Radiation and Repeated Transoceanic Dispersal of Schoeneae (Cyperaceae) Through the Southern Hemisphere
• Premise of the study: The broad austral distribution of Schoeneae is almost certainly a product of long-distance dispersal. Owing to the inadequacies of existing phylogenetic data and a lack of rigorous biogeographic analysis, relationships within the tribe remain poorly resolved and its pattern of radiation and dispersal uncertain. We employed an expanded sampling of taxa and markers and a rigorous analytic approach to address these limitations. We evaluated the roles of geography and ecology in stimulating the initial radiation of the group and its subsequent dispersal across the southern hemisphere. • Methods: A dated tree was reconstructed using reversible-jump Markov chain Monte Carlo (MCMC) with a polytomy prior and molecular dating, applied to data from two nuclear and three cpDNA regions. Ancestral areas and habitats were inferred using dispersal-extinction-cladogenesis models. • Key results: Schoeneae originated in Australia in the Paleocene. The existence of a "hard" polytomy at the base of the clade refl ects the rapid divergence of six principal lineages ca. 50 Ma, within Australia. From this ancestral area, Schoeneae have traversed the austral oceans with remarkable frequency, a total of 29 distinct dispersal events being reported here. Dispersal rates between landmasses are not explicable in terms of the geographical distances separating them. Transoceanic dispersal generally involved habitat stasis. • Conclusions: Although the role of dispersal in explaining global distribution patterns is now widely accepted, the apparent ease with which such dispersal may occur has perhaps been under-appreciated. In Schoeneae, transoceanic dispersal has been remarkably frequent, with ecological opportunity, rather than geography, being most important in dictating dispersal patterns.
Systematic Studies in 'Schoenus' L. (Schoeneae, Cypearaceae)
Infra- and suprageneric classification of 'Schoenus' is uncertain. Like other Cyperaceae, 'Schoenus' L. and allied genera have reduced vegetative and reproductive structures which have resulted in uncertain homologies and hence differences in opinion about its phylogenetic relationships. This study addresses the issues of phylogeny, species limits and usefulness of anatomical data in the genus. Phylogenetic analysis of 195 ingroup samples made up of 123 samples covering 74 species of 'Schoenus' and 72 samples across 56 species from 11 genera in tribe Schoeneae was conducted on a molecular sequence dataset from ITS nrDNA using maximum parsimony and Bayesian inference. Results indicated that 'Schoenus' is non-monophyletic, which corroborates small-scale previous molecular studies. 'Schoenus' subgen. 'Schoenus' had strongly supported lineages whereas S. subgen. 'Pseudomesomelaena', including 'S. grandiflorus', are embedded within other genera in Schoeneae and therefore not in core 'Schoenus'. The ITS data did not fully resolve relationships of 'Schoenus' at species level, but revealed numerous well supported terminal groupings and taxa allowing for further fine-scale study of the complexes to resolve limits and application of names. ... Taxonomic value of culm anatomy has been investigated using phenetic analysis. The results show culm anatomical features have taxonomic value in 'Schoenus' at and below species level and help to clarify patterns of variation at infra and interspecific level and to resolve species complexes. Phylogenetic analysis, however, indicated that the dataset had no power to resolve higher level relationships within 'Schoenus'. A new species has been distinguished from 'S. melanostachys' using morphology and integrating evidence from culm anatomy and scanning electron microscopy.