The architecture of trees is a crucial determinant of their performance through light capture and mechanical stability. Comparison of architectural traits between closely related dioecious species is predicted to reveal both inter-specific and sexual differences. The former may reflect life-history characteristics such as microhabitat preferences, and the latter may reflect costs of reproductive allocation. We measured branching structure, leaf traits, wood density, and biomass of each vegetative component in the dioecious shrubs Lindera praecox and Lindera triloba to explore architectural differences according to species and gender. L. triloba was less branched but had a greater total leaf mass per shoot having larger and heavier leaves than L. praecox; most of these traits did not differ by gender. Allometric relationships between height and branch biomass corroborated our results of branching structure. The allometric relationships between tree size and leaf biomass demonstrated that in larger size classes females of both species had greater leaf biomass than males. Females of both species also showed lower tree height than males. This study suggests that tree architecture is influenced by both life-history strategy and resourceallocation pattern. Branching structure and branch biomass showed inter-specific differences, with the highly branched L. praecox apparently more shade tolerant than L. triloba; its tolerance is likely adaptive in its preferred microhabitat where is often lit poorly. Sexual differences in leaf biomass and tree height growth may reflect higher reproductive costs incurred by females.

The potential of long-distance pollen dispersal and the effects of small population size and population isolation on persistence of Fagus crenata populations were investigated in a small, severely isolated population (the Gofuku-ji population) and two other populations located within 7 km of this population (including 87 adult trees in total). Parentage analysis using 13 microsatellite loci showed that 94 of 100 seedlings derived from seeds collected from the Gofuku-ji population had parent pairs within this population, six had one parent within the population, and four of the six seedlings had alleles that were not detected in any of the three populations, indicating that some pollen is dispersed over distances exceeding 7 km. The estimated expected heterozygosity and effective population size were lower in the Gofuku-ji population than in previously examined large continuous populations. Therefore, levels of genetic diversity within the population may have been reduced by strong genetic drift and limitations of pollen-and seed-mediated gene flow associated with the small size and severe isolation. The contemporary mating pattern estimated at the seedling stage was biased toward outbreeding, which may be explained by possible processes: the level of inbreeding in the adult trees is increased; then, inbreeding frequently occurs but is rarely successful, while outbreeding successfully produces offspring. Additionally, high levels of significant linkage disequilibrium and higher numbers of alleles than expected under mutation-drift equilibrium from analyses of the populations' evolutionary history suggest that the Gofuku-ji population may have experienced admixture before its severe isolation. Therefore, the persistence of the Gofuku-ji population is being adversely affected by the decrease in population size and severe isolation. Further studies of gene flow via pollen in other populations with various degrees of isolation could enhance our understanding of the effects of population isolation and long-distance pollen dispersal in F. crenata and similar species.

The genus Thujopsis (Cupressaceae) comprises monoecious coniferous trees endemic to Japan. This genus includes two varieties: Thujopsis dolabrata (L.f.) Siebold et Zucc. var. dolabrata (southern variety, Td) and Thujopsis dolabrata (L.f.) Siebold et Zucc. var. hondae Makino (northern variety, Th). The aim of this study is to understand the phylogeographic and genetic population relationships of the genus Thujopsis for the conservation of genetic resources and future breeding. A total of 609 trees from 22 populations were sampled, including six populations from the Td distribution range and 16 populations from the Th distribution range. The genotyping results for 19 expressed sequence tag (EST)-based simple sequence repeat (SSR) markers, followed by a structure analysis, neighbor-joining tree creation, an analysis of molecular variance (AMOVA), and hierarchical F statistics, supported the existence of two genetic clusters related to the distribution regions of the Td and Th varieties. The two variants, Td and Th, could be defined by their provenance, in spite of the ambiguous morphological differences between the varieties. The distribution ranges of both variants, which have been defined from their morphology, was confirmed by genetic analysis. The Th populations exhibited relatively uniform genetic diversity, most likely because Th refugia in the glacial period were scattered throughout their current distribution area. On the other hand, there was a tendency for Td’s genetic diversity to decrease from central to southern Honshu island. Notably, the structure analysis and neighbor-joining tree suggest the hybridization of the two varieties in the contact zone. More detailed studies of the genetic structure of Td are required in future analyses.