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Differences in demographic history, life-history traits, and breeding systems affect nucleotide variation patterns. It is expected that shade-intolerant pioneer tree species have different patterns of genetic polymorphism and population structure than climax species. We studied patterns of nucleotide polymorphism at four putative starch pathway loci (agpSA, agpSB, agpL, and GBSSI) in Zanthoxylum ailanthoides, a shade-intolerant pioneer tree species that occupies forest gaps in warm-temperate forests of East Asia. Genetic diversity was lower within each population than among populations, and differentiation among populations was high across the loci (F(ST) = 0.32-0.64), as expected from the insect-pollinated breeding system and the metapopulation structure of this pioneer species. Numbers of haplotypes were smaller than those expected from the observed numbers of segregating sites. Single haplotypes accounted for more than 47% of all the sampled genes at the respective loci. These variation patterns were incompatible with neutral predictions for populations of a finite island model. Complex population dynamics, such as bottleneck and/or admixture, in the history of this pioneer tree species might have resulted in the observed patterns of genetic variation and population structure, which are different from those of climax wind-pollinated tree species, such as conifers. In contrast to the other loci investigated in this study, agpL showed nearly no variation in Z. ailanthoides (one singleton only), but there was some extent of variation in a closely related species, Zanthoxylum schinifolium. This suggests possibly a recent selective sweep at or near the locus in Z. ailanthoides.

For elucidation of the taxonomic status of the Japanese Fasciola species, whole mitochondrial DNA of Fasciola hepatica from Australia, F. gigantica from Malaysia, and Fasciola sp. from Japan was digested with three four-base-cutting endonucleases: HinfI, MspI, and RsaI. The resulting digestion patterns showed that for each enzyme there were some bands specific for each geographical isolate and that the Japanese Fasciola sp. shared more bands with F. gigantica than with F. hepatica. Nucleotide sequences of two regions, the second internal transcribed spacer (ITS2) of the nuclear ribosomal RNA cluster and mitochondrial cytochrome c oxidase subunit I (COI), were also compared among them. The ITS2 sequence was highly conserved among the three isolates. F. gigantica and the Japanese Fasciola sp. were identical, but they differed from the Australian F. hepatica at six sites, one of which was a deletion. The COI sequence was less conserved but implied a similar relationship between the isolates. There seems no reason to regard the Japanese Fasciola sp. as anything other than a strain of F. gigantica.

Age changes in the livers of Costa Ricans have been compared with those of native and Hawaii Japanese and U.S. caucasians. In the case of the U.S. caucasians and Costa Ricans, the decrease in the number of hepatic cells is similar up to 70 years of age, but after 80 years of age the decrease is more marked in the Costa Ricans. The difference in the process of senile change among these four groups suggests that the environmental, especially nutritional, conditions during their childhood and adolescence play an important role.

Age changes in the liver of the Hawaii-Japanese have been compared with those of native Japanese and Caucasians in the United States. Among the Japanese in Hawaii, all cases over 70 years of age were migrant Japanese to Hawaii, i.e. Issei, those under 60 years of age were their Hawaii born descendents, i.e. Nisei, and cases in the 7th decade were composed of Nisei and Issei. Aging changes of the liver seem to begin earlier in the Nisei and Caucasians than in the native Japanese. The earlier onset of aging can be explained on the basis of earlier maturation due to better nutritional conditions. The marked decrease in the number of hepatic cells in the Issei may well be a reflection of their nutritional state during their early years. They, in this sense, resemble the native Japanese.