Invasion of a rocky intertidal shore by the tunicate Pyura praeputialis in the Bay of Antofagasta, Chile

Abstract

Invasion by marine nonindigenous species (NIS) is a spread phenomenon. The tunicate Pyura praeputialis shows pronounced disjoint geographical distribution: along thousands of kilometers in wave-swept headlands on the southeastern coast of Australia, from where it appears to have originated, and exclusively along 60 -70 km inside the Bay of Antofagasta, Chile. mtDNA sequences suggested that the species invaded this rocky shore recently. We used field manipulations and juvenile P. praeputialis transplant techniques to test hypotheses regarding the capacity of the tunicate to survive and grow at different sites and tidal heights inside and outside Antofagasta, and its competitive performance for primary space (inside the Bay) against the native mussel Perumytilus purpuratus. We conclude that survival and growth of P. praeputialis showed no significant differences among sites inside and outside the Bay, and suggest that the restrictive distribution of the species in Chile is caused by a specific oceanographic retention mechanism and͞or its brief larval dispersal. We demonstrated that, inside the Bay, P. praeputialis outcompetes Perumytilus from the Mid-Low intertidal, constraining Perumytilus to the Upper MidIntertidal, modifying the local pattern of intertidal zonation. We show that predation on P. praeputialis juveniles by starfish and snails constitutes a regulatory mechanism for the setting of its low intertidal limit. Major ecological impacts caused by NIS invasions to rocky shores by aggressive primary space users may result in negative aspects, but also may contribute to biodiversity enhancement. We call attention to the need for increment manipulations and testing of ecological hypotheses regarding marine NIS.

Predation contributes to invasion resistance of benthic communities against the non-indigenous tunicate Ciona intestinalis

“…Among the main obstacles to settlement and establishment by non-indigenous species are biotic interactions, with predation recognized as the most likely factor limiting invasion success in a number of systems (Harvey et al 2004;Levine et al 2004;Parker and Hay 2005;Rilov 2009). Several studies have demonstrated the efficiency of predators in limiting the abundance or distribution of marine invaders (e.g., Byers 2002a; Hunt and Yamada 2003;Castilla et al 2004;deRivera et al 2005), although this predation pressure may be restricted to specific habitats or communities. However, in all presently studied cases the introduced species were able to invade the natural habitats, and it remains unclear whether native predator assemblages could prevent the establishment of invasive species.…”

Mechanisms of invasion resistance: competition among intertidal mussels promotes establishment of invasive species and displacement of native species

“…In marine systems, invasions of non-native species into resident communities are both contributions and threats to local biodiversity (Carlton 1996, Grosholz 2002, but competitive interactions between marine native and invasive species are poorly understood (but see Castilla et al 2004). The Mediterranean bay mussel Mytilus galloprovincialis is a global invader with established populations in the Americas, Africa, Australasia, and Japan (McDonald et al 1991, Sanjuan et al 1997.…”

Ascidians as models for studying invasion success

“…Once non-indigenous ascidians become established in new Lambert (1998), Carver et al (2003), Blum et al (2007), Caputi et al (2007), Lambert (2007), Harrison (2007, 2010), Zhan et al (2010) (2008) and Dupont et al (2010) environments, they may overgrow and out-compete native species and finally become dominant members of communities Bullard et al 2007a;Aldred and Clare 2014). In some cases, population explosions of invasive ascidians reduce the abundance of other benthic species, resulting in transformation of community structure (Castilla et al 2004;Rius et al 2009). For example, invertebrate species richness in San Francisco Bay was negatively correlated with the abundance of a highly invasive ascidian, C. intestinalis, while other species were excluded or became rare in C. intestinalis-dominated communities (Blum et al 2007).…”

“…Many ecological factors including hydrodynamics (Holloway and Connell 2002), substrate condition (Shenkar et al 2008), predation (Pisut and Pawlik 2002;Rius et al 2014a), and competition (Castilla et al 2004;Rius et al 2014a) can potentially influence the spatial distribution of ascidians. Environmental changes associated with human activities (such as coastal construction, overfishing and aquaculture) and global climate changes (such as global warming and El Niño events) have directly and/or indirectly affected such ecological factors, thus facilitating spread and colonization of invasive ascidians (Lambert 2007).…”