Abstract
Meehania montis-koyae Ohwi (Lamiaceae), which has been considered a narrow endemic and endangered species in Japan, was found in eastern China in 2011. China and Japan belong to the same floristic region and share many plant species, but it is very rare that Japanese narrow endemic species are newly found outside of the country. We examined herbarium specimens of both countries, and conducted analyses of molecular phylogenetics, population genetics, and divergence time estimation using two nuclear (ITS and ETS) gene regions and MIG-seq data. Chinese plants tend to become larger than Japanese, and they are different in leaf shape and floral features. Molecular phylogenetic analysis shows Chinese and Japanese M. montis-koyae are the closest relatives to each other. Population genetic analysis indicates no current gene flow between the Chinese and Japanese populations, and divergence time analysis shows they were separated during the late Miocene. We reach the conclusion that Chinese and Japanese M. montis-koyae have already become distinct biological entities, and a new taxon name Meehania zheminensis A. Takano, Pan Li, G.-H.Xia is proposed for the Chinese plants. A key to Asian Meehania species is provided.
Highlights
The Sino-Japanese floristic region is well known for its richness in species and high degree of endemism [1,2]
Chinese plants are larger in size and robust compared to Japanese ones (Figure 1a,b)
The size of the largest leaf in a shoot is significantly larger in Chinese plants than in the Japanese specimens
Summary
The Sino-Japanese floristic region is well known for its richness in species and high degree of endemism [1,2]. The floristic relationships between eastern China and Japan are closer than that between northeastern China and Korea; the similarity indices of genera and species of seed plants in the two regions are 72.6% and 43.3%, respectively [3]. Many plants in eastern China are conspecific with those in Japan, e.g., Cercidiphyllum japonicum Siebold et Zucc. The genus Meehania Britton is a small herbaceous genus in Lamiaceae. It contains less than ten species [4,5]; only one species, M. cordata (Nutt.) Britton, is distributed in eastern North America, and the others in East Asia, showing a typical pattern of Arcto-Tertiary floristic disjunction [6,7,8]
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