The relative contributions of seed and pollen movement to the local genetic structure of Silene alba

Silene alba is an insect-pollinated weedy plant that is distributed into numerous ephemeral roadside patches in the study area in southwestern Virginia, Gene flow in S. alba arises as a consequence of the movement of two life stages, seeds and pollen, In an effort to evaluate the relative contributions of seed and pollen movement to total gene flow, genetic structure was estimated from among-population allele frequency variation using allozymes, the product of nuclear genes that can move in either seeds or pollen, and chloroplast DNA (cpDNA), which if maternally inherited can move only in seeds, Genetic structure was evaluated at three spatial scales-among collections separated by kilometers, tens of meters, and meters, Among-population allele frequency variation was much greater in cpDNA than in allozymes at all spatial scales, The ratio of pollen to seed movement was estimated from these data to range from 3.4 at the largest spatial scale to 124.0 at the finest scale, The broader application of maternally inherited genetic markers to questions in plant population biology is also discussed.