Phylogenetic reconstruction of the genus Tephrocactus (Cactaceae) based on molecular, morphological, and cytogenetical data

LAS PEÑAS, M. L.; KIESLING, R; BERNARDELLO, G.

TAXON

INT ASSOC PLANT TAXONOMY

Lugar: Viena; Año: 2019

0040-0262

Abstract Tephrocactus comprises species mainly endemic to Argentina. Molecular phylogenetic analyses of all species of the genus, as well as classical (chromosome number, karyotype) and molecular cytogenetical techniques (DNA content, heterochromatin amount, rDNA genes) were conducted. Sequence data of two plastid DNA markers of Tephrocactus taxa were analyzed. Evolution of character states of cytogenetical and morphological (growth form, presence of leaves, glochids and tepal spiny mucrons, flower color) were reconstructed. Species show x = 11 with different ploidy levels (2n = 22, 44, 66, 77, 242, 319), small chromosomes, and symmetrical karyotypes. Tephrocactus was recovered as monophyletic with three main clades including 12 species, using molecular and morphological data. Tephrocactus geometricus, T. halophilus, and T. paediophilus are recognized as a good species. Banding patterns showed CMA+/DAPI? constitutive heterochromatin associated with nuclear organized regions. Heterochromatin amount ranged from 2.99 to 6.0%. The 18S?5.8S?26S ribosomal DNA (rDNA) sites coincided with the CMA+/DAPI− signals. 5S sites varied with ploidy levels of the taxa. DNA content (2C = 1.99-24.50 pg) had a significant and positive correlation with the ploidy level and the number of rDNA genes. The ancestor is reconstructed to have been dwarf shrub with strong articulation, glochids, and deciduous leaves, white, pink or pearly tepals without spiny mucrons, with 2n = 22, low DNA content, and one pair of each rDNA gen followed by three polyploidization events. Tephrocactus diversification has been associated with polyploidy and few cumulative small cryptic chromosomal changes.