Rediscovery of the presumably extinct fairy lantern Thismia kobensis (Thismiaceae) in Hyogo Prefecture, Japan, with discussions on its taxonomy, evolutionary history, and conservation

Abstract

Thismia (commonly known as fairy lanterns) is a genus of strange-looking, elusive, and non-photosynthetic plants. Thismia kobensis was first discovered in Kobe City, Hyogo Prefecture, Japan in 1992, but it was believed to be extinct, given that its type locality was destroyed during the construction of an industrial complex. Here, we have reported the rediscovery of T. kobensis in Sanda City, Hyogo Prefecture, which is located approximately 30 km from the type locality. The new locality of T. kobensis is the northernmost distributional limit of Asian Thismiaceae species. As the original description of the species was based on a single museum specimen that lacked two of the three inner perianth lobes, we have provided an amended description of T. kobensis, highlighting its differences from the morphologically similar species T. huangii. Specifically, our morphological re-examination has revealed that T. kobensis is distinguishable from T. huangii by its short but expanded annulus and many short hairs on each stigma lobe. We have also demonstrated that the genetic distance between these taxa is comparable to that between other closely related species pairs. Finally, we have provided brief notes on the taxonomy, biogeography, evolutionary history, and conservation of T. kobensis and its closely related species, including an enigmatic species T. americana.