title: Not only in the temperate zone: independent gametophytes of two vittarioid ferns (Pteridaceae, Polypodiales) in East Asian subtropics.
abstract: Independent gametophyte ferns are unique among vascular plants because they are sporophyteless and reproduce asexually to maintain their populations in the gametophyte generation. Such ferns had been primarily discovered in temperate zone, and usually hypothesized with (sub)tropical origins and subsequent extinction of sporophyte due to climate change during glaciations. Presumably, independent fern gametophytes are unlikely to be distributed in tropics and subtropics because of relatively stable climates which are less affected by glaciations. Nonetheless, the current study presents cases of two independent gametophyte fern species in subtropic East Asia. In this study, we applied plastid DNA sequences (trnL-L-F and matK + ndhF + chlL datasets) and comprehensive sampling (~80%) of congeneric species for molecular identification and divergence time estimation of these independent fern gametophytes. The two independent gametophyte ferns were found belonging to genus Haplopteris (vittarioids, Pteridaceae) and no genetic identical sporophyte species in East Asia. For one species, divergence times between its populations imply recent oversea dispersal(s) by spores occurred during Pleistocene. By examining their ex situ and in situ fertility, prezygotic sterility was found in these two Haplopteris, in which gametangia were not or very seldom observed, and this prezygotic sterility might attribute to their lacks of functional sporophytes. Our field observation and survey on their habitats suggest microhabitat conditions might attribute to this prezygotic sterility. These findings point to consideration of whether recent climate change during the Pleistocene glaciation resulted in ecophysiological maladaptation of non-temperate independent gametophyte ferns. In addition, we provided a new definition to classify fern gametophyte independences at the population level. We expect that continued investigations into tropical and subtropical fern gametophyte floras will further illustrate the biogeographic significance of non-temperate fern gametophyte independence.
authors.affiliation: Institute of Ecology and Evolutionary Biology, National Taiwan University, Taipei, 10617, Taiwan, Republic of China.
authors.forename: Li-Yaung
authors.identifier: http://orcid.org/0000-0002-3388-3757
authors.initials: LY
authors.lastname: Kuo
authors.affiliation: Division of Silviculture, Taiwan Forestry Research Institute, Taipei, 10066, Taiwan, Republic of China.
authors.forename: Cheng-Wei
authors.initials: CW
authors.lastname: Chen
authors.affiliation: Faculty of Education, Kagawa University, Saiwaicho 1-1, Takamatsu, Kagawa, 760-8522, Japan.
authors.forename: Wataru
authors.initials: W
authors.lastname: Shinohara
authors.affiliation: Department of Botany, National Museum of Nature and Science, Amakubo 4-1-1, Tsukuba, Ibaraki, 305-0005, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Ebihara
authors.affiliation: Center for Ecological Research, Kyoto University, Hirano 2-509-3, Otsu, Shiga, 520-2113, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kudoh
authors.affiliation: Center for Ecological Research, Kyoto University, Hirano 2-509-3, Otsu, Shiga, 520-2113, Japan.
authors.forename: Hirotoshi
authors.initials: H
authors.lastname: Sato
authors.affiliation: Division of Silviculture, Taiwan Forestry Research Institute, Taipei, 10066, Taiwan, Republic of China. huangym@tfri.gov.tw.
authors.forename: Yao-Moan
authors.initials: YM
authors.lastname: Huang
authors.affiliation: Division of Botanical Garden, Taiwan Forestry Research Institute, Taipei, 10066, Taiwan, Republic of China. chiouwl@gmail.com.|Dr. Cecilia Koo Botanic Conservation Center, Pingtung County, 906, Taiwan, Republic of China. chiouwl@gmail.com.
authors.forename: Wen-Liang
authors.initials: WL
authors.lastname: Chiou
mesh_terms: D018744:DNA, Plant / Q000235:genetics* / Q000378:metabolism; D055993:Germ Cells, Plant / Q000502:physiology; D007564:Japan; D018087:Plastids / Q000235:genetics* / Q000378:metabolism; D029625:Pteridaceae / Q000235:genetics / Q000502:physiology*; D017422:Sequence Analysis, DNA; D013624:Taiwan
chemical_list: D018744:DNA, Plant
keywords: East Asia; Fern; Haplopteris; Independent gametophyte; Subtropics; Vittarioid