Fine-scale spatial patterns in hot springs mat bacterial communities

Some of the most widely recognized spatial scaling relationships in ecology include the species-area, the abundance-occupancy, and the community compositional similarity-geographic distance relationships. These patterns have been shown to emerge from common mechanisms, such as habitat heterogeneity and colonization-extinction dynamics, and are predicted by various ecological models and theories, including Island Biogeography, Metapopulation theory, and Neutral Theory of Biodiversity and Biogeography. These patterns have been studied in microbial communities at large-scale, but studies at fine grain and small extent are rare, despite at a fine-scale, emerging patterns can be tested with a higher resolution. In this study, we explored these macroecological patterns in bacterial communities inhabiting hot springs mats, which have been shown to exhibit fine-scale spatial heterogeneity in fundamental environmental parameters such as temperature. In three different localities, we sampled a grid with a heterogeneous temperature at a fine-scale, a small extent (approximately 150 cm2), and fine grain (each containing 30 cells spaced about 1 or 2 cm apart). Our findings revealed sublinear scaling for the species-area relationship, with similar parameters across localities, indicating a low rate of spatial species turnover. For the abundance-occupancy relationship, we observed increasing trends, meaning that species that occupied more patches were, on average, more abundant. Additionally, we identified a decay in community compositional similarity with distance in two of the localities, though with low parameter values, indicating minimal geographic isolation at this scale. These results are consistent with different models that predict that spatial ecological patterns arise from spatial heterogeneity, as different species can partition their niches in space and constitute an example of predictable spatial patterns at a fine scale.