Testing geological models of evolution of the I sthmus of P anama in a phylogenetic framework

The emergence and closure of the I sthmus of P anama had regional and global impacts that were rivalled by few other C enozoic geological events. The closure of the C entral A merican S eaway and the rise of the I sthmus had dramatic affects on climate and air and oceanic currents worldwide. Formation of the I sthmus also drove terrestrial biotic interchange, ending the isolation of S outh A merica by permitting the mixing of its biota with that of N orth and C entral A merica. A dated phylogenetic tree of a well‐sampled clade of palms in the tribe T rachycarpeae ( C opernicia , P ritchardia and W ashingtonia ) was used to conduct biogeographical analyses. Examination of the timing of lineage dispersal from N orth into S outh A merica was performed and two contrasting temporal hypotheses of the I sthmus formation were tested: occurrence in the P liocene ( c . 5 Mya to the present) or in the M iocene (prior to c . 5 Mya). C opernicia is inferred to have dispersed through the I sthmus of P anama region into S outh A merica and subsequently into the C aribbean, where it underwent a rapid radiation. Consistent with a geologically older age for the I sthmus than previously understood, our results support recent geological and palaeobiological data that suggest an early O ligocene to early M iocene model of evolution of the I sthmus of P anama. © 2012 The L innean S ociety of L ondon, B otanical J ournal of the L innean S ociety , 2012, •• , ••–••.