2024 Volume 75 Issue 2 Pages 71-83
In the oceanic Bonin Islands, both the flora and fauna exhibit adaptive radiation and ecological differentiation. Elaeocarpus photiniifolia Hook. & Arn. (Elaeocarpaceae), a tree endemic in the Bonin Islands, grows in a wide range of environments, from dry scrub to mesic forests. In the Chichijima Islands, we observed genetic differentiation between the shrub ecotype in dry scrub and the tree ecotype in mesic forests. Conversely, on Hahajima Island, only one genetic group was known in mesic forests. Recent surveys, however, revealed a small number of individuals of E. photiniifolia in the dry scrub of the Hahajima Islands. This study aimed to determine whether genetic differentiation corresponding to vegetation types also occurs in the Hahajima Islands. To investigate this, we used 17 EST-SSR markers for genotyping to determine the genetic attributes of individuals in the dry scrub of the Hahajima Islands. Our data revealed that individuals from the dry scrub were highly differentiated genetically from the known genetic group of Hahajima Island that occurs in mesic forests. Additionally, we observed that individuals in the dry scrub flowered earlier than those in mesic forests. Our findings indicate that E. photiniifolia is both genetically and ecologically differentiated in the Hahajima Islands, with the dry scrub populations likely having originated from a secondary migration of shrub ecotypes from the Chichijima Islands, possibly facilitated by infrequent seed dispersal across island groups.
