High levels of genetic variation in the haploid leafy liverwort Porella platyphylla from the southeastern United States

The few studies that have investigated levels of genetic variation in liverworts have found very little polymorphism. Our electrophoretic data show, however, that the leafy liverwort Porella platyphylla maintains high levels of genetic variation in at least some natural populations from the southeastern United States. Within a single population from southwestern North Carolina, we detected 26 distinct multilocus genotypes and more than 80% of the enzyme loci we surveyed were polymorphic. It seems likely that earlier studies of mostly thalloid species from glaciated regions of Europe have presented a biased picture of levels of variation in liverwort populations

Identyfing alien genotypes and their consequences for genetic variationin clonal seed orchards of Pinus sylvestris L.

This study investigates the rates of grafting and planting errors that occur in seed orchards, and evaluates their effects on the genetic diversity and relatedness of genotypes. The study used three clonal Scots pine seed orchards of differing ages and clonal composition located in the forest districts of Susz, Pniewy and Zdrojowa Góra, Poland. Maximum breeding ability within a seed orchard requires isolated from external sources of pollen, and have no alien genotypes inside the orchard. We used 13 isoenzyme markers to determine the genotypic identity of ramets and compared the number of genotypes of the actual current ramet population (W1) with genotypes comprising the originally intended plus trees (designated as W0) to estimate the genotypic assignment error rate per orchard. For both W0 and W1, we calculated the effective number of clones and the relative effective number of clones. Ramet assignment errors were detected in all three seed orchards. Gnotypic errors ranged from 5.8% to 37.7% across orchards. A total of 46 alleles were found, with the mean number of alleles per locus ranging from 2.77 to 3.23. At individual loci, the level of observed heterozygosity was variable. Alien genotypes had negligible effects on seed orchard heterozygosity. The Fst values between seed orchards amounted to 0.6% between Susz and Pniewy and 1.1% between Susz and Zdrojowa Góra. The effect on genetic variation of ramet assignment errors was small and influenced genetic diversity only in the case of the Susz seed orchard. However, our results suggest that negative effects of alien genotypes can occur on breeding value of seeds from analysed seeds orchards

Clonal distribution, fertility and sex ratios of the moss Plagiomnium affine (Bland.) T.Kop. in forests of contrasting age

Six populations of the clonal forest floor moss Plagiomnium affine from forests of different age were screened for genetic variation at 23 allozyme loci, of which nine were polymorphic. Samples consisting of two adjacent unconnected shoots were taken at regular intervals along one transect from each population. A total of 602 shoots was analysed. Almost 80% of the shoots were sterile (i.e. not expressing male or female gender). Sex remained unknown for only 10% of shoots after identification of genets based on electrophoretic data. We identified a mean number of 3.7 fertile clones per population. The mean length of clones along transects in each population ranged between 2 and 3 in. The size distribution within populations was bimodal, with a few dominant clones and a varying number of much smaller clones. The overall sex ratio was slightly female biased at the ramet level, but balanced at the genet level. Forest age was negatively correlated with percentage of sterile shoots and positively correlated with frequency of sporophytes. In both cases correlations were significant only if population 1, which was subject to extreme soil disturbance by badgers, was excluded. We conclude that the effective population size is larger, and the susceptibility to genetic drift is lower, in old forests