Historical migration and taxonomy of the Korean endemic shrub Lespedeza maritima

The warm temperate forests of East Asia host many endemic species, making the region a global hotspot of plant species diversity. On the Korean Peninsula alone, over 350 endemic plant species have been reported. Despite this high level of diversity, the evolutionary divergence and establishment patterns of most Korean endemics are poorly understood.

In their new study published in AoBP, Jin et al. investigate the establishment process of Lespedeza maritima (Fabaceae), a Korean endemic shrub that is primarily distributed in warm temperate forests along the southern and eastern coasts of the Korean Peninsula. It is distinguished from other species within the genus by the shiny and leathery upper surface of the leaflets. Despite the distinctive morphology of this species, it poses complex problems in taxonomy. L. maritima has been proposed as either a hybrid (L. cyrtobotrya × L. maximowiczii) or a synonym of L. thunbergia.

In their study, Jin et al. used microsatellite markers to reveal the genetic diversity and structure of L. maritima. The taxonomic identity of this species is also described with comparison to related species. The genetic diversity and structure of L. maritima suggest that current populations are derived from colonisation away from southern refugia after the last glacial maximum (LGM). Ecological niche modelling supports this, showing that L. maritima occurred around the East China Sea and Korean Strait land bridge during the LGM.

Compared with other Lespedeza species, molecular analyses (principal coordinate analysis, neighbour joining analysis and Bayesian tree analysis) and morphological examination indicate that L. maritima is a distinct species and L. uekii should be regarded as synonym. This study could help to improve our understanding about evolution of Korean endemic species.