Variation of sexual and clonal reproduction in the alpine Geum reptans in contrasting altitudes and successional stages

We studied the relative proportion of sexual vs. clonal reproduction in 20 populations of the alpine pioneer plant Geum reptans in response to altitude (low and high) and succession (early and late). Additionally, the proportion of life-cycle stages, the proportion of reproducing adults, seed size, and seed number per flower head were determined. With increasing plant size, the probability of producing both flower heads and stolons increased (P < 0.001). Individuals of all size classes tended to produce more flower heads than stolons. Stolon production was more frequent only if plants reproduced by one reproductive mode (P < 0.05). The significant difference among populations in sexual reproduction and of seed number per flower head was not explained by habitat type. However, clonal reproduction was higher in populations at low and high altitude compared to populations at intermediate altitude (P < 0.05). High altitude populations were characterised by a tendency of small plants to decline and an increase in the proportion of large plants (P < 0.05) whereas the proportion of reproducing adults did not change with altitude. This indicates not only lower recruitment but also, that after successful establishment, growth and reproduction in G. reptans are not generally restricted, even above 2850 m. Our results suggest that variation in the proportion of sexual and clonal reproduction in G. reptans is probably more shaped by individual, i.e. plastic responses to local environmental conditions than by environmental gradients. (c) 2005 Gesellschaft fur Okologie. Published by Elsevier GmbH. All rights reserved.