Demographic genetics of the American beech, Fagus grandifolia. II. Genet substructure of populations for the Blue Ridge, Piedmont and the Great Smoky Mountains

Populations of American beech in Virginia and the Great Smoky Mountain National Park in Tennessee and North Carolina were investigated for demographic genetic substructurings. Two Virginia populations, one on the Blue Ridge (WG1) and the other on the Piedmont (WG2) occur over an elevational gradient of several hundreds meters. One of the Great Smoky Mountain populations (GS1) was in a 'beech gap' and the other (GS2) in a 'cove forest' along a creek. The populations in the Great Smoky Mountain National Park were only separated by a few hundred meters in elevation, but both on the same physiographic province. The populations had two growth forms. Trees produced extensive root suckers at WG1, GS1 and GS2, but WG2 had no root suckers and all individuals had obviously been established from seeds. A total of 1335 shoots were mapped at the four sites, their size measured [diameter at breast height (DBH) or diameter at ground height (DGH)], and genotypes were determined for each locus using allozyme analysis. F_IS among five different size-classes revealed an excess of homozygotes in WG1, GS1 and GS2, and an excess of heterozygotes in WG2. The offshoot formation from root suckers obviously contributed to the abundance of intermediate size-classes in WG1, GS1 and GS2. Exceedingly localized patchiness of different multilocus genotypes reveals genetic clustering of shoots that have obviously originated from root suckers in WG1, GS1 and GS2. The Piedmont population (WG2), on the other hand, showed loose localization of genetically related trees at a scale of 35–40 m in area, suggesting broader ranges of pollen and seed dispersal. The data are discussed in the light of the differences in growth form and mode of reproduction, and also in relation to the post-glacial migration and the current geographic distribution of the species.     

Molecular cloning and characterization of the AVR-Pia locus from a Japanese field isolate of Magnaporthe oryzae

In order to clone and analyse the avirulence gene AVR-Pia from Japanese field isolates of Magnaporthe oryzae , a mutant of the M. oryzae strain Ina168 was isolated. This mutant, which was named Ina168m95-1, gained virulence towards the rice cultivar Aichi-asahi, which contains the resistance gene Pia. A DNA fragment (named PM01) that was deleted in the mutant and that co-segregated with avirulence towards Aichi-asahi was isolated. Three cosmid clones that included the regions that flanked PM01 were isolated from a genomic DNA library. One of these clones (46F3) complemented the mutant phenotype, which indicated clearly that this clone contained the avirulence gene AVR-Pia . Clone 46F3 contained insertions of transposable elements. The 46F3 insert was divided into fragments I–VI, and these were cloned individually into a hygromycin-resistant vector for the transformation of the mutant Ina168m95-1. An inoculation assay of the transformants revealed that fragment V (3.5 kb) contained AVR-Pia . By deletion analysis of fragment V, AVR-Pia was localized to an 1199-bp DNA fragment, which included a 255-bp open reading frame with weak homology to a bacterial cytochrome- c -like protein. Restriction fragment length polymorphism analysis of this region revealed that this DNA sequence co-segregated with the AVR-Pia locus in a genetic map that was constructed using Chinese isolates.     

Strategies for the conservation and management of isolated salmonid populations: lessons from Japanese streams

1. Endangered native populations of stream salmonids in Japan face three major threats: (i) negative interactions with introduced hatchery‐reared fish, (ii) fragmentation of habitat by impassable dams and (iii) recreational angling. 2. To prevent imminent extinction of many local populations, we evaluated these threats and possible conservation actions for red‐spotted masu salmon (Oncorhynchus masou ishikawae) and white‐spotted charr (Salvelinus leucomaenis japonicus) in the Fuji River system in central Japan. 3. Red‐spotted masu salmon and white‐spotted charr occupied only 0.73 and 2.4% of suitable thermal habitats, respectively, with masu salmon typically occupying habitats closer to human population centres. 4. Population viability analysis resulted in a 100‐year probability of extinction of 78.1% for masu salmon and 48.1% for charr. However, extinction risk of both species was predicted to be <5% if the carrying capacity increased from 141 to 303 for masu salmon and from 94 to 125 for charr, by allowing fish passage at the lower end of the habitat, and if annual adult survival rate increased by 0.04. Adult survival rate was the principal factor associated with population persistence. 5. To conserve isolated populations of stream‐dwelling salmonids, we recommend (i) assessing the distribution of remnant native and non‐native fish populations, (ii) that fishing regulations are modified to improve adult survival and population persistence and (iii) that fragmented reaches be reconnected to adjacent habitat, for example by removing or modifying artificial barriers to increase the carrying capacity of the isolated populations. Reconnection of fragmented reaches should, however, be avoided if it results in non‐native fish invading isolated populations.