Males of the nursery web spider Pisaura mirabil usually offer an insect prey wrapped in white silk as a nuptial gift to facilitate copulation. Males exploit female foraging preferences in a sexual context as females f...Males of the nursery web spider Pisaura mirabil usually offer an insect prey wrapped in white silk as a nuptial gift to facilitate copulation. Males exploit female foraging preferences in a sexual context as females feed on the gift during copula- tion. It is possible for males to copulate without a gift, however strong female preference for the gift leads to dramatically higher mating success for gift-giving males. Females are polyandrous, and gift-giving males achieve higher mating success, longer copulations, and increased sperm transfer that confer advantages in sperm competition. Intriguingly, field studies show that ap- proximately one third of males carry a worthless gift consisting of dry and empty insect exoskeletons or plant fragments wrapped in white silk. Silk wrapping disguises gift content and females are able to disclose gift content only after accepting and feeding on the gift, meanwhile males succeed in transferring sperm. The evolution of deceit by worthless gift donation may be favoured by strong intra-sexual competition and costs of gift-construction including prey capture, lost foraging opportunities and investment in silk wrapping. Females that receive empty worthless gifts terminate copulation sooner, which reduces sperm transfer and likely disadvantages males in sperm competition. The gift-giving trait may thus become a target of sexually antagonistic co-evolution, where deceit by worthless gifts leads to female resistance to the trait. We discuss factors such as female mating rate and intensity of sperm competition that may shape the evolution of male deception, and how ecological factors may influence the evolution and maintenance of worthless gifts as an evolutionarily stable alternative mating strategy by frequency dependent selection展开更多
The Industrial Clusters show more competitive advantage in the world obviously since 1970＇s, which attracts extensive attention from all over the world. As the most important researches of the New Economic Geography,...The Industrial Clusters show more competitive advantage in the world obviously since 1970＇s, which attracts extensive attention from all over the world. As the most important researches of the New Economic Geography, Poter＇s diamond model generalizes the internal mechanism of clusters, but the model has not given the microcosmic status of the factors of the clusters, therefore, it is significant to go deeper into the diamond model and the dissertation wishes to do some researches deeply.Based on the actuality of research, this paper surveys Porter＇s diamond model from the Evolutionary Economics, and combines the research of the field with the instance in China, then puts forward the diamond model of twin-screw and implements the model into traditional industrial clusters in Zheiiang province. Detailed explaining is as follows. The main innovations of the dissertation are as follows： （1） having taken the points of biology into economics, and developing the Evolutionary Economics creatively; （2） having proved the diamond model, put forward a twin-screw microcosmic model for the first time, and tried to study the dynamic and solid relationships of each factor in the diamond model, which is the most important innovation of the dissertation.展开更多
文摘Males of the nursery web spider Pisaura mirabil usually offer an insect prey wrapped in white silk as a nuptial gift to facilitate copulation. Males exploit female foraging preferences in a sexual context as females feed on the gift during copula- tion. It is possible for males to copulate without a gift, however strong female preference for the gift leads to dramatically higher mating success for gift-giving males. Females are polyandrous, and gift-giving males achieve higher mating success, longer copulations, and increased sperm transfer that confer advantages in sperm competition. Intriguingly, field studies show that ap- proximately one third of males carry a worthless gift consisting of dry and empty insect exoskeletons or plant fragments wrapped in white silk. Silk wrapping disguises gift content and females are able to disclose gift content only after accepting and feeding on the gift, meanwhile males succeed in transferring sperm. The evolution of deceit by worthless gift donation may be favoured by strong intra-sexual competition and costs of gift-construction including prey capture, lost foraging opportunities and investment in silk wrapping. Females that receive empty worthless gifts terminate copulation sooner, which reduces sperm transfer and likely disadvantages males in sperm competition. The gift-giving trait may thus become a target of sexually antagonistic co-evolution, where deceit by worthless gifts leads to female resistance to the trait. We discuss factors such as female mating rate and intensity of sperm competition that may shape the evolution of male deception, and how ecological factors may influence the evolution and maintenance of worthless gifts as an evolutionarily stable alternative mating strategy by frequency dependent selection
文摘The Industrial Clusters show more competitive advantage in the world obviously since 1970＇s, which attracts extensive attention from all over the world. As the most important researches of the New Economic Geography, Poter＇s diamond model generalizes the internal mechanism of clusters, but the model has not given the microcosmic status of the factors of the clusters, therefore, it is significant to go deeper into the diamond model and the dissertation wishes to do some researches deeply.Based on the actuality of research, this paper surveys Porter＇s diamond model from the Evolutionary Economics, and combines the research of the field with the instance in China, then puts forward the diamond model of twin-screw and implements the model into traditional industrial clusters in Zheiiang province. Detailed explaining is as follows. The main innovations of the dissertation are as follows： （1） having taken the points of biology into economics, and developing the Evolutionary Economics creatively; （2） having proved the diamond model, put forward a twin-screw microcosmic model for the first time, and tried to study the dynamic and solid relationships of each factor in the diamond model, which is the most important innovation of the dissertation.
