour not only endemic threatened snail species but also potentially novel bacterial taxa. Bacterial communities driven by host phylogeny and environmental conditions were consistent with literature sources. Bacteria may, in the future, factor in the conservation of desert springs and springsnails in a holistic way.