Oligocene Revolution

The Eocene Pelliciera mangroves were replaced by different mangrove communities dominated by Rhizophora, the precursors of modern mangroves, during the Eocene–Oligocene transition (EOT). The EO (T33.8–33.5 Ma) was characterized by relevant global tectonic and climatic disruptions that greatly influenced biotic patterns worldwide. In the Caribbean region, the EOT disruption was manifested in an abrupt cooling (3–6 °C) and sea-level fall (67 m), coinciding with a shift in mangrove dominance from the autochthonous Pelliciera to the allochthonous Rhizophora, originating in the IWP and arriving by long-distance dispersal in the Late Eocene. Pelliciera remained as a subordinate mangrove element and was restricted to a small equatorial patch around the Panama Isthmus, where it still thrives. It is proposed that the EOT cooling and sea-level fall could have favored the expansion of the eurythermic and vagile Rhizophora, which outcompeted the stenothermic Pelliciera, of limited dispersal ability. The survival of Pelliciera could have been facilitated by Rhizophora, which would have provided shelter against environmental stressors, such as light intensity and salinity. In this way, competence would have turned into facilitation, thus promoting coexistence by niche segregation. In this trade, Pelliciera could be viewed as an ecological looser, by losing its dominance, but an evolutionary winner, by surviving under generally unfavorable conditions.