Neogene reef coral assemblages of the Bocas del Toro region, Panama: the rise of Acropora palmata

Abstract

Temporal patterns are evaluated in Neogene reef coral assemblages from the Bocas del Toro Basin of Panama in order to understand how reef ecosystems respond to long-term environmental change. Analyses are based on a total of 1,702 zooxanthellate coral specimens collected from six coral-bearing units ranging in age from the earliest Late Miocene to the Early Pleistocene: (1) Valiente Formation (12–11 Ma), (2) Fish Hole Member of the Old Bank Formation (5.8–5.6 Ma), (3) La Gruta Member of the Isla Colon Formation (2.2–1.4 Ma), (4) Ground Creek Member of the Isla Colon Formation (2.2–1.4 Ma), (5) Mimitimbi Member of the Urraca Formation (1.2–0.8 Ma), and (6) Hill Point Member of the Urraca Formation (1.2–0.8 Ma). Over 100 coral species occur in the six units, with faunal assemblages ranging from less than 10% extant taxa (Valiente Formation) to over 85% extant taxa (Ground Creek Member). The collections provide new temporal constraints on the emergence of modern Caribbean reefs, with the La Gruta Member containing the earliest occurrence of large monospecific stands of the dominant Caribbean reef coral Acropora palmata, and the Urraca Formation containing the last fossil occurrences of 15 regionally extinct taxa. Canonical correspondence analysis of 41 Late Miocene to Recent reef coral assemblages from the Caribbean region suggests changes in community structure coincident with effective oceanic closure of the Central American Seaway (~3.5 Ma). These changes, including increased Acropora dominance, may have contributed to a protracted period of elevated extinction debt prior to the major peak in regional coral extinctions (~2–1 Ma).