Genome size comparison in Colobanthus quitensis populations show differences in species ploidy

摘要

Colobanthus quitensis is the only native dicotyledoneae in the Antarctic; therefore, it is the object of ample research regarding tolerance mechanisms to its extreme habitat. This species also represents a wide geographical distribution, from 68 degrees S to 17 degrees N and from 0 m a.s.l. in the south to 4200 m a.s.l. in the north of its distribution area. As the described habitats for different populations coincide in their extreme abiotic characteristics, there has been increasing interest in studying different populations in recent years, as well as the existence of phenotypic or genetic variability among them. In contrast, very little is known about its genome; knowledge of genome size and ploidy levels allows the development of strategies to generate information in population studies related to structure, gene flow and genetic diversity in order to describe phenotypic characteristics. Several studies have related genome size to the ecological requirements of the species distributed through an ample environmental gradient. For several years now, flow cytometry has become a simple method to determine genome size in a wide variety of species. In this paper, we determine genome size for three C. quitensis populations. The populations of Arctowski and La Marisma (Punta Arenas) have 2C = 1.95 pg, while the Conguillio population reported 2C = 0.84 pg, approximately half as much. This may evidence different ploidy levels between the populations, creating new questions with regard to the number of chromosomes and the possible existence of endopoliploidy. This would be related to the distribution and the adaptive mechanisms of this species throughout its wide distribution.