Studying evolutionary constraints on an invariant floral trait in Wild Radish Raphanus raphanistrum
Fergus, C. Emi
Traits that are conserved through time and location are considered invariant characters. In the flowering world, these floral traits are useful in classifying plants. Little is known about the mechanisms that maintain these invariant traits. There are three non-mutually exclusive hypotheses to explain restricted variability of traits: 1) Little genetic variation; 2) Stabilizing selection; 3) Evolutionary constraints taking the form of physical, chemical, or developmental constraints. In the plant Raphanus raphanistrum (wild radish) there is a high correlation between filament height and corolla tube length. The position of the anther is referred to as anther exsertion. Anther exsertion can be calculated from the differences in filament height and corolla tube length. In natural populations, anther exsertion is zero with the anthers positioned at the opening of the corolla tube.
1 broadside ; ill.