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Scheben, Armin; Bechteler, Julia; Lee, Gaik Ee; Pócs, Tamás; Schäfer-Verwimp, Alfons; Heinrichs, Jochen (2016): Multiple transoceanic dispersals and geographical structure in the pantropical leafy liverwort Ceratolejeunea (Lejeuneaceae, Porellales). In: Journal of Biogeography, Vol. 43, No. 9: pp. 1739-1749
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Abstract

AimHow disjunct distributions arise and why organisms differ in diversification patterns remain some of the most compelling fundamental questions in biogeography. We carry out phylogeographical analyses of the pantropical liverwort genus Ceratolejeunea to identify its geographical origin and the dispersal routes by which it gained its Neotropical-African disjunction. Furthermore, we investigate whether there is geographical structure in Ceratolejeunea on islands and whether island diversity is a result of radiations or recurrent migration. LocationAmerica, Africa and Australasia. MethodsSequences of two chloroplast regions (trnL-F, rbcL) and the nuclear ribosomal ITS region were obtained for 55 accessions of 20 species to explore the phylogeny, divergence times and ancestral areas of Ceratolejeunea. The phylogeny was reconstructed using maximum likelihood and Bayesian inference approaches, and divergence times were estimated with a Bayesian relaxed clock method and fossil and secondary calibrations. Ancestral areas were estimated using BioGeoBEARS. ResultsCeratolejeunea likely originated in the Neotropics during the Palaeogene (42.2Ma, 95% HPD: 22.2-64.8) and the initial diversification of its crown group took place between the Eocene and Miocene (25.5Ma, 95% HPD: 16.6-35.8). Although boreotropical migration and subsequent extinction in northern regions cannot be rejected, the observed disjunctions are best explained by four transoceanic dispersal events from the Neotropics to Africa during the late Oligocene to Pleistocene. Geographical structure is prevalent on islands, particularly in the C. cornuta complex. Three species and the subgenus Ceratolejeunea are recovered as paraphyletic. Main conclusionsWidespread paraphyly and sister group relationships between disjunct taxa indicate an important role of cryptic speciation and transoceanic dispersal with subsequent genetic differentiation in the evolution of Ceratolejeunea. On islands, recurrent migration, rather than radiation, has shaped bryophyte diversity.