Genetic and environmental sources of variation in leaf morphology of Sphagnum fallax and Sphagnum isoviitae (Bryopsida): comparison of experiments conducted in the field and laboratory

Gametophores from mixtures of the closely related Sphagnum fallax (H. Kling gr.) H. Klinggr. and Sphagnum isoviitae Flatberg, from two localities were clonally propagated in axenic culture and back transplanted from laboratory to field conditions, as well as reciprocally transplanted between the same localities. Genetic and environmental effects on leaf morphology were esti mated to assess the taxonomic merit of these characters. Differences betwee n populations exceeded between-taxon differences and could not be taken as evidence of two separate species. Plastic responses were apparent in the re ciprocal transplant experiment, and a species-specific norm of reaction cou ld be discerned in one character. Compared with the field experiments the s pecies- and population-level genetic variances increased in the laboratory. This indicates that increased differences between species and populations were an artefact of experimental conditions, rather than caused by environm ental effects opposing genetic effects on morphology in the field. Among-cl one variances remained relatively stable across all experiments, as did res idual variances indicating that the clonal propagation process did not elev ate developmental noise. Contrasting responses between clonally propagated and field collected gametophores provide indirect evidence of changing leve ls of genetic and plastic variation throughout ontogeny.