Persistence of Gondwanan woods in Myanmar through the Paleogene
Résumé
Background and Aims: Many plant taxa of the tropical forests of South and Southeast Asia have been proposed to have Gondwanan ancestors. One significant event contributing to this origin is the African-Indian-Southeast Asian Floristic Interchange, with first events occurring during the late Cretaceous-early Eocene, before the onset of land connections between India and Asia. As the timing and mechanisms of these dispersals remain unclear, we aim to better document the dynamics of this interchange. The Burma Terrane of Myanmar, once a separate tectonic block, but now part of Southeast Asia, accreted to India in the early Paleogene, making it an ideal location to study floristic exchanges. Methods: We section and describe ten fossil wood specimens, analyzing their anatomy to determine affinities with extant taxa and their biogeographical history. Key results: We present six taxa from the late middle Eocene and lower Oligocene of Myanmar‒ including new species and a new genus ‒ from the families Fabaceae, Moraceae, Myrtaceae, Meliaceae, and Malvaceae. These findings document an extended Gondwanan distribution and biogeographical history of paleotropical lineages. Conclusions: These taxa likely dispersed during the early Paleogene from Africa to India and Myanmar, forming what we refer to as the Indo-Myanmar Paleogene floristic province. This province, which had Gondwanan affinities, persisted at least until the early Oligocene, time of suggested land connection with Asia, and served as a ‘holding pen’ for the further dispersal of some taxa into Southeast Asia, such as the Dipterocarps. However, other taxa, such as those documented in this study, did not disperse further and eventually disappeared during the Neogene. The mechanisms behind these dispersal barriers and the reasons for the eventual disappearance of these taxa from the region are still to be investigated, and could be related to the late Cenozoic changes in monsoonal climate of South Asia.
| Origine | Fichiers produits par l'(les) auteur(s) |
|---|---|
| Licence |