Event Abstract

Interactive effects of predation and facilitation during the settlement process of non-indigenous species

  • 1 MARE – Marine and Environmental Sciences Centre, MARE-Madeira, Marine Biology Station of Funchal, Portugal
  • 2 Centre of IMAR of the University of the Azores, Department of Oceanography and Fisheries/UAz, Portugal
  • 3 Smithsonian Environmental Research Center, United States

Predicting community invasibility, species invasiveness or identifying the factors that make places more or less invasible have been one of the most important issues in the study of bioinvasions. Species interactions such as predation/grazing and competition are key factors in limiting the success of established invaders and, together with the invader attributes and environmental context determine the success or the failure of the invasion (Kimbro et al. 2013). However, the effects of native consumers (i.e. predators or herbivores) are weak on some invaders and consumer effects can be similar in native and introduced ranges (Maron and Vilá 2001). In addition, in some habitats native and invasive species suffer similar damage by consumers (Agrawal and Kotanen 2003) or even invasive species can suffer greater consumptions (Parker and Hay 2005). Otherwise, positive interactions are also considered as important drivers of community structure (Bulleri 2009) and, in fact, both positive and negative interactions between native and NIS can determine the ability of communities to resist invasions (Bulleri et al. 2008). In particular, ‘Invasional Meltdown’ hypothesis suggests that an invasive species facilitates one another’s invasion by increasing the likelihood of survival and/or ecological impact, and possibly the magnitude of impact (Simberloff 1999). Although it is recognized that interactions contributing to this mechanism are important, evidences are scarce to confirm that facilitative interactions among introduced species are more frequent or important than hindered ones (Simberloff 2006). Located in the Northeast Atlantic, the offshore Madeira island suffers, however, an intense human activity along its coastal environment (i.e. ship trade, aquaculture production, recreation, transportation). In this context, the number of non-indigenous species (NIS) in Madeiran waters has been increasing in recent years due to ongoing monitoring surveys of harbours and marinas. The arrival and/or expansion of NIS from these already invaded areas (i.e. marinas and ports) to other coastal areas can potentially cause unpredictable changes in the biotic structure and composition of ecological communities of the archipelago. Hence, these high human impacted areas (i.e. recreational harbours) provide an excellent environment to conduct experiments for testing theories to explain the invasion process. This study reports a pilot experiment conducted to evaluate how interactive effects of predation and facilitation will affect to settlement success of NIS. Specifically, we tested the hypothesis that (1) the exclusion of predators will promote NIS settlement, and (2) the presence of NIS will favour the establishment of new NIS settlers. Two orthogonal fixed factors (Facilitation and Predation) were included in the experimental design (n = 5). The factor Facilitation included two different treatments: (F+) bare plate with surrounding NIS ring community 9 month aged; and (F-) bare plate free of NIS. To test for predation, both levels of the factor Facilitation were replicated with and without exclusion cages, i.e.(C) caged vs (U) uncaged. Additionally, one more procedural control treatment was included to control for potential artifact effects of the caging, i.e. (PC) that consisted of a bare plate similar to the F- treatment, but with 3 holes in the exclusion cages (on the top and lateral sides of cages) to allow access to predators. Once assembled, experimental plate units were transferred to Funchal marina, located at the south part of Madeira Island, to be exposed to high levels of NIS propagule pressure for 3 months. At the end of the experiment, abundance, species identity and biogeographical status were examined on plate fouling communites for each experimental plate. Preliminary results indicate NIS diversity differs among treatments and it is lower in those treatments with NIS ring, but only in those plates from caged treatment where predators were excluded. Contrary to predictions, evidences found here would suggest that some ecological interactions between NIS already established and new incoming settlers are hindering their establishment success in absence of predators. Interestingly, the increase in predation pressure would change this pattern by favouring the recruitment of greater number of new NIS. More than a simple explanation, a network of direct and indirect processes seems to be involved in determining the net effect of biological interactions during the NIS settlement in this area.

Acknowledgements

I. Gestoso was supported by a postdoctoral grant in the framework of the 2015 ARDITI Grant Programme Madeira 14-20 (Project 002458/2015/132). P. Ramalhosa was partially funded by the Project Observatório Oceânico da Madeira-OOM(M1420-01-0145-FEDER-000001. J. Canning –Clode was supported by a starting grant in the framwork of the 2014 FCT Investigator Programme (IF/01606/2014). This study was partially supported by the Oceanic Observatory of Madeira (M1420-01-0145-FEDER-000001-Observatório Oceânico da Madeira-OOM).

References

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Keywords: non-indigenous species, fouling communities, Marina, invasion process, Biological interactions

Conference: XIX Iberian Symposium on Marine Biology Studies, Porto, Portugal, 5 Sep - 9 Sep, 2016.

Presentation Type: Oral Presentation

Topic: 2. GLOBAL CHANGES, INVASIVE SPECIES AND CONSERVATION

Citation: Gestoso I, Ramalhosa P, Ferreira L and Canning-Clode J (2016). Interactive effects of predation and facilitation during the settlement process of non-indigenous species. Front. Mar. Sci. Conference Abstract: XIX Iberian Symposium on Marine Biology Studies. doi: 10.3389/conf.FMARS.2016.05.00054

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Received: 30 Apr 2016; Published Online: 02 Sep 2016.

* Correspondence: Dr. Ignacio Gestoso, MARE – Marine and Environmental Sciences Centre, MARE-Madeira, Marine Biology Station of Funchal, Funchal, Madeira Island, 9000-107, Portugal, ignacio.gestoso@uca.es