11th International Temperate Reefs Symposium (ITRS) 2016, University of Pisa, Italy
Alfonso Siciliano, Mads S. Thomsen, David R. Schiel
It is well established that host species that are morphologically and genetically different can support different epibiotic species, and that these differences can support different invertebrate communities. However, no studies have tested the opposite hypothesis of whether morphologically similar congeneric hosts support similar epibiota and have similar cascading effects on invertebrate communities. This hypothesis was tested with mensurative and manipulative experiments using three conspecific, morphologically similar marine seaweed hosts: the canopy-forming fucoids Cystophora torulosa, C. scalaris, and C. retroflexa. In the mensurative experiment, hosts, epiphytes and associated invertebrate communities were sampled and enumerated from 4 tide-pools (>1 m apart), at 2 reefs (>1 km apart) and 4 sites (>100 km apart). In two follow-up manipulative experiments, defaunated hosts, epiphytes and epiphytes’ mimics were combined and transplanted to shared tide pools and the epifaunal recolonization was quantified. Both experiments suggest that epiphytism increases abundances and richness of invertebrates, across host species, epiphyte species, sites, regions, and experimental methods, demonstrating its key role in sustaining the epifaunal community. However, the experiments reject the initial hypothesis since congeneric and morphologically similar hosts appear to support a different epifauna and having different cascading effects.