Conservation units and the origin of planted individuals of an endangered endemic species Lobelia boninensis in the Ogasawara Islands

Abstract

The Ogasawara Islands, one of the UNESCO World Natural Heritage Site located about 1000 km south of Japan's main island, harbor numerous endemic species, many of which are as endangered. One of the endemic plant species, Lobelia boninensis, found in the Mukojima, Chichijima, and Hahajima archipelagoes, is endangered due to predation. As part of conservation efforts, translocation is now underway, especially on Chichijima. However, we lack essential information, such as the genetic population structure, to develop appropriate translocation strategies for both wild and planted individuals. Here, we aimed to identify the conservation units and the origin of planted individuals by estimating the genetic population structure and phylogenetic relationships across all habitats of this species. We identified two distinct genetic clusters, indicating genetic differentiation between the northern and southern populations. The genetic population components detected at an isolated site on Chichijima showed a mixture of these distinct clusters, probably due to hybridization. The transplanted individuals in Chichijima were found to have originated from a population in Hahajima. These results suggest the presence of two distinct conservation units. Furthermore, the current translocation strategy poses a risk of genetic contamination between these units, highlighting the need for revised conservation management practices.