PROGENY SEX-RATIOS IN DIOECIOUS SILENE-LATIFOLIA (CARYOPHYLLACEAE)

Most sex ratios reported for Silene latifolia are female biased. As a result of experiments performed by Correns in the early 1900s, pollen tube competition has generally been accepted as the primary cause of t hese skewed ratios. We did four sets of hand pollinations in which we varied the size of pollen loads and placement of pollen along the fila mentous stigma. The effect of pollen load size on progeny sex ratios w as not statistically significant. Of 32 maternal families, 17 containe d more females than males (one ratio deviated statistically from 1:1), and 13 contained more males than females. Paternal families exhibited a greater range of sex ratios, including three with a significant fem ale bias and one with a significant male bias. Within experiments. nei ther thy maternal parent nor where pollen was placed had a statistical ly significant effect on progeny sex ratios; the paternal effect was s ignificant in one experiment. We suggest that sex ratios in Silene lat ifolia are not necessarily affected by the level of pollen competition . Other factors, including variation among males and sex-linked mortal ity, may help explain the skewed sex ratios that characterize populati ons of this species. Further, Correns' observations of excess females may have resulted from his use of interspecific hybrids.