Evidences towards a Genetic Differentiation and Karyotype Evolution of the Sedges Cyperus odoratus L and C Ligularis L (Cyperaceae)

Abstract

Cyperaceae is composed of pioneer species and presents a complex taxonomy, with genera like Cyperus presenting specific complexes. The aim of this study was to analyze the genetic diversity between the broadly distributed sedges Cyperus ligularis L. and C. odoratus L using DNA fingerprinting markers and cytogenetic features, focusing on collection sites from an Atlantic Forest reserve and its surroundings in the city of Recife (Pernambuco, Brazil). Both the significative genetic diversity (GST = 0.363) and the low gene flow (Nm = 0.877) were found and indicated a clear genetic differentiation between the two species. Moreover, the clustering analysis showed the presence of two distinct genetic groups, also suggesting no evidence of hybridization between C. ligularis and C. odoratus. Regarding the phenogram topology, the species are also two clear different lineages, and although all individuals of C. odoratus were collected in nearby plots, they showed a greater intraspecific genetic variability than that observed among individuals of C. ligularis, which were sampled in a wider geographic range. However, the variation in chromosome numbers within the two species showed an opposite pattern, indicating higher karyotype stability in C. odoratus. Furthermore, the lowest genetic differentiation in C. ligularis may reflect a founder effect associated with the ability to disperse seeds and colonize multiple areas. Further field observations, as well as an analysis of reproductive biology, should enrich the understanding of the genetic structure of the populations investigated and the role of these plants in successional processes.