A new specimen-based checklist of ferns and lycophytes from Rotuma (Fiji)

The island of Rotuma lies about 580 km north of the main archipelago of Fiji, and while politically part of that country, it differs culturally and floristically. It has not typically been included in botanical treatments for Fiji as a whole despite visits from several botanists. Pteridophytes of Rotuma were described by St. John in 1954 based on a visit there in 1938, but little additional information is available since then. Much of the original Rotuman forest has been altered by human activity, but pockets of original vegetation persist and substantial areas of secondary forest currently occur there. In June 2019, the first two authors of this report visited Rotuma to study ferns and lycophytes. We added six native species to the total of 31 found by St. John, and we found three species that have become naturalised since St. John was there. We revise the identification of several of those that he found, based on studying his specimens as well as our own, and we update nomenclature for many others to reflect current taxonomy. We conclude that 37 native and three naturalised pteridophyte species are confirmed for Rotuma, and two others may be present as natives based on unconfirmed reports. We discuss geographic relationships of the pteridophyte flora and note that at least four native species on Rotuma are not known from elsewhere in Fiji, but almost all Rotuman pteridophytes are known from Samoa. We speculate that additional pteridophytes remain to be found on Rotuma, and we note that declining coconut cultivation is leading to increased recovery of secondary forest on the island. Additionally, we confirm that the endemic angiospermCyrtandra rotumaensisH. St.John [Gesneriaceae] persists on Rotuma.

Automated summary

Rotuma Island, located about 580 km north of the main archipelago of Fiji, is politically part of Fiji but has distinct cultural and floristic differences. The island is home to 37 native and 3 naturalised pteridophyte species, with original vegetation pockets and substantial areas of secondary forest still existing despite human activity. There is potential for the discovery of more pteridophyte species on Rotuma, with unique native species not found elsewhere in Fiji.