Variation in sexual and asexual reproduction among young and old populations of the perennial macrophyte Sparganium erectum

We examined how population age affects the relative importance of clonal propagation and sexual reproduction in the aquatic macrophyte Sparganium errectum. Plants were collected from two newly established populations and four successionally mature populations. The comparison of life history traits associated with sexual reproduction and clonal multiplication was carried out in a controlled environment experiment. We found that several physiological trade-offs occurred between sexual reproduction and clonal propagation. Moreover, we found a higher investment in sexual reproduction in newly established populations than in older populations. These results suggest that clonal propagation is favoured at the population level while, because seeds produced by sexual reproduction are the only means for long distance dispersal, selection will favour sexual reproduction at the metapopulation level. This discrepancy between selective pressures at different spatial scales could favour the maintenance of a mixed sexual-asexual reproductive system in Sparganium erectum.