A recurrent biogeographic pattern is the decay of compositional similarity with increasing geographic distance. In microbial ecology, spatial changes in biodiversity, and in particular distance decay of similarity (DDS), have received growing attention during the past decade. This interest has leaded to overwhelming evidence of aquatic and terrestrial microbial communities’ biogeographic patterns. But, although microbial DDS are similar to those of macroorganisms, most of the studies show that microbial DDS slopes are shallower than those of plant and animal communities. The reasons behind these discrepancies are not clear yet. Here, we argue that severe under-sampling can partly account for such discrepancies and propose the used of dark diversity tools to overcome these limitations. We test this idea by comparing bacteria, archaea and fungi DDS relationships in soils to that of a typical Mediterranean shrubland in Spain.
Results/Conclusions
As expected, we observed the DDS for the three domains of microbial taxa to be flatter compared to that of the scrubland. In contrast, when including dark diversity predictions to the observed microbial taxonomic diversity steepen the microbial DDS patterns. Thus, we account for the differences in spatial turnover between these groups. Our results suggest that the spatial scaling differences between microbial and other macroorganisms diversity such as plants, are not due to fundamental biological differences but to severe under-sampling of microbial communities. We propose the use of dark diversity measurements to complete observed diversity patterns in microbial communities and as a useful tool for a better understanding of biogeographical patterns of species diversity