Patchiness in assemblages of epiphytic macroalgae on Posidonia coriacea ata hierarchy of spatial scales

Epiphytic algae are important contributors to ecological functions in seagr ass ecosystems, However, little is known about the spatial scales at which epiphytic algae vary. Such information is vital for elucidating processes t hat structure assemblages, and for providing information on variability imp ortant for designing comparative and experimental studies. In this study, w e examined variation in assemblages of epiphytic macroalgae on Posidonia co riacea at a hierarchy of spatial scales. We sampled according to a nested h ierarchical design, with samples separated by distances ranging from centim etres to kilometres. The largest differences were associated with samples s eparated by kilometres. Differences at the scale of hundreds of metres were comparable to differences at the scale of metres, suggesting that patchine ss at the scale of metres was the dominant pattern at scales less than a ki lometre. Patchiness at the scale of metres may have been related to differe nces in shoot density. Patchiness at this scale might be an important featu re of epiphyte assemblages, and should be considered in designs of studies.