Abstract
The present study constitutes the first evaluation of the space colonization strategies performed by Rugulopteryx okamurae when co-occurring with the resident macroalgal community in the introduced areas. Since the first apparition of the nonindigenous macroalga in the Strait of Gibraltar, its high propagation capacity together with its colonization ability has enhanced the establishment success of the species in detriment of the resident biota. In this study, we carried out observational surveys during 2017–2020 in order to assess the coverage levels of R. okamurae on different lighting conditions, surface orientations, and substrata types (artificial and natural). Results revealed that, beyond the high percent coverages already reported at illuminated and semi-illuminated natural rocky habitats, R. okamurae is able to settle on a wide variety of artificial substrata. The settlement performance of the species was also investigated and different mechanisms underlying the space colonization were proposed. Thus, R. okamurae was observed interacting with 43 resident macroalgal species at generally illuminated rocky habitats of the northern Strait coasts. Six colonization mechanisms were proposed for spatial growth scenarios. Overall, results pointed out that, in most of the cases where the invasive species co-occur with the resident community, R. okamurae would be favored as regards spatial growth success. Competitive interactions and environmental factors which influence results obtained must be addressed in order to fully predict impacts on resident communities. Moreover, together with previous scientific works, overall data provided in this study highlight the need to urgent implement management measures focused on habitats susceptible to be invaded, as well as studies on the ecology and dispersal vectors of R. okamurae in the Strait of Gibraltar and adjacent areas.
Highlights
The introduction and spread of nonindigenous marine species (NIS) are within the major threats to global biodiversity, natural resources, and human health and constitute a priority for the protection and management of coastal areas (Bax et al, 2003; Galil et al, 2018)
In the case of macroalgae, the establishment of the introduced species may lead to competitive interactions with the resident macroalgal community through lateral and epiphytic growth, which can be facilitated by a higher thermal tolerance than its competitors and the production of secondary metabolites for allelopathic defense (Tronholm et al, 2012)
Forty-three macroalgal species were detected in relation to possible implications inferred by the spatial establishment of R. okamurae, including four NIS (A. armata, A. taxiformis, C. cylindracea, and Dictyota cyanoloma)
Summary
The introduction and spread of nonindigenous marine species (NIS) are within the major threats to global biodiversity, natural resources, and human health and constitute a priority for the protection and management of coastal areas (Bax et al, 2003; Galil et al, 2018). When an introduced NIS acclimates and expresses an aggressive ecological behavior, its status progresses from established NIS to invasive NIS. In such cases, NIS competes with the resident community for resources like space, so the ecosystem and its services can be altered. In the case of macroalgae, the establishment of the introduced species may lead to competitive interactions with the resident macroalgal community through lateral and epiphytic growth, which can be facilitated by a higher thermal tolerance than its competitors and the production of secondary metabolites for allelopathic defense (Tronholm et al, 2012). To meet EU regulation on the prevention and management of NIS, it is highly necessary to establish standard methodologies and monitoring plans in sensitive and little-studied areas (Galil et al, 2018)
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