Ultimate costs of sporophyte production in the clonal moss Hylocomium splendens

Abstract

A richly sporophyte-producing population of the dioecious perennial clonal moss Hylocomium splendens was followed for five years in order to investigate the longterm costs of sporophyte production. Female mature segments were divided into two subpopulations: sporophyte producing and reference without sporophytes. Ultimate (long-term) population growth rates of l 5 1.091 and 1.258, respectively, were found for the two subpopulations by building separate deterministic transition matrix models. By bootstrapping each subpopulation, the difference in l between subpopulations was found to be significant (P , 0.001). Life-table response experiment analysis attributed the lower population growth rate of the SP subpopulation to inferior ramification rates, lower survival, and inferior size development of mature segments. Considerable variation in H. splendens sporophyte production among years indicates large among-year variation in investment in sexual reproduction, probably related to resource status. Establishment of H. splendens from spores in natural habitats has never been observed. Nevertheless, sexual spores may play a role in establishment of H. splendens populations on new substrates.

Key words: bootstrapping; boreal forest (southeastern Norway); bryophyte; clonal plant; elasticity; Hylocomium splendens; life-table response experiment; matrix models; models, transition matrix; population growth rate; sexual reproduction; somatic costs.