POPULATION-STRUCTURE AND INTERSPECIFIC DIFFERENTIATION OF THE PEAT MOSS SISTER SPECIES SPHAGNUM-RUBELLUM AND SPHAGNUM-CAPILLIFOLIUM (SPHAGNACEAE) IN NORTHERN EUROPE
N. Cronberg, POPULATION-STRUCTURE AND INTERSPECIFIC DIFFERENTIATION OF THE PEAT MOSS SISTER SPECIES SPHAGNUM-RUBELLUM AND SPHAGNUM-CAPILLIFOLIUM (SPHAGNACEAE) IN NORTHERN EUROPE, Plant systematics and evolution, 209(3-4), 1998, pp. 139-158
Isozyme electrophoresis was used to study the morphologically similar
sister species Sphagnum rubellum and S. capillifolium from a sample of
1313 plants representing 37 populations from Scandinavia, Great Brita
in and S Germany. The mean pairwise genetic identities (I) among consp
ecific populations were 0.976 for S. rubellum and 0.969 for S. capilli
folium, versus 0.627 between populations of the two species. Interspec
ific gene flow was indicated by the observation of occasional plants i
n sympatric populations with alleles otherwise unique to the other spe
cies. Populations of bisexual S. capillifolium were significantly more
variable than populations of unisexual S. rubellum. Alpine population
s of S. rubellum and S. capillifolium were dominated by few genotypes,
and differentiation among populations was pronounced, indicating a lo
w level of sexual recombination. In S. rubellum, maximum variability w
as found in western areas with high annual precipitation. Distribution
of alleles in S. rubellum indicated restricted gene flow between Grea
t Britain and Scandinavia. Postglacial migration from separate refugia
may explain large-scale variation in S. rubellum.