Genome size variation in the genus Andryala (Hieraciinae, Asteraceae)

Abstract

The genus Andryala includes diploid plants distributed in the Mediterranean Basin, Macaronesia and in one isolated outpost in the Romanian Carpathians. We analysed nuclear genome size in a phylogenetic framework and assessed relationships between genome size and life form (perennials vs annuals/biennials) and the consequences of insular vs continental distribution. Absolute nuclear genome size of 18 species or subspecies was determined using propidium iodide flow cytometry. The evolution of genome size was investigated using the Brownian motion model with the tree scaling parameters λ, κ and δ. The mean 2C values differs up to 1.84-fold between species (from 2.69 to 5.01 pg). Chromosome numbers of six species are reported for the first time. The highest 2C values are present in two well supported basal lineages corresponding to the relict species A. laevitomentosa and A. agardhii. The rest of Andryala species that form a well-supported clade of closely related species (the ‘Major Radiation Group’), except for two populations of A. ragusina, have significantly smaller genome sizes. In the ‘Major Radiation Group’, genome size in perennial species is significantly greater compared to annual and biennial species. With a possible bias caused by A. dentata and A. integrifolia, insular species of the ‘Major Radiation Group’ have lower nuclear genomes than continental ones. The genome size variation contains strong phylogenetic signal, which could indicate that genome size in the group under study is not greatly influenced by selection and is probably a result of neutral evolution or genetic drift.