SHANER, MARIEKEN G.M.* and DIANE L. MARSHALL. University of New Mexico-Department of Biology Albuquerque, NM 87131. - Under how wide a set of conditions will nonrandom mating occur in Raphanus sativus?
Sexual selection has been shown to be a powerful evolutionary force in
animals, however in plants it has been more controversial. Research
with the weedy annual Raphanus sativus has demonstrated that
nonrandom mating can occur in greenhouse plants. We asked whether this
nonrandom mating can occur under a wide range of conditions, including
conditions that might occur in the field. To answer this question we
constructed a continuum of treatments including variation in both
maternal condition and pollen load size. Maternal condition was varied
by altering the watering regime. Pollen load size was varied from 30
to 400 pollen grains per stigma. Seed siring success was influenced by
the pollen donor and the maternal family. Additionally, maternal
condition and pollen load size had an effect on seed siring success.
The results suggest that there is a threshold below which nonrandom
mating does not occur.
Key words: nonrandom mating, pollen load size, Raphanus sativus