Spatiotemporal Varition of Mesofaunal Communities
Sponges host a diverse array of mesofaunal symbionts including polychaetes, crustaceans, and ophiuroids. Previous spatiotemporal studies of mesofaunal communities have been constrained to a single sampling event or a single location across one year. This study documents the spatiotemporal variation of symbiont communities associated with Tedania ignis in mangroves and seagrass beds across three years.
Invasibility of Mesofaunal Communities
Community composition can be influenced by abiotic factors, biotic interactions, and the regional species pool. To examine the influence of priority effects and an expanded regional species pool on mesofaunal community composition I performed reciprocal transplants of T. ignis between mangroves and seagrass beds in the Florida Keys to test two predictions: 1) that priority effects would prevent colonization by new species unless they occupied a new niche and 2) that species richness would increase following a move between habitats (i.e. moving T. ignis from a seagrass bed to a mangrove) because of an increase in the regional species pool.
Results/Conclusions
Spatiotemporal Variation of Mesofaunal Communities
Symbiont communities are strongly influenced by habitat (PERMANOVA, P=0.001) and year (PERMANOVA, P=0.0001). Some symbionts, such as the polychaete Branchiosyllis oculata, are found in sponges from both habitats. Other symbionts, such as ophiuroids, are found exclusively in sponges from mangroves. Although symbiont communities had similar taxonomic structure across years (e.g. proportion of Polychaeta, Ophiuroidea, Crustacea), there was turnover of species within each taxonomic category.
Invasibility of Mesofaunal Communities
Community turnover can be induced by transplanting, and symbiont community composition is influenced by both the native habitat (PERMANOVA, P<0.001) and the novel habitat (PERMANOVA, P<0.001). Priority effects influenced community turnover as symbionts that were lost from the sponge following the transplant were often replaced by morphologically similar species. An increase in the regional species pool did not increase species richness of mesofaunal communities as predicted; rather, species richness declined when sponges were moved between habitats. This result may be explained by increased mortality of sponges moved between habitats and suggests that there may be subpopulations of T. ignis in the Florida Keys that are locally adapted.