Effects of brooding and broadcasting reproductive modes on the population genetic structure of two Antarctic gastropod molluscs

Life-history characteristics exert a profound influence upon the population structure of many marine organisms. However, relatively few genetic studies have compared direct with indirect-developing species in the same ecosystem or geographical region, and none to our knowledge within an Antarctic setting. To address this issue, we have collected novel amplified fragment length polymorphism (AFLP) data from the direct-developing top shell Margarella antarctica to form a comparison with previously published data for the broadcast-spawning Antarctic limpet Nacella concinna. We scored 270 loci in 240 M. antarctica individuals sampled from five populations spanning the full length of the Antarctic Peninsula. Profound differences were identified in the strength and pattern of population structure between the two species, consistent with gene flow being highly restricted in M. antarctica relative to N. concinna.