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ItemThe bryophyte flora of Lord Howe Island: taxonomy, diversity and biogeography( 2018)Before this study the known Lord Howe Island bryophyte flora (mosses, liverworts and hornworts) totalled 173 species, consisting of 131 mosses, 40 liverworts and 2 hornworts. For this study I conducted one month of field studies on the island, during which I collected more than 650 specimens, and also studied collections from the island held in Australian herbaria and other collections available in overseas herbaria. Fourteen moss, 32 liverwort and 1 hornwort species are newly reported from Lord Howe Island, including one liverwort new to science. A further 2 moss and 2 liverwort varieties are also new to the island. Twenty-eight moss and 11 liverwort species are discounted from the island’s flora, as well as 3 moss varieties and 1 liverwort variety. As a result, the known bryophyte flora now totals 178 species, consisting of 117 moss species (122 taxa), 58 liverwort species (60 taxa) and 3 hornwort species. These totals exclude 5 moss and 2 liverwort species whose taxonomic status or presence on the island is considered uncertain. One liverwort variety, Heteroscyphus echinellus var. echinellus, is new to Australia. Fourteen bryophyte species and one variety are endemic to the island. Spiridens muelleri, previously thought to be the same as S. vieillardii from New Caledonia, is shown to be a separate species endemic to Lord Howe Island. Chiloscyphus howeanus is also shown to be a legitimate species endemic to the island. Cololejeunea elizabethae is described as a new species, also endemic to the island. Trachyloma wattsii, considered to be endemic to Lord Howe Island, is supported by a molecular analysis as a legitimate species most closely allied to T. planifolium. Confusion about the correct identities of the two Ptychomitrium species on the island is resolved through a revision of the genus for Australia. A previously unrecorded morphological character of Atrichum androgynum is described from a study of Lord Howe Island plants, and a molecular analysis shows that South American plants previously ascribed to A. androgynum do not belong to that species. Hypnodendron vitiense is shown to be paraphyletic, but not as circumscribed by Touw (1971). The Lord Howe Island plants appear to belong to a morphologically cryptic species distinct from H. vitiense s.str, and substantial genetic variation within H. vitiense subsp. australe as currently circumscribed suggests that it might include more than one taxon. Other molecular investigations clarify the relationship between Lord Howe Island populations and mainland Australian populations of a number of moss species. An original and novel investigation of the potential modes of transport of bryophyte propagules to and from the island is made, and a hypothesis is formed about the origins of its bryophyte flora and the biogeographic relationships to the Australian land mass and other western Pacific islands, including New Zealand and New Caledonia. The nearest region of the Australian mainland is shown to be the most likely origin of most of the island’s bryoflora, with the injection of propagules into the high-level jet stream by storms the most likely dispersal mechanism. The presence of numerous otherwise tropical species on the island is probably a result of dispersal by tropical cyclones moving into the Pacific from north-eastern Australia. Migratory birds are shown to be another potential vector for bryophyte dispersal to the island.