Spatial and temporal variation of coastal mainland vs. insular amphipod assemblages on Posidonia oceanica meadows

Abstract

The vagile fauna associated with Posidonia oceanica meadows is well studied due to the paramount importance of this Mediterranean habitat, but amphipod assemblages show a paucity of information despite the fact they form a relevant component of seagrass systems and associated food webs. This study analyzed the variability of amphipod assemblages in P. oceanica meadows from mainland vs. insular coastal areas in the central Tyrrhenian Sea during two consecutive summer seasons. Our results showed different spatial and temporal patterns of amphipod assemblages from mainland vs. insular coastal meadows, with the latter characterized by a significant variability across time with respect to the more steady composition shown by the mainland sites. Spatial and temporal heterogeneity is due to fluctuating abundances of a small number of species. Complex mechanisms seem to be involved in generating such heterogeneity, including differences in habitat features, factors related to natural demographic oscillations and co-occurring niche- and dispersal-based processes.