Gondwanan origin and foremost Miocene diversification explain the paleotropical intercontinental disjunction (PID) in the winged seed clade of Malvaceae

Abstract

Understanding the biogeographic and diversification processes that explain current patterns of diversity in cosmopolitan groups is complex. We aimed to understand the historical biogeography by estimating the ancestral area of origin and diversification of tropical to subtropical plant genus Eriolaena DC. of the subfamily Dombeyoideae (family Malvaceae). To trace the evolutionary trajectory of this clade, fossil leaves exhibiting similarities to the modern genus Eriolaena are described here as E. paleowallichii from the early Paleogene succession of Rajasthan (India). This marks the first fossil record of Eriolaena, commonly known as the Winged Seed Clade (WSC), making this discovery crucial for understanding the evolutionary history of the clade. The Winged Seed Clade (WSC) of the subfamily Dombeyoideae initially included three genera: Eriolaena, Helmiopsis, and Helmiopsiella. However, subsequent taxonomic revisions, based on morphological and molecular studies, led to their consolidation under the genus Eriolaena. This winged clade shows a palaeotropical intercontinental disjunction (PID), mainly located in Southeast Asia, India, and Madagascar with only a single species in Africa. We assembled a dense sampling of the WSC throughout the current geographical distribution to reconstruct the historical biogeography of this clade. A detailed phylogenetic study indicates that the WSC diverged from its sister clade Andringitra in the lower Cretaceous (∼88 Mya, credibility intervals 72.39–105.35), the initial diversification of the WSC occurred around 74.15 Mya (credibility intervals 60.82–88.62 Mya) and broadly this clade was globally diversified in the Miocene. The DEC+J model indicated that (1) WSC likely originated in Madagascar around 79 Mya (2) jump-distance dispersal events were inferred between Madagascar to India and Madagascar to Africa, (3) ‘Out of India dispersals’ occurred mainly in the Miocene, allowing this clade to colonize in Southeast Asia. Biogeography and divergence dating indicate that the Miocene was an important epoch when this clade diversified globally. Our findings suggest that an ancient origin connected with a dispersal history enabled by terrestrial land bridges and long-distance dispersals is likely to explain the winged seed clade's palaeotropical intercontinental disjunction (PID).