Karyotypes, heterochromatin distribution and rDNA patterns in South American Grindelia (Asteraceae)

Abstract

Grindelia is a genus with a complex evolutionary history with reticulate evolution. We studied the karyotype, fluorescent banding, and fluorescence in situ hybridization (FISH) using 18–5.8–26 S and 5 S ribosomal DNA probes to survey karyotypic diversity of South American Grindelia species. Chromosome basic numbers were x = 6 (with several ploidy levels: 2x, 4x, and 6x). All the Grindelia studied conserved the patterns of CG-rich heterochromatin and 18-5.8-26 S rDNA. The third m sat-chromosome pair was homeologous in Grindelia. Chromosome variation, although not always large, accompanied the evolutionary divergence of the taxa studied. The Grindelia studied formed two species groups: (1) G. globularifolia and G. pulchella var. pulchella, (2) G. buphthalmoides, G. cabrerae var. alatocarpa and var. cabrerae, G. chiloensis, G. orientalis, and G. prostrata. These groups do not show any morphological affinities and their phylogenetic relationships are not clearly resolved, suggesting that these groups have recently diverged.

Keywords:

• Grindelia
• heterochromatin
• karyotype
• polyploidy
• ribosomal genes

Acknowledgments

Dr. Chiarini Franco (IMBIV) kindly sent samples. Grants from “Consejo Nacional de Investigaciones Científicas y Técnicas” (CONICET, Argentina) and “Universidad Nacional de Córdoba” (SECyT, Argentina) are acknowledged.