Contribution to the knowledge of genome size variation in Calendula L. (Asteraceae) with special focus on the SW Mediterranean region

Abstract

Calendula is one of the most taxonomically complex genera within the Asteraceae family due to hybridization, polyploidization events, and production of a highly variable morphology of the achenes. Considering the complexity of Calendula, this study was conducted to extend the understanding of the relationships between SW Mediterranean taxa, and assess the relationships between genome size and chromosome number, ploidy level and life cycle in 77 populations covering 14 taxa. Genome size estimations are provided for the first time for five species and for three putative new undescribed species. Mean 2C values differed up to 6-fold among different euploid species (from 1.37 pg in diploid to 8.26 pg in octoploid populations). 1Cx-values varied 2.07-fold (between 0.68 pg and 1.41 pg). Mean 1Cx genome size revealed significant differences between different ploidy levels. Genome size variation is a significant factor for explaining the relationships within Calendula, and individuals not fitting the current classification were found and should be analysed in detail in future studies.