XVI International Botanical Congess

Phenotypic evolution is typically addressed in quantitative terms, attributing variation underlying genetic loci. We have established a negative genetic relationship between an AT-biased flow cytometric measure of nuclear DNA content and calyx diameter across lineages of Silene latifolia (Caryophyllaceae) subjected to selection for increases or decreases in calyx diameter, suggesting that repetitive DNA (often regarded as junk or selfish DNA with little or no phenotypic significance) plays an important role in phenotypic response to selection. More recently, we have analyzed covariation in DNA content and calyx diameter among different species of Silene Sect. Elisanthe, which includes S. latifolia. Our present results show that variation in DNA content may play a longer-term role in differentiation between species.