Effects of competition between two introduced Caulerpa

Abstract

Competitive interactions between 2 introduced algae, Caulerpa taxifolia and C. racemosa, were studied in 2 experiments. The first separately evaluated the interspecific and intraspecific effects on both species by manipulating their abundance. The second investigated the fate of fragments of C. taxifolia transplanted into patches of C. racemosa, in contrast to those established on algal turfs. C. racemosa and C. taxifolia had similar temporal trends in growth but reached different sizes. The overall increase in stolon length at higher densities for both species suggested that positive interactions are very important. However, there was a significant interspecific effect on C. taxifolia stolon length but no effect on C. racemosa. Furthermore, C. taxifolia fragments transplanted into C. racemosa patches showed clear signs of stress with respect to those transplanted into algal turfs: blades became blanched and eroded. Overall, the results of this study suggest that growth increases with density augmentation, therefore suggesting that invasive characteristics of the species may increase with the time of colonisation. Both species tend to spread faster at higher density. Overall, where both species co-occur, we predict that C. racemosa would be the favoured species as regards the outcome of competition.

A Comparison Among Assemblages in Areas Invaded byCaulerpa taxifoliaandC. racemosaon a Subtidal Mediterranean Rocky Bottom

“…Spreading characteristics of co‐occurring populations have been compared and interactions between the two species have been evaluated in previous studies (Piazzi et al. , 2001a; Piazzi & Ceccherelli, 2002).…”

Taxonomic diversity and geographic distributions of aquarium-traded species of Caulerpa (Chlorophyta: Caulerpaceae) in southern California, USA

“…For example, 3 C. racemosa varieties have been identified in the Mediterranean Sea using both morphological (Verlaque et al 2000) and genetic (Durand et al 2002) criteria. Because these varieties are difficult to distinguish on morphological grounds alone, most of the published literature on C. racemosa invasions in the Mediterranean Sea (Verlaque 1994, Ceccherelli et al 2000, Piazzi et al 2001, Ceccherelli & Campo 2002, Piazzi & Ceccherelli 2002 fails to identify the invasive variety, 101 0°1 5°N 30°N 45°N 60°N 15°S 30°S 45°S 0°15°W 60°W 90°W 120°W 150°W 180°30°E 6 0°E 9 0°E 1 2 0°E 1 5 0°E 0°15°W 60°W 90°W 120°W 150°W 180°30°E 6 0°E 9 0°E 1 2 0°E 1 5 0°E…”

Impacts of Marine and Lagoon Aquaculture on Macrophytes in Mediterranean Benthic Ecosystems

“…In fact, a large number of introduced species can coexist in the same ecosystem, as occurs in e.g., coastal lagoons, along the Tuscany coast (Italy) and in the eastern Mediterranean basin (Piazzi and Cinelli, 2003;Piazzi and Balata, 2009;Boudouresque et al, 2011). Introduced species can of course compete with each other (Piazzi and Ceccherelli, 2002). Thau Lagoon illustrates the disruption of the ecosystems and seascapes by a host of introduced macroalgae, which may outnumber the native species, and represent the bulk of the biomass of primary producers in some habitats.…”