Date : March 16, 2026
Guangzhou, China : Hylodesmum , a legume genus with a typical East Asian (EA)–Eastern North American (ENA) disjunct distribution, has long been mired in taxonomic uncertainties and ambiguous phylogenetic relationships with allied genera. In a comprehensive study published in Biological Diversity , research by Dr. Zhuqiu Song and Prof. Shijin Li from South China Botanical Garden, Chinese Academy of Sciences, resolves these long-standing questions using an integrated genomic approach.
The study combined plastid genomes, nuclear ribosomal DNA, and 353 low-copy nuclear genes to reconstruct the phylogeny of all recognized taxa of Hylodesmum and its relatives, Monarthrocarpus and Verdesmum . Dense taxon sampling (185 individuals across 24 genera and 63 species) and multi-locus analyses consistently confirmed Verdesmum as nested within Hylodesmum — justifying its synonymization — while Monarthrocarpus was found to be distantly related, warranting its retention as a separate genus.
Morphological and molecular evidence redefined two major clades within Hylodesmum , better characterized by flower color and leaf margin than by traditional traits, leading to a revised infrageneric system recognizing 18 species in two sections. Biogeographic reconstruction supported an "out of the Himalayas–Hengduan Mountains" origin for the genus, with a Late Miocene dispersal to North America (ca. 7.35 Ma) followed by two independent back-dispersals to Asia (ca. 5.67–4.98 Ma), uncovering a complex bidirectional dispersal pattern likely facilitated by mammal-mediated epizoochory.
Cytonuclear incongruence in the H. podocarpum and H. laxum complexes was attributed to chloroplast capture via hybridization, providing new insights into the taxonomic delimitation of these species complexes, with four subspecies elevated to species rank.
This study builds a robust phylogenetic framework for the taxonomic revision of Hylodesmum and elucidates the formation of its EA–ENA disjunct distribution, highlighting the pivotal role of the Himalayas–Hengduan Mountains as a biodiversity source and the impact of Asian monsoon intensification on the genus' diversification.
Image Caption : Integrating data from plastid genomes, nrDNA, and 353 low-copy nuclear genes, this study establishes a robust phylogenetic framework for Hylodesmum . This framework supports a taxonomic revision recognizing 18 species and reveals a complex pattern of bidirectional EA–ENA dispersal, with mammals as a plausible dispersal agent.
Image Credit : Zhuqiu Song, Gang Yao, Chen Ren, Kaiwen Jiang, Dongxian Xu, and Shijin Li
Original Source :
Song, Zhuqiu, Gang Yao, Chen Ren, Kaiwen Jiang, Dongxian Xu, and Shijin Li. 2026. "Phylogenomics and Biogeography of the Eastern Asian–Eastern North American Disjunct Genus Hylodesmum (Fabaceae)," Biological Diversity : 1 - 19.
https://onlinelibrary.wiley.com/doi/10.1002/bod2.70020
Keywords : disjunct distribution, Himalaya, legumes, phylogenomics, Verdesmum
About the Author :
Zhuqiu Song: South China Botanical Garden, Chinese Academy of Sciences, specializes in plant taxonomy and phenology.
Dongxian Xu (Correspondence) : Guangdong Academy of Forestry, has long been committed to the research and practice of plant taxonomy and ecological restoration of difficult habitats.
Shijin Li ( Correspondence ) : South China Botanical Garden, Chinese Academy of Sciences, engages in the taxonomy of Fabaceae and the accurate identification of precious rosewood.
About the Journal :
Biological Diversity (ISSN: 2994-4139) is a new open-access, high-impact, English-language journal devoted to advancing biodiversity conservation, enhancing ecosystem services, and promoting the sustainable use of resources under global change. It features innovative research addressing the global biodiversity crisis.
Biological Diversity
Experimental study
Not applicable
Phylogenomics and Biogeography of the Eastern Asian–Eastern North American Disjunct Genus Hylodesmum (Fabaceae)
10-Mar-2026
Conflicts of Interest The authors declare no conflicts of interest. Ethics Statement The authors have nothing to report.