title: Phylogenetic relationships and evolution of growth form in Cactaceae (Caryophyllales, Eudicotyledoneae).
abstract: OBJECTIVE
  Cactaceae is one of the most charismatic plant families because of the extreme succulence and outstanding diversity of growth forms of its members. Although cacti are conspicuous elements of arid ecosystems in the New World and are model systems for ecological and anatomical studies, the high morphological convergence and scarcity of phenotypic synapomorphies make the evolutionary relationships and trends among lineages difficult to understand.
  
  
  METHODS
  We performed phylogenetic analyses implementing parsimony ratchet and likelihood methods, using a concatenated matrix with 6148 bp of plastid and nuclear markers (trnK/matK, matK, trnL-trnF, rpl16, and ppc). We included 224 species representing approximately 85% of the family's genera. Likelihood methods were used to perform an ancestral character reconstruction within Cactoideae, the richest subfamily in terms of morphological diversity and species number, to evaluate possible growth form evolutionary trends.
  
  
  RESULTS
  Our phylogenetic results support previous studies showing the paraphyly of subfamily Pereskioideae and the monophyly of subfamilies Opuntioideae and Cactoideae. After the early divergence of Blossfeldia, Cactoideae splits into two clades: Cacteae, including North American globose and barrel-shaped members, and core Cactoideae, including the largest diversity of growth forms distributed throughout the American continent. Para- or polyphyly is persistent in different parts of the phylogeny. Main Cactoideae clades were found to have different ancestral growth forms, and convergence toward globose, arborescent, or columnar forms occurred in different lineages.
  
  
  CONCLUSIONS
  Our study enabled us to provide a detailed hypothesis of relationships among cacti lineages and represents the most complete general phylogenetic framework available to understand evolutionary trends within Cactaceae.
authors: Departamento de Botánica, Instituto de Biología, Universidad Nacional Autónoma de México, 3er Circuito de Ciudad Universitaria, Del. Coyoacán, México D.F. 04510 México.
authors: Tania
authors: T
authors: Hernández-Hernández
authors: Héctor M
authors: HM
authors: Hernández
authors: J Arturo
authors: JA
authors: De-Nova
authors: Raul
authors: R
authors: Puente
authors: Luis E
authors: LE
authors: Eguiarte
authors: Susana
authors: S
authors: Magallón