Colonization dynamics of the clonal moss Hylocomium splendens on islands in a Baltic land uplift area: reproduction, genet distribution and genetic variation

Summary1 Islands representing four stage classes, dated by their height above sea level, in a Baltic land uplift area were used to study genet level dynamics during colonization of the clonal moss Hylocomium splendens . Allozyme electrophoresis involving 10 polymorphic loci enabled accurate identification of 103 haplotypes from a sample of 694 shoots collected along transects across 10 islands. 2 The populations consisted initially of scattered colonies with single clones. The number of clones, and the tendency of colonies to be multiclonal, increased significantly with increasing age of islands, whilst their mean size decreased significantly. In the Skeppsvik Archipelago, H. splendens thus shows repeated recruitment. 3 The percentage male or female fertile shoots relative to sterile shoots was positively correlated with age of the islands. The sex ratios were skewed during early colonization. 4 Spore capsules were found only in the oldest succession stage‐classes. This can be explained by a greater chance for fertile males and females to grow within the fertilization range, which is limited to a few centimetres. 5 Genetic variation was accumulating with increasing population age. Correlations were stronger for mean number of alleles per locus ( A ) than for gene diversity ( H S ). 6 No isolation by distance was detected among populations, indicating efficient and essentially random gene flow, probably occurring via wind‐dispersed spores.