For decades, scientists have debated whether Hainan Island, China’s largest tropical continental shelf island, underwent significant tectonic displacement during the Cenozoic era and whether such movement shaped its unique biota.
In a study published in Journal of Biogeography, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) provided a comprehensive rebuttal to the "Hainan drift" hypothesis, concluding that the island’s biogeographic evolution was likely driven by periodic land bridges rather than tectonic displacement.
Situated in the South China Sea and separated from the mainland by the Qiongzhou Strait, Hainan Island has long served as a natural laboratory for studying biogeographic links between continental blocks. Since the 1950s, two central questions have fueled debate: Did Hainan Island drift southward from the Beibu Gulf (Gulf of Tonkin) during the Cenozoic? If so, did this displacement directly influence the evolution of its flora and fauna? Early paleomagnetic studies and simplified geological models suggested possible displacement, but conflicting evidence from geology, geophysics, and biology left the issue unresolved.
The researchers systematically evaluated geological, paleomagnetic, and biological data to address these questions. Their study found no conclusive evidence supporting large-scale Cenozoic displacement of Hainan Island.
“The hypothesis of Hainan’s drift has largely relied on oversimplified models and unverified assumptions,” said Dr. Meng Honghu, co-corresponding author of the study. “Our multidisciplinary analysis shows that periodic land bridges, not tectonic displacement, were the primary drivers of biotic exchange.”
The study emphasizes that repeated exposure of the Beibu Gulf seabed during glacial periods created migration corridors, allowing frequent species exchanges between Hainan, the mainland, and Indochina. While some phylogenetic patterns might suggest historical isolation, the team argues that long-distance dispersal and cyclical land connections sufficiently explain biogeographic affinities.
Contact
MENG Honghu Ph.D
Xishuangbanna Tropical Botanical Garden, the Chinese Academy of Sciences
E-mail: menghonghu@xtbg.ac.cn
First published: 20 May 2025
