Phylogenomics and Biogeography of the Eastern Asian–Eastern North American Disjunct Genus Hylodesmum (Fabaceae)

Phylogenomics with dense taxon sampling offers a powerful means to resolve taxonomic and phylogenetic uncertainties. Hylodesmum is a legume genus with an East Asian (EA)–Eastern North American (ENA) disjunct distribution; however, its phylogeny and delimitation from Monarthrocarpus and Verdesmum remain uncertain. Here, we employed plastid genomes, nuclear ribosomal DNA, and 353 low‐copy nuclear genes to reconstruct the phylogeny of all recognized taxa across these genera. Our analyses consistently recover Verdesmum as nested within Hylodesmum , whereas Monarthrocarpus is distantly related. Within Hylodesmum , two major clades were recovered, which are better defined by flower color and leaf margin than by traditional morphological traits. Cytonuclear incongruence in the H. podocarpum and H. laxum complexes suggests likely chloroplast capture. Biogeographic reconstruction supports an “out of Himalaya‐Hengduan Mountains” origin for Hylodesmum , with a late Miocene dispersal to North America ( ca . 7.35 Ma), followed by two back‐dispersals to Asia ( ca . 5.67–4.98 Ma). This study reveals a complex history of bidirectional dispersal, likely facilitated by mammals, in an EA–ENA disjunct genus and provides a new phylogenetic framework for the taxonomic revision of Hylodesmum, recognizing 18 species within two sections.