title: Phylogeny, biogeography and ecological diversification of Sarcocornia (Salicornioideae, Amaranthaceae).
abstract: OBJECTIVE
  Sarcocornia comprises about 28 species of perennial succulent halophytes distributed worldwide, mainly in saline environments of warm-temperate and subtropical regions. The genus is characterized by strongly reduced leaves and flowers, which cause taxonomic difficulties; however, species in the genus show high diversity in growth form, with a mat-forming habit found in coastal salt marshes of all continents. Sarcocornia forms a monophyletic lineage with Salicornia whose species are all annual, yet the relationship between the two genera is poorly understood. This study is aimed at clarifying the phylogenetic relationship between Sarcocornia and Salicornia, interpreting biogeographical and ecological patterns in Sarcocornia, and gaining insights into putative parallel evolution of habit as an adaptation to environmental factors.
  
  
  METHODS
  A comprehensively sampled and dated phylogeny of Sarcocornia is presented based on nuclear ribosomal DNA (external transcribed spacer) and chloroplast DNA (atpB-rbcL, rpl32-trnL) sequences; representative samples of Salicornia were also included in the analyses. To infer biogeographical patterns, an ancestral area reconstruction was conducted.
  
  
  RESULTS
  The Sarcocornia/Salicornia lineage arose during the Mid-Miocene from Eurasian ancestors and diversified into four subclades: the Salicornia clade, the American Sarcocornia clade, the Eurasian Sarcocornia clade and the South African/Australian Sarcocornia clade. Sarcocornia is supported as paraphyletic, with Salicornia nested within Sarcocornia being sister to the American/Eurasian Sarcocornia clade. The American and the South African/Australian Sarcocornia clade as well as the Salicornia clade were reconstructed to be of Eurasian origin. The prostrate, mat-forming habit arose multiple times in Sarcocornia.
  
  
  CONCLUSIONS
  Sarcocornia diversified in salt-laden environments worldwide, repeatedly evolving superficially similar prostrate, mat-forming habits that seem advantageous in stressed environments with prolonged flooding, high tidal movement and frost. Some of these prostrate-habit types might be considered as ecotypes (e.g. S. pacifica or S. pillansii) while others represent good ecospecies (e.g. S. perennis, S. decumbens, S. capensis), hence representing different stages of speciation.
authors.affiliation: Institute für Allgemeine und Spezielle Botanik, Johannes Gutenberg-Universität Mainz, Germany, Biology Department, University of Toronto at Mississauga, Mississauga, ON, L5L 1C6, Canada and School of Plant Biology, The University of Western Australia, 35 Stirling Hwy, Crawley WA 6009, Perth, Australia; Department of Geography & Environmental Studies, Stellenbosch University, Private Bag X1, Matieland 7602, Stellenbosch, South Africa.
authors.forename: Simone
authors.initials: S
authors.lastname: Steffen
authors.affiliation: Institute für Allgemeine und Spezielle Botanik, Johannes Gutenberg-Universität Mainz, Germany, Biology Department, University of Toronto at Mississauga, Mississauga, ON, L5L 1C6, Canada and School of Plant Biology, The University of Western Australia, 35 Stirling Hwy, Crawley WA 6009, Perth, Australia; Department of Geography & Environmental Studies, Stellenbosch University, Private Bag X1, Matieland 7602, Stellenbosch, South Africa.
authors.forename: Peter
authors.initials: P
authors.lastname: Ball
authors.affiliation: Institute für Allgemeine und Spezielle Botanik, Johannes Gutenberg-Universität Mainz, Germany, Biology Department, University of Toronto at Mississauga, Mississauga, ON, L5L 1C6, Canada and School of Plant Biology, The University of Western Australia, 35 Stirling Hwy, Crawley WA 6009, Perth, Australia; Department of Geography & Environmental Studies, Stellenbosch University, Private Bag X1, Matieland 7602, Stellenbosch, South Africa.
authors.forename: Ladislav
authors.initials: L
authors.lastname: Mucina
authors.affiliation: Institute für Allgemeine und Spezielle Botanik, Johannes Gutenberg-Universität Mainz, Germany, Biology Department, University of Toronto at Mississauga, Mississauga, ON, L5L 1C6, Canada and School of Plant Biology, The University of Western Australia, 35 Stirling Hwy, Crawley WA 6009, Perth, Australia; Department of Geography & Environmental Studies, Stellenbosch University, Private Bag X1, Matieland 7602, Stellenbosch, South Africa clausing@uni-mainz.de.
authors.forename: Gudrun
authors.initials: G
authors.lastname: Kadereit
mesh_terms: D027703:Amaranthaceae / Q000145:classification* / Q000235:genetics / Q000502:physiology*; D005075:Biological Evolution; D021901:DNA, Intergenic / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D063148:Plant Dispersal; D055049:Salt Tolerance; D055051:Salt-Tolerant Plants / Q000235:genetics / Q000502:physiology*; D017422:Sequence Analysis, DNA
chemical_list: D021901:DNA, Intergenic; D018744:DNA, Plant
keywords: Africa; Australia; Chenopodiaceae; Mediterranean; Salicornia; Sarcocornia; South America; ecospecies; ecotypes; flooding tolerance; growth form plasticity; halophytes; salinity