Betula apoiensis (Betulaceae), a tetraploid endemic to Mount Apoi in Hokkaido, is endangered in Japan. To reveal the origin of this species, the internal transcribed spacers and 5.8S gene of nuclear ribosomal DNA (ITS + 5.8S) and a microsatellite with its flanking region of nuclear DNA (Bp09) were sequenced and their haplotypes were determined for 12 Betula species in the Sakhalin, Hokkaido and Honshu Islands. The most parsimonious trees of ITS + 5.8S and Bp09 haplotypes had different topologies and no clades were consistent between the two trees. In both ITS + 5.8S and Bp09, B. apoiensis shared identical haplotypes with Betula ermanii and Betula ovalifolia , and had haplotypes that appeared to have been derived from each of the two species. This result suggests that B. apoiensis originated from hybridization between B. ermanii and B. ovalifolia.
To evaluate the relative importance of the factors affecting the premature abortion of acorns in Quercus serrata Thunb. ex Murray during the course of their development, inner developmental processes of acorns were observed by microscope, and applicability of the diameter of fruits (acorns with cupules) as an indicator of the inner developmental processes was discussed. Based on the observations using microscope, the developmental processes of acorns were classified into five stages; one prezygotic and four postzygotic stages (stages I to V). The diameter of sound fruits increased exponentially until 14 weeks after pollination, and the variance of diameter in each tree was fairly small (CV ϭ ~6%) during the process. Diameter of fruits can be used as a good indicator of developmental stages of acorns at individual level, and effective for the evaluation of the ecological factors affecting the premature abortion of acorns.
Three white-oak species ( Quercus crispula Blume, Quercus dentata Thunb., and Quercus serrata Thunb.) are native, widely distributed, and prominent species in the temperate deciduous forests of Japan. They are closely related to each other and overlapping morphological variation in some traits is observed, although they differ from each other in appearance. To distinguish these species genetically, we carried out clustering analysis based on Bayesian approach by AFLP markers using morphologically typical trees. Although no completely species-specific markers were obtained, these species could be distinguished and their genetic relationships were evaluated based on differences in frequencies of 66 polymorphic markers, including four that were almost completely species-specific. We also attempted to characterize putative interspecific hybrids between Q. crispula and Q. dentata sampled in a mixed stand. Two programs, HINDEX and STRUCTURE, were successfully used to detect several hybrid individuals without any prior information about their morphological traits. However, STRUCTURE and HINDEX gave conflicting indications regarding the admixture levels in some individuals.
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