Miocene Syzygium Gaertn. (Myrtaceae) from India and its ancestral lineages from Gondwanaland

Abstract

Syzygium is the largest woody angiosperm genus, widely distributed across tropical and subtropical regions in the Old World. Despite its ecological prominence, its fossil record remains underexplored, leading to ongoing debates about its origin and biogeographic history. This study reports eleven newly discovered Syzygium fossil leaves from the Early Miocene Kasauli Formation of Himachal Pradesh, India. Based on morphological and cluster analysis of 156 plant species across 21 extant angiosperm families, utilizing 22 leaf morphological characters with 79 different character states, we identified the fossil as a new species, Syzygium paleosalicifolium sp. nov. Additionally, we reinvestigated previously reported Syzygium fossils from the Paleogene and Neogene sediments of India to refine evolutionary timeline of the genus. Our findings confirmed the presence of Syzygium in India since at least the early Eocene, challenging hypotheses of an exclusively Australian or Southeast Asian origin. The Indian fossil record supports an East Gondwanan lineage, predating the proposed Miocene origin and diversification of the genus. Furthermore, our results suggest that Syzygium may have diversified earlier than the ∼51.2 Ma crown age estimated by molecular phylogenetic studies.