Sex differences in floral nectar production bySilene latifolia(Caryophyllaceae), with reference to susceptibility to a pollinator-borne fungal disease

Abstract

Nectar production and concentration were measured on male and female plants of six experimental lines of Silene latifolia (Caryophyllaceae) that differ in disease resistance. Differences between the sexes and among the lines were found for nectar production, concentration, and total sugar production during the first 24 h of anthesis. Females produced more nectar of lower concentration than did males, and males secreted more sugar than did females during the first day of anthesis. However, nectar traits of males and females resembled one another within a line, suggesting a genetic correlation between the sexes. Further, the additive genetic basis for this trait appears weak. In S. latifolia repeatabilities for nectar traits were low and differed between females and males, so the heritabilities must be extremely low. Groups of plant lines that are "susceptible" and "resistant" to the fungal pathogen Microbotryum violaceum did not differ in nectar parameters. Therefore resistance to this pollinator-borne disease does not appear to influence nectar production. Key words: Microbotryum (= Ustilago), plant – pathogen interactions, pollinator reward, anther-smut disease, dioecy, floral nectar.