Floral morphology and stigma-anther separation in gynomonoecious-gynodioecious Kosteletzkya virginica (Malvaceae)

A morphometric study of 13 floral traits in hermaphrodites and females of Kosteletzkya virginica was conducted to test the hypothesis that sexual dimorphism in corolla size can be explained entirely by size of the androecium (vestigial in females), as predicted by the corolla-androecium developmental correlation hypothesis. Hermaphrodites of K. virginica significantly exceeded females in size for most corolla dimensions. Overall, size of the corolla thus appears to be primarily a stamen-correlated trait. These results are consistent with the corolla-androecium developmental correlation hypothesis that the androecium is an important regulatory organ for floral development and that one pleiotropic effect of male sterility in K. virginica has been a reduction in corolla size. However, style length and basal diameter of the stamen column did not conform to this pattern, indicating that these traits are more independent of androecium function than most dimensions of corolla size. Herkogamy in K. virginica was 3.31 ± 0.04mm (n = 760), ranging from 0.9mm to 7.4mm. Herkogamy is highly variable within the naturalised population of K. virginica, and not correlated with all measured floral traits in hermaphrodites and females. Decreases in stigma-anther distance over the flowering day provide the potential for delayed autonomous selfing.