title: Is the sword moss (Bryoxiphium) a preglacial Tertiary relict?
abstract: The disjunction of floras between East Asia, Southeast North America, West North America, and Southwest Eurasia has been interpreted in terms of the fragmentation of a once continuous mixed mesophytic forest that occurred throughout the Northern Hemisphere due to the climatic and geological changes during the late Tertiary. The sword moss, Bryoxiphium, exhibits a distribution that strikingly resembles that of the mesophytic forest elements such as Liriodendron and is considered as the only living member of an early Tertiary flora in Iceland. These hypotheses are tested here using molecular dating analyses and ancestral area estimations. The results suggest that the extant range of Bryoxiphium results from the fragmentation of a formerly wider range encompassing North America and Southeast Asia about 10 million years ago. The split of continental ancestral populations is too recent to match with a continental drift scenario but is spatially and temporally remarkably congruent with that observed in Tertiary angiosperm relict species. The timing of the colonization of Iceland from Macaronesian ancestors, about two million years ago, is, however, incompatible with the hypothesis that Bryoxiphium is the only living member of an early Tertiary flora of the island. Alaska was recurrently colonized from East Asia. The ability of Bryoxiphium to overcome large oceanic barriers is further evidenced by its occurrence on remote oceanic archipelagos. In particular, Madeira was colonized twice independently from American and East Asian ancestors, respectively. The striking range disjunction of Bryoxiphium is interpreted in terms of its mating system, as the taxon exhibits a very singular pattern of spatial segregation of the sexes.
authors.affiliation: University of Liege, Institute of Botany, B22 Sart Tilman, Liege, Belgium; cE3c - Centre for Ecology, Evolution and Environmental Changes and Platform for Enhancing Ecological Research & Sustainability, Universidade dos Açores, Angra do Heroísmo, Terceira, Açores, Portugal; Department of Plant Biology, University of La Laguna, Tenerife, Spain. Electronic address: jpatino.llorente@gmail.com.
authors.forename: Jairo
authors.initials: J
authors.lastname: Patiño
authors.affiliation: University of Connecticut, Department of Ecology and Evolutionary Biology, Storrs, CT, USA.
authors.forename: Bernard
authors.initials: B
authors.lastname: Goffinet
authors.affiliation: cE3c, Centre for Ecology, Evolution and Environmental Changes, Universidade de Lisboa, Faculdade de Ciências de Lisboa, Departamento de Biologia Vegetal and Museu Nacional de História Natural e da Ciência, Jardim Botânico, Lisboa, Portugal.
authors.forename: Manuela
authors.initials: M
authors.lastname: Sim-Sim
authors.affiliation: University of Liege, Institute of Botany, B22 Sart Tilman, Liege, Belgium; cE3c - Centre for Ecology, Evolution and Environmental Changes and Platform for Enhancing Ecological Research & Sustainability, Universidade dos Açores, Angra do Heroísmo, Terceira, Açores, Portugal.
authors.forename: Alain
authors.initials: A
authors.lastname: Vanderpoorten
mesh_terms: D000413:Alaska; D019068:Bryopsida / Q000235:genetics*; D005060:Europe; D005202:Asia, Eastern; D007055:Iceland; D019684:Magnoliopsida; D009656:North America; D010802:Phylogeny; D058974:Phylogeography
keywords: Ancestral area estimation; East Asia; Extinction; Iceland; Long-distance dispersal; North America