The early stage of volcanic desert succession is underway on the southeastern slope of Mount Fuji. We used markers of nuclear microsatellites (simple sequence repeats; SSR) and chloroplast microsatellites (cpSSR) to investigate the population genetic structure and reproduction dynamics of Salix reinii, one of the dominant pioneer shrubs in this area. The number of S. reinii genets in a patch and the area of the largest genet within the patch increased with patch area, suggesting that both clonal growth and seedling recruitment are involved in the reproduction dynamics of S. reinii. Five polymorphic cpSSR markers were developed for S. reinii by sequencing the noncoding regions between universal sequences in the chloroplast genome. Nineteen different cpSSR haplotypes were identified, indicating that S. reinii pioneer genets were created by the long-distance dispersal of seeds originating from different mother genets around the study site, where all vegetation was destroyed during the last eruption. Furthermore, the clustered distributions of different haplotypes within each patch or plot suggested that newly colonized genets tended to be generated from seeds dispersed near the initially established mother genets. These results revealed that the establishment of the S. reinii population on the southeastern slope of Mount Fuji involved two sequential modes of seed dispersal: long-distance dispersal followed by short-distance dispersal.

Robinia pseudoacacia L. is a clonal tree species. To investigate a mutation within eight microsatellite loci of R. pseudoacacia, we analyzed DNA samples obtained from different leaf samples within each ramet, leaves from ramets within the genet, and seeds. Of the eight loci, locus Rops15 (AG motif) displayed hypermutability. The mutation rates of Rops15 within each ramet, among ramets within the genet, and offspring were 6.27% (ranging from 0 to 31.1%), 6.11% (from 0 to 25.0%) and 3.78% (from 0 to 10.9%), respectively. The mutation rate increased with allele size (13-71 repeat units). The mutation patterns observed in Rops15 were distinctive in two ways. First, there was a significant bias toward additions over deletions, and both addition and deletion of single repeats were dominant at alleles with lengths less than 232 bp (63 repeats). Second, for the longest allele of 248 bp (71 repeats), the number of losses was higher than the number of gains. These observations suggest that the mutation patterns of microsatellites in R. pseudoacacia may follow a generalized stepwise mutation model, and that the tendency of long alleles to mutate to shorter lengths acts to prevent infinite growth. Finally, the observation of somatic hypermutability at locus Rops15 highlights the need for caution when using highly polymorphic microsatellites for population genetic structure and paternity analysis in tree species.

Bacterial communities inhabiting the rhizosphere of Lepironia articulata (reedgrass) grown in a strongly acidic sulfate soil distributed in the province of Narathiwat, Thailand were investigated. Fresh roots of L, articulata were cut from the subterranean stem, and the bacteria were isolated from the homogenate on dilution plates of glucose-yeast extract agar medium adjusted to pH 4.5. In or on the roots, 3.3x107 bacteria(cfu) g-1 fresh roots were present. From the dilution plates, 60 bacteria were randomly isolated and their characteristics were examined. All the isolates were Gram-negative rods and grew well at pH 4.5. Analysis of cell fatty acids and the restriction fragment length polymorphism (RFLP) of PCR-amplified 16S rRNA genes indicated that the isolates could be divided into 4 groups (Group I to IV). Group I (65% of total) isolates failed to grow on the agar plate at pH 7. The sequence analysis of 16S rRNA genes of a Group I isolate showed that it resembled Acidocella facilis with 98.5% homology. Growth of Group I bacteria was suppressed by acetate. The next most abundant bacteria, belonging to Group II, grew at pH 7.0 and belonged to Burkholderia. These bacteria accounted for 28% of all the isolates. Bacteria of Group III and IV (identified as Bacillus subtilis) were a minor constituent only. Group III isolates were similar to the genus Xanthomonas, but the similarity of the 16S rRNA gene base arrangement with the nearest species was below 90%.