The resistance of an ecosystem to species invasion is considered to be related to the abundance and diversity of native species. Theory predicts that the high native diversity in pristine systems can hinder the establishment and/or the spread of non-native species through direct and indirect mechanisms.

This study tested whether predation provides higher resistance to invasion by the crab Percnon gibbesi in protected native communities, compared with exploited ones. Predation rate was assessed by manipulative tethering experiments conducted on two size classes of P. gibbesi using long and short tethers, both at protected and unprotected sites.

The obtained results show that the abundance and diversity of the predators of P. gibbesi and the relative predation rate on tethered crabs were higher at protected than at unprotected sites, independent of crab size and tether length. The density of P. gibbesi was significantly lower in protected compared with unprotected sites.

The authors state that these results suggest that the diversity and abundance of native predator assemblages directly affect the invasion success of P. gibbesi in the Mediterranean Sea. It is highlighted that this study provides experimental evidence that the restoration of predator assemblages confers “biotic resistance” to no-take marine protected areas (MPAs) against P. gibbesi invasion.

It is concluded that no-take MPAs are effective in combating non-indigenous species (NIS) invasion, and that it is crucial to establish a long-term monitoring programme to limit the introduction of NIS and to control the spread of existing ones.

Noè et al. (2018) Native predators control the population of an invasive crab in no-take marine protected areas. Aquatic Conservation: Marine and Freshwater Ecosystems 28:1229-1237.