7700-Year Persistence of an Isolated, Free-Living Coral Assemblage in the Galapagos Islands: A Model for Coral Refugia?

In an eastern-Pacific coral assemblage at Devil’s Crown, Galápagos Islands, Ecuador, two coral species, Psammocora stellata and Cycloseris ( Diaseris ) distorta , form dense populations of unattached colonies on sand and rubble substrata. In the Galápagos, living C . ( D .) distorta is found only at this single site, whereas populations of P. stellata are found throughout the Archipelago. Six cores dating to ~ 7700 yBP showed P. stellata to be dominant throughout the history of this isolated community, but C . ( D .) distorta increased in abundance from ~ 2200 yBP and reached peak abundance between 1471 yBP and the present. The relative frequency of the two coral species may be linked to millennial-scale climatic variability, and this site may represent a refuge for C. ( D .) distorta from unfavorable climatic fluctuations on millennial timescales. Our results demonstrate that some corals can persist in isolated populations for millennia.