The origins and evolutionary pathways of East Asian subtropical evergreen broad-leaved forests (EBLFs) have long captivated scientists, offering critical insights into biodiversity patterns and ecosystem resilience.

In a study featured cover story in Journal of Systematics and Evolution, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) and their collaborators synthesized decades of research on the spatiotemporal evolution of East Asian subtropical evergreen broad-leaved forests. They clarified the  when and how of the evolution of EBLFS, highlighting their complex emergence and outlining urgent priorities for their conservation in the face of modern global change.

Emerging no earlier than the Eocene epoch, the EBLFs developed in tandem with the Asian monsoon system, as confirmed by molecular and palaeobotanical evidence. Contrary to being a direct relic of ancient boreotropical flora, which was hindered by a vast arid belt, these forests represent a unique mosaic. They are an assemblage of surviving boreotropical relics, tropical elements, and deciduous broad-leaved forest components.

The review underscores that understanding these forests requires looking beyond their boundaries. The researchers regarded that it is crucial to consider the connections EBLFs with adjacent biomes—such as deciduous broad-leaved forests, tropical rainforests, and alpine forests—to avoid an isolated interpretation. Future studies must investigate widely distributed taxa across these biomes to decipher the roles of colonization versus in situ speciation in shaping the region's rich biodiversity.

While fossil records provide invaluable glimpses into the past, they often suggest earlier evolutionary timelines than molecular dating. The researchers call for a more integrative approach, combining palaeoenvironmental reconstruction, molecular dating, biogeographic analysis, and geological data to build a cohesive evolutionary narrative.

The review points out a critical blind spot: a lack of studies on understory trees, herbaceous plants, and other diverse groups that are essential for a holistic understanding of the ecosystem.

The researchers emphasize that proactive strategies are urgently needed, especially for rare plant species with limited distributions.

Contact

MENG Honghu Ph.D

Xishuangbanna Tropical Botanical Garden, CAS

E-mail: menghonghu@xtbg.ac.cn