Dispersal limitations and history explain community composition of metaphyton in desert springs of the Bonneville Basin, Utah: A multiscale analysis

We examined patterns of metaphyton community composition from 150 sites in spring wetlands of the Bonneville Basin across three spatial scales: valleys, wetlands nested in valleys, and habitat types nested in wetlands (springs, channels, and marshes) to determine which scale(s) accounted for the greatest variation in metaphyton community composition. We expected local processes at the habitat scale, especially physicochemical differences between springs and marshes, to account for the majority of variation in local community composition but found that the valley scale accounted for 6.3 times more variation than the habitat scale. We suggest the importance of factors that operate at the valley scale, such as historical events (i.e., the draining of ancient Lake Bonneville) and island effects (dispersal limitations) in determining metaphyton community composition. We emphasize that dispersal limitations among valleys may have an important effect on metaphyton community composition despite the prevailing opinion that algae have exceptional powers of dispersal attributed to the worldwide distribution of some species. We base this assertion on three observations: first, the absence of species in isolated springs compared to springs associated with large complexes; second, 67% of the taxa in the Bonneville Basin occurred in only three or fewer sites; and third, the average Bray‐Curtis similarity between all sites based on all taxa (242) was only 14.1%, which is an unlikely low value if metaphyton taxa can freely disperse between sites. Future studies should incorporate the potential importance of history and dispersal limitations as researchers continue to explore patterns of algal community composition across multiple scales.