Incipient speciation in Calceolaria polyrhiza complex (Calceolariaceae): Cytogenetic analysis supports molecular and morphological data

Abstract

Calceolaria polyrhiza is a perennial herb distributed in southern South America. The species is highly polymorphic and includes four described morphotypes that were previously considered different species. We performed a detailed study of the karyotype of each morphotype considering at least two localities for each one, with the aim of contributing to the taxonomic delimitation of the Calceolaria polyrhiza complex. In addition, a principal component analysis and a mapping of chromosome traits onto a phylogeny of nuclear DNA sequences were performed. This detailed karyotypic study has revealed specific markers, which have allowed to characterize each morphotype. ‘Prichardii’ morphotype was consistently polyploid. ‘Mendocina’ and ‘Lanceolata’ morphotypes had the highest total heterochromatin amount, with two pairs of chromosomes carrying NORs. ‘Mendocina’ samples showed the most asymmetrical karyotypes. ‘Polyrhiza’ morphotype had the most symmetrical karyotypes of the four morphotypes and the simplest fluorescent chromosome banding pattern. Thus, the four morphotypes could be characterized by chromosomal data and, together with the phylogenetic analysis of molecular data, could be considered taxonomic units in the process of diversification.