Invasive, non-indigenous corals in a tropical rocky shore environment: No evidence for generalist predation Thaise S.G. Moreira, Joel C. Creed ⁎ Departamento de Ecologia, Instituto de Biologia Roberto Alcântara Gomes, Universidade do Estado do Rio de Janeiro-UERJ, PHLC Sala 220, Rua São Francisco Xavier 524, 20559–900 Rio de Janeiro, RJ, Brazil abstract article info Article history: Received 5 December 2011 Received in revised form 24 September 2012 Accepted 25 September 2012 Available online 27 October 2012 Keywords: Coral Non-indigenous species Predation Rocky shore Tubastraea The biological invasion of rocky shore communities modifies species composition and the interaction between community elements. Two species, Tubastraea coccinea Lesson, 1829 and Tubastraea tagusensis Wells, 1982 have been identified as non-indigenous and invasive to the tropical rocky shores of southeast Brazil. The aim of the current study was to investigate predator–prey interactions between a guild of native potential generalist predators and the non-indigenous corals using total exclusion and partial cages versus controls on a tropical rocky shore in the southwest Atlantic. Despite generalist predators being present in natural den- sities on the experimental system and substantial settlement occurring during the 2 year study (average den- sity of Tubastraea spp. was 11.29 ind. 240 cm -2 ) no significant differences were found in density or size of corals between treatments. Dominant groups in the accompanying biological community (ABC) were encrusting calcareous and turf algae, the sponge Iotrochota sp. and barnacles but ABC height and biomass and sediment mass did not differ between treatments. Due to transport and invasion of new communities these corals are thought to have escaped from predation despite a diverse suite of native potential generalist predators. Both corals have been shown to possess bioactive chemicals which predatory fish avoid and this would seem to be the mechanism of predator avoidance. The successful invasion by Tubastraea spp. in the southwest Atlantic is at least in part due to highly reduced (or nil) predation compared to the native range. © 2012 Elsevier B.V. All rights reserved. 1. Introduction In benthic marine systems community structure is determined by complex interactions between recruitment, competition, predation and disturbance (Menge and Sutherland, 1987). The biological inva- sion of rocky shore communities modifies species composition and the interaction between community elements. The stony coral Tubastraea (Scleractinia: Dendrophylliidae) is non-indigenous to the Atlantic Ocean and was probably introduced into Brazil in the late 1980s (Castro and Pires, 2001) on oil and gas platforms. Two species, Tubastraea coccinea Lesson, 1829 (original distribution Pacific and Indian Oceans) and Tubastraea tagusensis Wells, 1982 (original distri- bution Eastern Pacific), have been identified as non-indigenous and invasive to the rocky shores of southeast Brazil (Paula and Creed, 2004). These azooxanthellate species have established and have now invaded shallow subtidal rocky shores along 900 km of the southeast Atlantic coast in five distinct regions. Tubastraea spp. have been de- scribed as invasive corals which negatively impinge on endemic spe- cies (Creed, 2006; Ferreira, 2003; Paula and Creed, 2005). Lages et al. (2011) demonstrated that the shallow tropical rocky shore communities of the southwest Atlantic are being severely modified by the range expansion of Tubastraea spp. as space occupy- ing native species are being substituted by Tubastraea spp. There is some evidence that community change is mediated by interspecific competitive interactions between native flora and fauna and the non-indigenous corals (Creed, 2006; Lages et al., 2011). However, pre- dation is also known to be an extremely important biotic interaction as predators can significantly influence the abundance of prey (Connell, 1961; Paine and Schindler, 2002; Peterson, 1982), as well as having a significant indirect influence on other trophic levels by top-down ef- fects such as trophic cascade impinging on other community elements (Mumby et al., 2007; Pace et al., 1999; Pinnegar et al., 2000). Recently Rilov (2009) reviewed predator–prey interactions of ma- rine invaders. Of the 29 relevant studies of 21 exotic marine species he listed only two studies of predator–prey interactions where in- vaders were the prey on benthic hard bottoms: the invasive mussel Brachidontes pharaonis (Fischer P., 1870) was preferred over native food items by the whelk Stramonita haemastoma (Linnaeus, 1767) in the Mediterranean (Rilov et al., 2002) and predation of the invasive tunicate Pyura praeputialis (Heller, 1878) by native sea stars and snails fixed the lower intertidal limit of the invader in Chile (Castilla et al., 2004). Rilov (2009) did not identify a single study where a po- tential prey invader was not significantly predated by a native preda- tor, a fact that may not be surprising as a ‘non-interaction’ may remain undetected (or unpublished). Journal of Experimental Marine Biology and Ecology 438 (2012) 7–13 ⁎ Corresponding author. Tel.: +55 21 23340260; fax: +55 21 23340546. E-mail address: jcreed@uerj.br (J.C. Creed). 0022-0981/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jembe.2012.09.015 Contents lists available at SciVerse ScienceDirect Journal of Experimental Marine Biology and Ecology journal homepage: www.elsevier.com/locate/jembe