Contrasting Dispersal Histories Shape Distinct Evolutionary Trajectories Between Malesian and Pantropical Talipariti...

The complex tectonic history of Malesia makes it a critical region for understanding the origins of tropical biodiversity, yet the drivers of plant diversification and range expansion across this region remain poorly resolved. Talipariti (Malvaceae) provides a unique system to test those drivers across Malesia since the Miocene. We aim to test whether species distributions were shaped primarily by stochastic long-distance dispersal (LDD) or by stepping-stone dispersal associated with tectonic collisions, by comparing two Talipariti lineages with contrasting geographic ranges: a pantropical sea hibiscus group and an endemic Papuan group. We constructed a phylogenomic framework using genome-wide nuclear loci and plastome data, estimated divergence times, and applied quantitative biogeographical modelling to compare alternative dispersal scenarios, explicitly testing the contribution of founder-event speciation and incorporating time-stratified palaeogeographical information. Talipariti originated within Malesia ca. 20 Ma. A vicariance event along Lydekker's Line separated the Papuan group to the east from the remaining lineages to the west at ca. 8 Ma, and subsequently, the sea hibiscus group underwent rapid radiation from ca. 1.4 Ma. Biogeographical models reveal a pronounced dichotomy: the sea hibiscus group is best explained by unconstrained models incorporating founder-event speciation, whereas the Papuan group is best supported by time-stratified distance-dependent models without a significant contribution of founder events. Pantropical distributions in the sea hibiscus group arose primarily through effective LDD events, whereas the Papuan group distribution expanded via stepping-stone dispersal associated with Miocene Sunda-Sahul island connectivity. These findings demonstrate that the evolutionary fate of plant lineages is not determined by geological history alone, but by the interaction between geological history and lineage-specific dispersal abilities, revealing Wallace's and Lydekker's Lines as permeable filters rather than absolute barriers. Through biogeographical model comparison, this study provides a quantitative framework for understanding how geological history and dispersal processes jointly shape plant diversification across Malesia.