Can invasive habitat-forming species play the same role as native ones? The case of the exotic marine macroalga Rugulopteryx okamurae in the Strait of Gibraltar.

Navarro-Barranco, C.; Muñoz-Gómez, B.; Saiz, D.; Ros, M.; Guerra-García, J. M.; Altamirano, M.; Ostalé-Valriberas, E.; Moreira, J.

The addition or loss of habitat-forming species may lead to significant changes in the structure and functioning of marine benthic ecosystems as a whole. However, the nature of the impact of invasive macroalgae on native mobile invertebrate assemblage is still hard to predict. In this sense, the degree of morphological resemblance (mainly structural complexity) between native and exotic habitat-forming species has been proposed as a suitable predictor of epifauna response to biological invasions. The recently introduced macroalga Rugulopteryx okamurae is becoming a dominant element in coastal rocky bottoms in the Strait of Gibraltar, where it is sympatric with the native species Dictyota dichotoma. Despite the high morphological similarity between both habitat-forming species, native and exotic macroalgae hosted different macrofaunal assemblages. Dictyota dichotoma showed lower number of species, abundance of individuals, and diversity values than the introduced macroalga. Most shared species showed higher abundance on R. okamurae, but there was high variability in the response to macroalgal identity across higher taxa. Thus, there were no major differences in polychaete assemblage between macroalgal species or among sites, when considering univariate measures (abundance of individuals, number of species and H′ values) or species composition (with the exception of abundance values), while peracarid crustaceans and molluscs showed the opposite pattern. Therefore, our results suggest that morphological similarities among habitat-forming species do not always allow predicting of whether the invasive taxa are functionally equivalent to native ones. They also highlight the relevance of fine taxonomical resolution for revealing complex impacts of invasive macroalgae. In addition, R. okamurae's capacity to determine significant changes on native fauna has been pointed out.

BIOLOGICAL invasions; INTRODUCED species; ALGAL communities; POLYCHAETA; STRAITS; OFFSHORE structures; NATIVE animals; MARINE ecology

Biological Invasions, 2019, Vol 21, Issue 11, p3319

1387-3547

Academic Journal

10.1007/s10530-019-02049-y