Mid Sweden University

The mode of inheritance of six enzyme markers in the octoploid alpine plant Cerastium alpinum was analyzed. Offspring from crosses between heterozygotes showed fixed heterozygosity at malate dehydrogenase-2, phosphoglucoisomerase-2, triosephosphate isomerase-2, and triosephosphate isomerase-3. Phosphoglucomutase-1 also showed fixed heterozygosity except in offspring from one cross. Fixed heterozygosity in five enzyme systems suggests that C. alpinum has originated through at least some allopolyploidization. Offspring from plants heterozygous for two alleles at the menadione reductase-1 (Mr-1) locus did not deviate significantly from a 1:2:1 ratio. The large proportion of homozygotes suggests disomic inheritance because any kind of polysomic inheritance would result in a substantially increased proportion of heterozygotes relative to disomic inheritance. Assuming a diploid model for Mr-1, this locus was used to analyze the population genetic structure within C. alpinum populations. Inbreeding was found in many alpine populations. This may help explain the large genetic distances found among alpine populations in a previous study. The analysis is only based on one segregating locus, and the results should therefore be treated with caution. However, by establishing the mode of inheritance through crosses, we have been able to use a codominant marker in population genetic analysis of an octoploid plant.

The effects of Ni and Mg, two factors involved in the infertility of serpentine soils, were studied in the alpine plant Cerastium alpinum. Root growth of plants from adjacent serpentine and non-serpentine populations in Scandinavia, representing an eastern and western postglacial immigration lineage and the hybrid zone between them, were compared to study the adaptation of C. alpinum populations. • Seedlings were placed in solutions with low or high concentrations of Ni and Mg in a full factorial experiment according to a randomized block design. The growth of roots was analyzed and discussed in relation to the soil content. • The serpentine populations showed higher tolerance to Ni and Mg stress than non-serpentine populations. The degree of metal tolerance differed among the serpentine populations and was related to the effective concentrations of Ni and Mg in the soil at each site. • The results suggest that serpentine tolerance is locally evolved in C. alpinum and that tolerance has arisen in parallel during the postglacial colonization of Scandinavia on serpentine soils with similar composition.

The most common and widespread alpine plants on ultramafic soils in Fennoscandia belong to the Cerastium alpinum complex (Caryophyllaceae). This complex consists of polyploid alpine plants, which show great morphological variation. Both hairy and glabrous morphotypes are found on ultramafic soils. To shed light on the evolution and the postglacial colonization of the C. alpinum complex, we have studied the genetic differentiation of populations on ultramafic soils in Fennoscandia. Thirteen populations in Norway, Sweden and Finland were analysed by starch gel enzyme electrophoresis. Preliminary results show that there is a genetic and geographical differentiation of populations on ultramafic soils, resulting in one eastern and one western group. This suggests that there were two independent postglacial colonization events of C. alpinum on ultramafic soils in Fennoscandia. The hairy and glabrous morphotypes are found both in the eastern and western population groups, suggesting that the morphotypes on ultramafic soils have a multiple origin.

The plant cover of Fennoscandia is young because of the recent glaciation. This study covers the early stages of diversification and the genetic consequences of postglacial migration of a hermaphroditic polyploid plant, Cerastium alpinum. It has a continuous distribution in the alpine region, where it grows on alpine heaths and serpentine soils that are rich in heavy metals. Within the boreal forest C. alpinum has a scattered distribution on serpentine, dolomite and steep slopes. Plants from 31 populations in Norway, Sweden and Finland were subjected to enzyme electrophoresis. Analyses of the enzyme phenotypes suggest that C. alpinum has colonized Fennoscandia through two postglacial immigration events resulting in a southeastern and a southwestern lineage. These two lineages seem to meet in a hybrid zone in northern Sweden. Large genetic differences were found among most populations in both the southeastern and the southwestern lineages. This suggests that the populations are effectively isolated from each other.