Plastome-based phylogeny and historical biogeography of Erythronium L.

The genus Erythronium L. (Liliaceae) comprises approximately 30 species of spring-flowering perennial herbs that are widely distributed in temperate areas across the Northern Hemisphere. Although species within the genus exhibit considerable morphological similarity, their phylogenetic relationships remain insufficiently resolved. Owing to the limited scope of available datasets and insufficient taxon sampling, previous molecular studies have struggled to fully clarify phylogenetic relationships within the genus. This study presents a plastome-based analysis of phylogeny and historical biogeography in Erythronium, incorporating ten newly sequenced plastomes. All plastomes retained the typical quadripartite structure and presented low overall nucleotide diversity, with infA consistently being pseudogenized across all the taxa. Phylogenetic analyses based on 78 plastid protein-coding genes resolved major infrageneric lineages within Erythronium, corresponding to three well-supported, geographically disjunct clades: Eastern North America, Western North America, and Eurasia. Amana Honda was placed as a strongly supported sister lineage in all analyses. Molecular dating via BEAST estimated that the crown age of Erythronium was 16.7 million years ago (Mya), with subsequent divergences of the Eurasian (8.71 Mya), Eastern North American (5.80 Mya), and Western North American (3.35 Mya) clades occurring after the late Miocene. Ancestral area reconstruction via the BBM indicated East Asia as the most likely origin. The geographically disjunct pattern of Erythronium diversification appears to have resulted from a combination of Miocene-era dispersal via the Bering Land Bridge, global climate cooling, and continental-scale geographic isolation. These results provide new insights into the evolutionary history and biogeographic diversification of Erythronium.