Data for: Comparative biogeography of marine and terrestrial microbes and macrobiota using eDNA

Quantifying how patterns of biodiversity and their underlying processes
vary across diverse environments and ecological communities is a
long-standing challenge in biogeography. The logistics of sampling entire
communities over different geographic scales are barriers to determining
biogeographic theory and conceptual integration at large scales. Here, we
use environmental DNA (eDNA) to overcome these challenges and examine
biogeography hypotheses contrasting diversity in marine versus terrestrial
realms and unicellular versus multicellular organisms. Within two days, we
sampled three habitats (terrestrial, estuarine, marine) along a ~1,400 km
coastal transect in California. We found that eDNA exhibited some novel
and familiar alpha diversity patterns. Marine diversity was lower than
terrestrial diversity in multicellular biota, though statistically
indistinguishable in unicellular biota. Richness was modestly correlated
within habitats and was generally higher in unicellular biota. Beta
diversity was, unexpectedly, less similar within marine than terrestrial
assemblages. Unicellular assemblages were consistently more similar than
multicellular assemblages, and their beta diversity correlated. These
patterns are consistent with predictions based on body size and nuanced
effects of environmental heterogeneity. However, there was considerable
heterogeneity in both datasets. Overall, eDNA provides a common currency
for studying biodiversity patterns and underlying processes (e.g. drift,
migration, selection) across diverse environments and complex communities
and may be the foundation of a unifying macroecological framework.