Competition for space in two invasive Indo-Pacific corals - Tubastraea micranthus and Tubastraea coccinea: Laboratory experimentation

The invasive Indo-Pacific coral Tubastraea coccinea (Cnidaria, Scleractinia) dominates western Atlantic artificial reef communities. Tubastraea micranthus, a congener, recently invaded the Gulf of Mexico and threatens to become another strong invasive due to similar growth and population expansion characteristics. It also appears to have strong competitive abilities. We examined active competition for space in both of these invasive species to determine their respective capabilities using three sessile Caribbean marine anthozoans - Ricordea florida (Cnidaria, Corallimorpharia), Epicystis crucifer, and Condylactis gigantea (Cnidaria, Actinaria). Coral polyps from the target coral species were placed in contact with the experimental competitor for 3-28 d. T. micranthus responded with an extracoelenteric digestion response to all three Caribbean competitors and was found to be competitively superior. The corallimorpharian R. florida and the anemone E. crucifer elicited extracoelenteric digestive responses from T. coccinea, while C. gigantea did not. The two corals displayed no aggressive interactions towards each other, implying an immune recognition of each other as “self”. Both coral species exhibited aggressive behaviors towards and dominance over their competitors for space. These are characteristics which most likely facilitated the successful invasion of T. coccinea in the western Atlantic. The scleractinian coral T. micranthus, exhibiting similar characteristics, also has the potential of becoming a successful invasive in the Atlantic.