Abstract
Molecular data from three chloroplast markers resolve individuals attributable to Radula buccinifera in six lineages belonging to two subgenera, indicating the species is polyphyletic as currently circumscribed. All lineages are morphologically diagnosable, but one pair exhibits such morphological overlap that they can be considered cryptic. Molecular and morphological data justify the re-instatement of a broadly circumscribed ecologically variable R. strangulata, of R. mittenii, and the description of five new species. Two species Radula mittenii Steph. and R. notabilis sp. nov. are endemic to the Wet Tropics Bioregion of north-east Queensland, suggesting high diversity and high endemism might characterise the bryoflora of this relatively isolated wet-tropical region. Radula demissa sp. nov. is endemic to southern temperate Australasia, and like R. strangulata occurs on both sides of the Tasman Sea. Radula imposita sp. nov. is a twig and leaf epiphyte found in association with waterways in New South Wales and Queensland. Another species, R. pugioniformis sp. nov., has been confused with Radula buccinifera but was not included in the molecular phylogeny. Morphological data suggest it may belong to subg. Odontoradula. Radula buccinifera is endemic to Australia including Western Australia and Tasmania, and to date is known from south of the Clarence River on the north coast of New South Wales. Nested within R. buccinifera is a morphologically distinct plant from Norfolk Island described as R. anisotoma sp. nov. Radula australiana is resolved as monophyletic, sister to a species occurring in east coast Australian rainforests, and nesting among the R. buccinifera lineages with strong support. The molecular phylogeny suggests several long-distance dispersal events may have occurred. These include two east-west dispersal events from New Zealand to Tasmania and south-east Australia in R. strangulata, one east-west dispersal event from Tasmania to Western Australia in R. buccinifera, and at least one west-east dispersal from Australia to New Zealand in R. australiana. Another west-east dispersal event from Australia to Norfolk Island may have led to the budding speciation of R. anisotoma. In contrast, Radula demissa is phylogeographically subdivided into strongly supported clades either side of the Tasman Sea, suggesting long distance dispersal is infrequent in this species.
Highlights
Crypsis is thought to be a widespread phenomenon in bryophytes (Bischler and Boisselier-DuBayle 1997; Shaw 2001)
Our results provide the first demonstration of cryptic species in Radula, and one of the most extreme cases yet documented in liverworts in terms of neglected diversity uncovered by phylogenetic data
Molecular investigations at species level often find conflict between Linnean classifications and phylogenetic relationships even when species taxonomy based on morphology is well resolved (e.g. Heinrichs et al 2009a, 2012)
Summary
Crypsis is thought to be a widespread phenomenon in bryophytes (Bischler and Boisselier-DuBayle 1997; Shaw 2001). Cryptic and semi-cryptic lineages have been demonstrated in more than 200 studies of bryophyte species (Heinrichs et al 2006), and most major liverwort lineages including Porellales (Ramaiya et al 2010; Heinrichs et al 2009a, 2010; Hentschel et al 2007; Renner et al 2011); Jungermanniales (Feldberg et al 2007); Metzgeriales (Wachowiak et al 2007; Preussing et al 2010; Fiedorow et al 2001; Fuselier et al 2009); and the complex thalloid genera Conocephalum (Odrzykoski and Szweykowski 1991; Szweykowski et al 2005), Reboulia (Boisselier-Dubayle et al 1998) and Dumortiera (Forrest et al 2011). Radula is highly divergent within Porellales (see Schuster 1980) and is Integrative taxonomy resolves the cryptic and pseudo-cryptic Radula buccinifera
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