Collections from 31 populations of A. barbata from diverse habitats in Israel were assayed electrophoretically for seven enzyme systems. Phenotype frequencies were scored in nine enzyme zones, probably representing 27 loci, to determine isozyme variability within and among populations. Many different isozyme phenotypes were found in all of the populations; also the array of isozyme phenotypes found in each population differed distinctly from that found in each other population. Overlays of phenotypic frequencies on map locations showed that isozyme variability is distributed in mosaic patterns not related to geographical distance. Principal-component and multiple-regression analyses revealed that temperature and moisture-related variables are significantly correlated with particular isozyme phenotypes. Further, the mosaic patterns of isozyme variation were found to correspond closely to mosaic patterns of the habitat. This structuring of the genetic variability into multilocus combinations was attributed to the combined effects of directional and diversifying selection. Comparisons of patterns and extent of genetic variation in Israel and California led to the conclusion that the evolution of 'ecotypes,' each adapted to a specific habitat and marked by a particular set of enzyme alleles, has proceeded further in Israel, where A. barbata is endemic, than in California, where it is a recent introduction.

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Dormant buds of individual Sorbus torminalis trees collected from eight Polish populations were tested with horizontal gel electrophoresis according to one locus of PGI enzyme system. Three allozymes of different frequency were identified in each population. Genetic variability based on PGI locus A was high within seven populations (mean Ho=0.602 and mean Pg=0.491). Only one population with A3A3 genotypes was monomorphic, most probably due to intensive vegetative propagation or founder effect. The level of genetic differences among populations based on one variable locus reached GST=0.13

Genetic variation of twelve Polish populations of Primula veris L. from western Poland was investigated in respect of six enzyme systems: 6-phosphogluconate dehydrogenase (6PGD), diaphorase (DIA), menadione reductase (MNR), formate dehydrogenase (FDH), isocitrate dehydrogenase (IDH) and glutamate oxaloacetate transaminase (GOT). Only two of them (6PGD and DIA) were polymorphic and all populations were compared according to four loci and eight alleles. For 6PGD only one out of the two detected loci (locus 6PGD-2) was polymorphic and consisted of three alleles a, b and c. For DIA each of two detected loci had two alleles. For 6PGD-2 one population was monomorphic and four populations were monomorphic for DIA-1 and DIA-2. The rest of the populations were polymorphic with low frequency of heterozygotes. The low heterozygosity level, found in the examined populations, was confirmed by high values of the fixation index (F). The level of genetic differentiation among GST populations specified for each polymorphic loci, was equal to 0.045 for 6PGD-2 and had the value of 0.078 for DIA-2 and 0.186 for DIA-1. Nm value for polymorphic loci was 1.10 for DIA-1 and 2.94 for DIA-2, and for 6PGD-2 was 5.33, what indicates some gene flow between the examined populations. The dendrogram constructed on the basis of genotype frequencies showed that the populations were divided into two groups, however the most southern population No. 2 was clearly similar to the northern population No. 8

Plant material from 42 common reed populations originating from various lakes and ponds in northwest Poland were investigated with respect to eight panicle traits and three peroxidase loci that were detected with electrophoresis. Genetic differences between populations were estimated based on allozyme frequencies. Electrophoretic data indicated that some populations contain an excess of heterozygotes, pointing to extensive gene flow, which is typical of panmictic, openpollinated populations.