Format: ORAL

Cheng-Wei Chen1,2, Katsuhiro Yoneoka3, Tao Fujiwara4, Atsushi Ebihara4, Van Truong Do5, Noriaki Murakami3, Yi-Shan Chao2, Yao-Moan Huang6, Ko-Hsuan Chen1, Kuo-Fang Chung1

1 Academia Sinica, Taipei, Taiwan 2 National Taiwan Normal University, Taipei, Taiwan 3 Tokyo Metropolitan University, Tokyo, Japan 4 National Museum of Nature and Science, Ibaraki, Japan 5 Vietnam National Museum of Nature, Hanoi, Vietnam 6 Taiwan Forestry Research Institute, Taipei, Taiwan

In the 1960s, two papers published in the journal Science fundamentally altered our understanding of fern gametophytes, giving the concept of independent gametophyte a prominent place in the field of pteridology. Ferns and lycophytes (pteridophytes) stand out among land plants by having two independent phases in their life cycles: gametophytes and sporophytes. Independent gametophytes refer to those long-lived gametophytic populations that extend beyond the geographic distribution of their sporophyte counterparts. Unlike typical cordiform (heart-shaped) gametophytes, independent gametophytes are non-cordiform and some of them can reproduce asexually through gemmae. In this study, we propose to investigate the origin of the independent gametophyte in a rare species Haplopteris yakushimensis utilizing an integrated approach including molecular biology, reproductive biology, and ecology. Genetic data reveal that the species comprises two diverged lineages (hereafter and ) but their sporophytes are morphologically indistinguishable. The distribution of these two lineages is asymmetric, with the lineage being endemic to Japan, while the lineage is found in Japan, Taiwan, and Vietnam but persisting solely as independent gametophytes in Japan. This system, featuring two sister lineages with distinct reproductive behaviors (i.e., with and without independent gametophytes), offers a unique opportunity to explore the origins of independent gametophytes. Our preliminary data suggest a complex origin of Haplopteris yakushimensis, involving multiple hybridization and polyploidization events. Additionally, both environmental and genetic factors may play roles in shaping the current distribution of the independent gametophytes. Our study is poised to be the most comprehensive in the field and is expected to significantly advance our understanding of gametophyte ecology in general. Furthermore, it will also contribute to the conservation of Haplopteris yakushimensis.