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.
Acknowledgements
We thank anonymous reviewers for the suggestions, and William Smith for the English revision, that greatly improved the manuscript. Thanks are also due to several herbaria (ABH, AL (ENSA), ARAN, B, BC (IBB), BCN, BM, BONN, BR, C, COI, E, ELVE, FI, G, GAT, GDA (GDAC), HAL, JACA, JAEN, JE, K, LD, LEB, LISI, M, MA, MACB, MAF, MARK, MGC, MPU, O, P, PO, RAB, RNG, SALA, SANT, SEV, TFMC, US, VAL and W) for allowing the study or loaning plant material of Calendula. We are very grateful to several institutions that have authorized collections of Calendula specimens, namely: Instituto da Conservação da Natureza e das Florestas (Portugal), Parque Nacional de las Islas Atlanticas de Galicia y Parque Natural de la Sierra de las Nieves (Spain), Jbilet Reserve (Morocco). We also thank for the achene samples provided by: Real Jardín Botanico de Madrid (CSIC), USDA, IPGN, Olofron Plume (Cornell University, Ithaca, United States), Stephen Mifsud (Malta) and Miguel Sequeira (Univ. of Madeira, Portugal).
Disclosure statement
The authors declare that they have no conflict of interest.