Variable patterns of seed maturation and abortion in Alliaria petiolata (Brassicaceae)

We investigated variation in ovule development within and among fruits in garlic mustard, Alliaria petiolata (M. Bieb.) Cavara & Grande. Individuals were sampled at 14 sites in North America. On average, 94% of ovules showed evidence of fertilization and development. The majority of ovules (mean 68%; range 53.2-82.5%) reached seed maturity. Patterns of seed maturation and abortion varied nonrandomly within and among fruits. In sites in Tennessee, Kentucky, and Ontario, resource limitation seemed to be an important determinant of seed production, as fruits initiated nearest the base of an infructescence were significantly more likely to produce mature seeds than distally located fruits. Also the probability of seed maturation within individual fruits decreased significantly from the pedicellar to the stylar ends. In contrast, for individuals from Ohio sites, the probability of maturing seeds was greatest for centrally located fruits within an infructescence as well as for centrally located ovules within fruits, indicating a greater influence of pollen limitation in addition to resource limitation. We conclude that it could be misleading to infer traits of a species as a whole based on observed patterns of seed maturation in a single site or region. Rather such patterns may reflect prevailing conditions and selection pressures at a local, or regional, scale.Key words: Alliaria petiolata, Brassicaceae, garlic mustard, ovule abortion, seed maturation, patterns.