History and biogeography of the mangrove ecosystem, based on a critical reassessment of the paleontological record.

The geological record of mangrove plants is based on comparable morphological characteristics of pollen, fruits and wood, of fossil and modern species. But this record relies on the assumption that the ecological and habitat preferences of ancestral taxa have remained similar through ages. A reexamination of fossil evidence of Avicennia, Pelliciera, Sonneratia, Rhizophora, Bruguiera, Ceriops, etc. reveals that the modern mangrove flora was pantropic by the Eocene, and appears to have originated during Paleocene times. Earlier Paleozoic and Mesozoic candidates for a mangrove ecology lack conclusive evidence of their exclusive association with tidal environments. It is therefore clear that continental drift had a limited role in the dispersal and development of modern mangrove floras. The Eocene/Oligocene boundary crisis appears to herald a beginning of the biogeographic split between the current-day eastern and western provinces of mangrove plants. But, while the climatic origins of this major disjunction is not clearly understood, our reassessment of Tertiary paleoclimates suggests that the major cooling events of the middle Paleocene, the end of the Eocene and the middle Pliocene were the most likely influences on the evolution of mangrove floras. The associated invertebrates, especially molluscs, further support our assertion that a modern mangrove ecosystem was established only during the earliest Eocene times. We summarize our interpretation in a set of 9 palinspastic maps of fossil mangrove genera through their evolution ending with the current, bipartite distribution of present day taxa. [ABSTRACT FROM AUTHOR]