Identifications are given for 713 specimens of Hymenophyllaceae collected on Ambon and Seram islands, the Moluccas, Indonesia, during 1983–86. The collection is composed of forty-seven species and one variety belonging to seven genera. The dataset is deposited in GBIF and available at https://www.gbif.jp/ipt/resource?r=seram_hymen.

Ambon, filmy ferns, Hymenophyllaceae, Malesia, pteridophyte flora, Seram

The flora of Seram and Ambon islands, the Moluccas, covering bryophytes, pteridophytes and seed plants, was investigated during field expeditions in 1983, 1984–85 and 1986. As the Moluccan islands, in particular Seram, have been explored very sparsely, the expeditions aimed to make general collections of the land plants in the area. More than 11,000 field numbers of vascular plant and 5,000 bryophyte specimens were collected, mainly from east, central and west Seram (Kato 1990a).

The pteridophyte flora of Seram and Ambon was revised by Kato (1990a), who has continuously contributed to this topic, based on his taxonomic studies in identifying our collections. Kato (1990a) provided an overview of the fern flora of Seram and implied that well over 700 species of pteridophytes occur on the island, based on the collection of nearly 700 species on only three explorations. The collection lists of pteridophytes, excluding Hymenophyllaceae, were already published by M. Kato and his collaborators (Kato 1988, 1989a, 1989b, 1990b, 1992, 1994, 1996, 1997, 2007, Kato and Kramer 1990, Kato and Parris 1992, Kato and Price 1990).

The GBIF dataset is a list of specimens of Hymenophyllaceae collected in Seram and Ambon from 1983 to 1986. The first two sets of specimens of this family are kept in TI and BO; the third more or less incomplete set will be in L, with a few more duplicates to be distributed to other herbaria. In total, 47 species of the Hymenophyllaceae are recorded.

Seram has an area of about 17,000 km² with many mountain peaks reaching 2,000 to 3,000 m elevation, the highest being 3,019 m. When the collections were made in 1980s, most mountainous areas were still natural and undeveloped, covered mostly with primary forests. Mountains over 1500 m elevation are in a cloud zone of mossy forests where filmy ferns prefer to grow. For the species enumerated here, the habitat of each species is summarised and edited from the field notes on the collection labels. There are widespread calcareous areas on Seram Island and most collections are from such areas. Ambon is a much smaller island, located southwest of Seram. The flora of Ambon had been relatively better known than Seram’s because of the epoch-making pre-Linnean work of G. E. Rumphius’ Herbarium Amboinense. However, the island is now well populated and has been deforested. A small number of Hymenophyllaceae were collected on Ambon. On Seram Island, no particular species of filmy fern necessarily grow in limestone areas. For the epiphytic species, calcareous habitats appear to be of less concern. The epipetric species cited in the following list usually grow on very wet, often moss-covered limestone as facultative calcareous species.

We are grateful to our field collaborators who shared the hard work on Ambon and Seram. Cordial thanks are also due to the directors and curators of the herbaria concerned who allowed us to work under good conditions. We are grateful to Dr. David Boufford for his linguistic check and to all those who helped us to complete this paper, to Dr. Osamu Kurashima for his assistance for dataset preparation and to the two reviewers who kindly provided useful comments.