Oreohelix strigosa (Rocky Mountainsnail) is a land snail found in the talus slopes of the Rocky Mountains. The University of Colorado’s Museum of Natural History has densely sampled Oreohelix for the past century; many are preserved in ethanol and available for molecular research. While microbiome compositions in other systems are not affected by short-term field season preservation, the effects of decades-long preservation have yet to be assessed. We used 16S rRNA gene amplicon sequencing to examine Oreohelix strigosa gut microbiomes from museum specimens across a 98-year range, as well as within short term preservation treatments collected in 2018. Treatment groups included samples extracted fresh, without preservation; samples starved prior to extraction; and samples preserved for 1 month, 6 months, and 9 months. General microbiome composition was similar across all years. Sample groups belonging to specific years, or specific short-term treatments, showed unique associations with select bacterial taxa. Collection year was not a significant predictor of microbial richness, though unpreserved short-term treatments showed significantly higher richness than preserved treatments. While year was a significant factor in microbiome composition, it did not explain much of the variation across samples. Other factors like location collected and drought index were also significant drivers of community composition and explained as much or more of the variability. This study is the first to examine animal host associated microbiome change across a period of nearly one century. Consistent patterns across this temporal range indicate that historic specimens can answer many ecological questions surrounding the host associated microbiome.

Generalists are thought to adapt to a broader breadth of ecological conditions compared to less flexible specialists. However, few studies have systematically tested what ecological or life-history traits are associated with organisms' ecological flexibility. Here, we used stony corals to test the relative effects of host traits and ecological factors on corals' flexibility to form photosymbioses with algae. We analyzed data from 211 stony coral species to test if coral's geographic distribution, depth range, symbiont transmission mode, or colony morphology predict coral-algal flexibility. We report a novel positive correlation between coral-algal flexibility and coral species' geographic range. Symbiont transmission mode is also a predictor of flexibility, albeit the result is less robust against sampling bias. Coral depth range and morphology did not show significant effects. We discuss how host-symbiont dispersal abilities, interactions, and evolutionary history could contribute to the observed patterns and how this finding could inform conservation efforts.

Animal gut microbiome is often a key requirement for host nutrition, digestion, and immunity. Gut microbiomes can shift in relation to host geography and environmental factors. However, ecological drivers of microbiome community assembly across large geographic ranges have rarely been examined in invertebrates. Oreohelix strigosa (Rocky Mountainsnail) is a widespread land snail ranging across the mountainous western United States. O. strigosa is found in a variety of environments, including dry Southwestern habitats and the near-alpine of the Rocky Mountains. It is ideally suited for biogeography studies due to its broad distribution, low migration, and low likelihood of passive transport via other animals. This study aims to uncover large-scale geographic shifts in the composition of O. strigosa gut microbiomes by utilizing samples from across its native range. Additionally, we elucidate smaller-scale microbiome variation using samples collected only across the Colorado Front Range. Our results show that O. strigosa gut microbiome is variable across the broad geographic range. Within Coloradan samples, we investigated several possible ecological drivers of the geographic variation, including soil and vegetation composition, habitat complexity, habitat type, and human impact. We conclude that several small-scale environmental factors may be driving the changes in O. strigosa gut microbiome composition seen across large-scale geography. Uncovering large-scale shifts in the gut microbiome compositions will help form fundamental questions about the functional aspect of these qualitative changes. This knowledge will also help us better understand how microbial associations influence species survival in diverse environments and aid wildlife conservation efforts.