On the basis of the findings of 227 surveys of Chinese fertility intentions over the years 1980-2011, this paper investigates the longitudinal changes in fertility intentions through cross-temporal meta-analysis. It i...On the basis of the findings of 227 surveys of Chinese fertility intentions over the years 1980-2011, this paper investigates the longitudinal changes in fertility intentions through cross-temporal meta-analysis. It is found that the ideal number of children for the Chinese trended downwards from 1980, but since 2000 the average number has remained basically stable at 1.6 to 1.8. In the 1980s, people＇s fertility levels were higher than their fertility intentions. With economic and educational progress in China, both fertility levels and fertility intentions showed a downward trend, with the former declining faster than the latter. Since 1990, people＇s fertility levels have been lower than their fertility intentions; that is, their actual number of children has been less than their ideal number. This provides an empirical basis for examining the changes in China＇s fertility intentions and fertility levels.展开更多
Both inter- and intrasexual selection have been implicated in the origin and maintenance of species-rich taxa with di- verse sexual traits. Simultaneous disruptive selection by female mate choice and male-male competi...Both inter- and intrasexual selection have been implicated in the origin and maintenance of species-rich taxa with di- verse sexual traits. Simultaneous disruptive selection by female mate choice and male-male competition can, in theory, lead to ~,;peciation without geographical isolation if both act on the same male trait. Female mate choice can generate discontinuities in gene flow, while male-male competition can generate negative frequency-dependent selection stabilizing the male trait polymor- phism. Speciation may be facilitated when mating preference and/or aggression bias are physically linked to the trait they operate on. We tested for genetic associations among female mating preference, male aggression bias and male coloration in the Lake Victoria cichlid Pundamilia. We crossed females from a phenotypically variable population with males from both extreme ends of the phenotype distribution in the same population （blue or red）. Male offspring of a red sire were significantly redder than males of a blue sire, indicating that intra-population variation in male coloration is heritable. We tested mating preferences of female offspring and aggression biases of male offspring using binary choice tests. There was no evidence for associations at the family level between female mating preferences and coloration of sires, but dam identity had a significant effect on female mate prefe- rence. Sons of the red sire directed significantly more aggression to red than blue males, whereas sons of the blue sire did not show any bias. There was a positive correlation among individuals between male aggression bias and body coloration, possibly due to pleiotropy or physical linkage, which could facilitate the maintenance of color polymorphism [Current Zoology 59 （2）： 221-229, 2013].展开更多
基金supported by the Social Research and Database Construction Project of CentralUniversity of Finance and Economicsthe National Social Sciences Fund(Project No.:14CRK011)
文摘On the basis of the findings of 227 surveys of Chinese fertility intentions over the years 1980-2011, this paper investigates the longitudinal changes in fertility intentions through cross-temporal meta-analysis. It is found that the ideal number of children for the Chinese trended downwards from 1980, but since 2000 the average number has remained basically stable at 1.6 to 1.8. In the 1980s, people＇s fertility levels were higher than their fertility intentions. With economic and educational progress in China, both fertility levels and fertility intentions showed a downward trend, with the former declining faster than the latter. Since 1990, people＇s fertility levels have been lower than their fertility intentions; that is, their actual number of children has been less than their ideal number. This provides an empirical basis for examining the changes in China＇s fertility intentions and fertility levels.
文摘Both inter- and intrasexual selection have been implicated in the origin and maintenance of species-rich taxa with di- verse sexual traits. Simultaneous disruptive selection by female mate choice and male-male competition can, in theory, lead to ~,;peciation without geographical isolation if both act on the same male trait. Female mate choice can generate discontinuities in gene flow, while male-male competition can generate negative frequency-dependent selection stabilizing the male trait polymor- phism. Speciation may be facilitated when mating preference and/or aggression bias are physically linked to the trait they operate on. We tested for genetic associations among female mating preference, male aggression bias and male coloration in the Lake Victoria cichlid Pundamilia. We crossed females from a phenotypically variable population with males from both extreme ends of the phenotype distribution in the same population （blue or red）. Male offspring of a red sire were significantly redder than males of a blue sire, indicating that intra-population variation in male coloration is heritable. We tested mating preferences of female offspring and aggression biases of male offspring using binary choice tests. There was no evidence for associations at the family level between female mating preferences and coloration of sires, but dam identity had a significant effect on female mate prefe- rence. Sons of the red sire directed significantly more aggression to red than blue males, whereas sons of the blue sire did not show any bias. There was a positive correlation among individuals between male aggression bias and body coloration, possibly due to pleiotropy or physical linkage, which could facilitate the maintenance of color polymorphism [Current Zoology 59 （2）： 221-229, 2013].
