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Introgressive hybridization caused by invasive species may lead to the extinction of pure native species, but a theoretical model of the invasion process with hybridization (the neutral demographic model) suggests that introgression occurs mainly from native to invasive species. Clarifying the direction of introgression is important to evaluate the impact of hybridization on native species. In southern Japan, a widely disseminated gecko, Gekko hokouensis , and a local gecko, Gekko yakuensis , have formed mosaic hybrid zones. Given the presumed invasiveness of Gekko hokouensis , the neutral demographic model predicts that introgression would mainly occur in the direction to Gekko hokouensis , whereas possible asymmetric assortative mating suggested by a previous study predicts the opposite direction of introgression. Our investigations using microsatellite markers and mitochondrial DNA for the gecko assemblages in 12 localities and comparisons with allozyme data collected 18 years ago indicated that Gekko hokouensis expanded its range and tended to have replaced hybrids and Gekko yakuensis. Introgression was skewed towards Gekko hokouensis , but interspecific mating between the parental species was reciprocal. These results suggest that their hybridization progress follows the neutral demographic model and that the higher population growth rate of Gekko hokouensis is the major cause of species replacement, although we cannot rule out the possibility that asymmetric assortative mating also influences the later stages of species replacement. [ABSTRACT FROM AUTHOR]

Using 2010 Japanese census data, we critically interrogate the idea of integration through marriage in Japan. Intermarriage has been seen as a result of integration but the patterns of intermarriage and integration might depend on existing intersecting power structures in the receiving society. We explore assortative mating patterns in bi-national marriages in order to understand how citizenship status, race, gender, and educational level intersect and affect the patterns of intermarriage in Japan. We argue how 'integration' through bi-national marriage only perpetuates the structural hierarchy that premiers and maintain the status of the (male) native Japanese majority over Asian immigrants. [ABSTRACT FROM AUTHOR]

Due to their reduced morphology, non-photosynthetic plants have been one of the most challenging groups to delimit to species level. The mycoheterotrophic genus Monotropastrum, with the monotypic species M. humile, has been a particularly taxonomically challenging group, owing to its highly reduced vegetative and root morphology. Using integrative species delimitation, we have focused on Japanese Monotropastrum, with a special focus on an unknown taxon with rosy pink petals and sepals. We investigated its flowering phenology, morphology, molecular identity, and associated fungi. Detailed morphological investigation has indicated that it can be distinguished from M. humile by its rosy pink tepals and sepals that are generally more numerous, elliptic, and constantly appressed to the petals throughout its flowering period, and by its obscure root balls that are unified with the surrounding soil, with root tips that hardly protrude. Based on genome-wide single-nucleotide polymorphisms, molecular data has provided clear genetic differentiation between this unknown taxon and M. humile. Monotropastrum humile and this taxon are associated with different Russula lineages, even when they are sympatric. Based on this multifaceted evidence, we describe this unknown taxon as the new species M. kirishimense. Assortative mating resulting from phenological differences has likely contributed to the persistent sympatry between these two species, with distinct mycorrhizal specificity. [ABSTRACT FROM AUTHOR]

Research on educational assortative mating has devoted much attention to educational expansion but has been less focused on a concurrent trend of importance: growing differentiation among higher education institutions. In this study, I examine whether the bifurcation between high- and low-tier institutions in the context of high participation in tertiary education may clarify the mixed evidence on educational homogamy trends across countries. I apply log-linear and log-multiplicative models to analyze trends in educational assortative mating in Japan, which is characterized by a clear, widely acknowledged hierarchy of institutional selectivity. I find that the odds of homogamy are higher among graduates of selective universities than among graduates of nonselective universities. Further, assortative mating trends among graduates of selective and nonselective universities have diverged in recent years. This latter finding perhaps reflects that with the more rapid increase in the share of female students enrolled in less selective institutions, their opportunities to "marry up" have decreased. Results point to the importance of the growing heterogeneity of institutional characteristics, which was obscured in earlier studies, for understanding the impact of educational assortative mating on economic inequality. [ABSTRACT FROM AUTHOR]

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Research on educational assortative mating has devoted much attention to educational expansion but has been less focused on a concurrent trend of importance: growing differentiation among higher education institutions. In this study, I examine whether the bifurcation between high- and low-tier institutions in the context of high participation in tertiary education may clarify the mixed evidence on educational homogamy trends across countries. I apply log-linear and log-multiplicative models to analyze trends in educational assortative mating in Japan, which is characterized by a clear, widely acknowledged hierarchy of institutional selectivity. I find that the odds of homogamy are higher among graduates of selective universities than among graduates of nonselective universities. Further, assortative mating trends among graduates of selective and nonselective universities have diverged in recent years. This latter finding perhaps reflects that with the more rapid increase in the share of female students enrolled in less selective institutions, their opportunities to "marry up" have decreased. Results point to the importance of the growing heterogeneity of institutional characteristics, which was obscured in earlier studies, for understanding the impact of educational assortative mating on economic inequality., (Copyright © 2022 The Author.)

This paper estimates the extent of intergenerational income mobility in Japan among sons and daughters born between 1935 and 1975. Our estimates rely on a two-sample instrumental variables approach using representative data from the Japanese Social Stratification and Mobility surveys, collected between 1965 and 2005. Father's income is predicted on the basis of a rich set of variables, and we discuss changes in the Japanese earnings structure for cohorts born between the early 1900s and the 1960s. Our main results indicate that the intergenerational income elasticity (IGE) for both sons and daughters in Japan lies around 0.35, which is an intermediate value, by international standards. We discuss the sensitivity of the IGE to using either personal or family income as the income variable for both fathers and children. We also examine changes across cohorts in the IGE. Results indicate that intergenerational mobility has been roughly stable over the last decades. [ABSTRACT FROM AUTHOR]

We analyze the effect of a wife's human capital on her husband's earnings, using individual-level data for Japan in the period 2000-2003. We find a positive association between a wife's education and her husband's earnings, which can be attributed to the assortative mating effect as well as the positive effect of an educated wife on her husband's productivity. We divide the sample into those couples with non-working wives and those with working wives, and also employ an estimation strategy proposed by Jepsen (Review of Economics of the Household 3:197-214, ), attempting to control for the assortative mating effect. Our regression analysis provides suggestive evidence that educated wives increase their husbands' productivity and earnings only when they are non-workers and have sufficient time to support their husbands. [ABSTRACT FROM AUTHOR]