Species diversity and invasibility: no biotic resistance after the arriving of Rapana venosa (Neogastropoda, Muricidae) to the Río de la Plata (35°-36°S)

GIBERTO, D.A.; SCHIARITI, A.; BREMEC, C.S.

Aberdeen

Congreso; World Conference on Marine Biodiversity 2011; 2011

Species diversity may enhance resistance to invasion if more diverse communities monopolize available resources leaving little resource space for new species. On the contrary, if the invader utilizes different resources than local species, then diversity is less important to control invasibility. This work analyzes benthic diversity before and after the invasion of R. venosa (RV) in the Río de la Plata (RLP) in 1999, looking for relationships between species richness and invasibility. A database of 120 benthic sites (1992-1999= before invasion, 2001-2005= post invasion) across a similar salinity gradient were selected for multivariate and univariate analyses. Species richness of pre-invasive (sampler= dredge, grab; n=50; average ± sd=8.98±7.26) and post-invasive (sampler= grab; n=70; 6.80±5.29) sites was similar (ANOVA, F=1.824, p=0.18). Minor differences in species composition were found (ANOSIM test, R= 0.177, p= 0.1%). Differences arose due to dissimilar frequencies of shared species (SIMPER analysis), which determined that sites grouped without a clear pattern in the MDS analysis. RV preys over clams and mussels in the RLP, and the absence of large gastropods suggests that RV took advantage of unexploited resources. Indeed, the maintenance of quite similar benthic assemblages after the invasion also suggests that species diversity was unimportant to its invasion.