MOLECULAR PHYLOGENY OF GYMNOCALYCIUM (CACTACEAE)

DEMAIO, P.H. ; BARFUSS, M.H.J.; KIESLING, R; TILL, W; CHIAPELLA, J

AMERICAN JOURNAL OF BOTANY

BOTANICAL SOC AMER INC

Lugar: St. Louis; Año: 2011 vol. 98 p. 1841 - 1854

0002-9122

Premise of the study: The South American genus Gymnocalycium (Cactoideae-Trichocereae) demonstrates how the sole use of morphological data in Cactaceae results in confl icts in assessing phylogeny, constructing a taxonomic system, and analyzing trends in the evolution of the genus. ? Methods: Molecular phylogenetic analysis was performed using parsimony and Bayesian methods on a 6195-bp data matrix of plastid DNA sequences ( atpI-atpH , petL-psbE , trnK-matK , trnT-trnL-trnF ) of 78 samples, including 52 species and infraspecifi c taxa representing all the subgenera of Gymnocalycium . We assessed morphological character evolution using likelihood methods to optimize characters on a Bayesian tree and to reconstruct possible ancestral states. ? Key results: The results of the phylogenetic study confi rm the monophyly of the genus, while supporting overall the available infrageneric classifi cation based on seed morphology. Analysis showed the subgenera Microsemineum and Macrosemineum to be polyphyletic and paraphyletic. Analysis of morphological characters showed a tendency toward reduction of stem size, reduction in quantity and hardiness of spines, increment of seed size, development of napiform roots, and change from juicy and colorful fruits to dry and green fruits. ? Conclusions: Gymnocalycium saglionis is the only species of Microsemineum and a new name is required to identify the clade including the remaining species of Microsemineum ; we propose the name Scabrosemineum in agreement with seed morphology . Identifying morphological trends and environmental features allows for a better understanding of the events that might have infl uenced the diversifi cation of the genus.