A biogeographic analysis and review of the far eastern Pacific coral reef region

New information on the presence and relative abundances of 41 reef-building (zooxanthellate) coral species at 11 eastern Pacific and 3 central Pacific localities is examined in a biogeographic analysis and review of the easte rn Pacific coral reef region. The composition and origin of the coral fauna and other reef-associated taxa are assessed in the context of dispersal an d vicariance hypotheses. A minimum variance cluster analysis using coral sp ecies presence-absence classification data at the 14 localities revealed th ree eastern Pacific reef-coral provinces: (1) equatorial - mainland Ecuador to Costa Rica, including the Galapagos and Cocos Islands; (2) northern - m ainland Mexico and the Revillagigedo Islands; (3) island group - eastern Pa cific Malpelo Island and Clipperton Atoll, and central Pacific Hawaiian, Jo hnston and Fanning Islands. Coral species richness is relatively high in th e equatorial (17-26 species per locality) and northern (18-24 species) prov inces, and low at two small offshore island localities (7-10 species). A hi gh proportion (36.6%, 15 species) of eastern Pacific coral species occurs a t only one or two localities; of these, three disappeared following the 198 2-83 ENSO event, three occur as death assemblages at several localities, an d five are endangered with known populations of ten or fewer colonies. Prin cipal component analysis using ordinal relative density data for the 41 spe cies at the 14 localities indicated three main species groupings, i.e., tho se with high, mid, and narrow spatial distributions. These groupings correl ated with species population-dynamic characteristics. These results were co mpared with data for riverine discharges, ocean circulation patterns, shore line habitat characteristics, and regional sea surface temperature data to help clarify the analyses as these measures of environmental variability af fect coral community composition. Local richness was highest at localities with the highest environmental variability. Recent information regarding th e strong affinity between eastern and central Pacific coral faunas, abundan ce of teleplanic larvae in oceanic currents, high genetic similarity of num erous reef-associated species, and appearances of numerous Indo-west Pacifi c species in the east Pacific following ENSO activity, suggest the bridging of the east Pacific filter bridge (formerly east Pacific barrier).