Stasis or kinesis? Hidden dynamics of a rocky intertidal macrophyte mosaic revealed by a spatially explicit approach

At wave-exposed sites, surfgrass overgrew all other species except the kelp Lessoniopsis littoralis, which was competitively equivalent to surfgrass. Grazing had no effect on spatial interactions. Disturbance prevented surfgrass monocultures, and with variable dispersal and patchy recruitment, maintained mosaic structure. At wave-protected sites, standoffs were the usual outcome of interactions, and patchiness resulted primarily from colonization of disturbances and subsequent succession. Like mussels, Phyllospadix are simultaneously dominant competitors, the most disturbance-susceptible species, and poor colonizers. These features are shared by theoretical models exploring the processes underlying spatially structured assemblages, and may characterize spatially structured systems in general.