Brood parasites such as the common cuckoo Cuculus canorus exploit the parental abilities of their hosts,hosts avoid brood parasitism and predation by showing specific behavior such as loss of feathers,emission of fear...Brood parasites such as the common cuckoo Cuculus canorus exploit the parental abilities of their hosts,hosts avoid brood parasitism and predation by showing specific behavior such as loss of feathers,emission of fear screams and contact calls,displaying wriggle behavior to avoid hosts or potential prey,pecking at hosts and prey,and expressing tonic immobility(showing behavior like feigning death or rapid escape from predators and brood parasites).These aspects of escape behavior are consistent for individuals but also among sites,seasons,and years.Escape behavior expressed in response to a broad range of cuckoo hosts and prey are consistently used against capture by humans,but also hosts and brood parasites and predators and their prey.An interspecific comparative phylogenetic analysis of escape behavior by hosts and their brood parasites and prey and their predators revealed evidence of consistent behavior when encountering potential parasites or predators.We hypothesize that personality axes such as those ranging from fearfulness to being bold,and from neophobic to curiosity response in brood parasites constitute important components of defense against brood parasitism that reduces the overall risk of parasitism.展开更多
We experimentally studied con-specific interference in Ibalia leucospoides, a parasitoid of the woodwasp Sirex noctilio, on pine logs containing variable numbers of woodwasp larvae. Competiton occurred when two differ...We experimentally studied con-specific interference in Ibalia leucospoides, a parasitoid of the woodwasp Sirex noctilio, on pine logs containing variable numbers of woodwasp larvae. Competiton occurred when two different-sized female parasitoids foraged on a host patch, and consequently the small female always abandoned the patch. Regardless of host density, con-specific presence did not affect the attack rate, the number of hosts attacked, nor patch residence time by the winner, when compared to a control female that foraged alone. In contrast, con-specific presence reduced patch time and the number of hosts attacked by the loser. Finally patch time （by both） as well as number of hosts attacked （by the winner only） increased with host density per patch. Our results suggest that con-specific presence has different consequences for different-sized females during patch exploitation.展开更多
Organisms often live in unpredictable environments and have to adopt life history strategies that optimize their fitness under these conditions.According to bet-hedging theory,individuals can reduce variation in fitne...Organisms often live in unpredictable environments and have to adopt life history strategies that optimize their fitness under these conditions.According to bet-hedging theory,individuals can reduce variation in fitness outcomes by investing in different strategies at the same time.For arthropods,facultative summer diapause enables survival during dry and hot periods of the year,and can be triggered by a decrease in resource abundance. However,the effect of resource depletion on diapause induction has never been disentangled from the effect of the perception of the presence of competitors.Using two solitary parasitoid species of cereal aphids as a model system,Aphidius avenae (Haliday)and Aphidius rhopalosiphi (De Stefani-Perez)(Hymenoptera:Braconidae),we tested whether (i)low absolute host density and/or (ii)high levels of parasitoid females'competition lead to maternal-induced summer diapause in parasitoid offspring.Under summer-like climatic conditions,emerging parasitoid females were (i)reared alone and exposed to different host densities (from 5 to 130 aphids),or (ii)reared together with competing females (from 2 to 20 females)and then exposed individually to 50 aphids.For both parasitoid species, low aphid densities did not induce summer diapause.However,the incidence of summer diapause increased up to a maximum of 11% with increasing levels of competition expe rienced by female parasitoids.More than 60% of the females produced both diapausing and nondiapausing offspring after being kept at the two highest competition densities. Such a "spreading-the-risk"strategy has likely evolved to optimize parasitoid fitness by preventing the following generation from exposure to low populations of suitable hosts and high mortality from superparasitism.These results provide the first experimental evidence of direct maternal competition-induced diapause in insects,and may change the way we apprehend the evolution of arthropod seasonal ecology,by considering intraspecific competition.展开更多
Based on analysis of schedule setting and player performance of the sixth CCTV host contest, we discuss the selection contest idea and point out that the good quality of thinking is the core host of outstanding qualit...Based on analysis of schedule setting and player performance of the sixth CCTV host contest, we discuss the selection contest idea and point out that the good quality of thinking is the core host of outstanding quality, and the thinking quality of excellent host has three dimensions （depth of thinking, thinking, breadth and sensitivity thinking）. Hosts should made efforts to nurture their spirituality and personality under the guidance of this scale.展开更多
本文通过对产业组织理论的掠夺定价及消耗战模型作相应的修改,加入不完全信息;并将古诺双寡头竞争模型和Fedeboger and Tirole[1]建立的“鼓鼓钱袋”模型的结合来解释跨国公司与东道国企业之间的策略性竞争行为,说明跨国公司进入发展中...本文通过对产业组织理论的掠夺定价及消耗战模型作相应的修改,加入不完全信息;并将古诺双寡头竞争模型和Fedeboger and Tirole[1]建立的“鼓鼓钱袋”模型的结合来解释跨国公司与东道国企业之间的策略性竞争行为,说明跨国公司进入发展中东道国市场的策略性行为机理,以及该策略性进入行为的发生条件。研究表明,跨国公司具有实行策略性竞争行为的强烈动机,而该行为的发生取决于跨国公司的市场分割和市场壁垒等条件。展开更多
文摘Brood parasites such as the common cuckoo Cuculus canorus exploit the parental abilities of their hosts,hosts avoid brood parasitism and predation by showing specific behavior such as loss of feathers,emission of fear screams and contact calls,displaying wriggle behavior to avoid hosts or potential prey,pecking at hosts and prey,and expressing tonic immobility(showing behavior like feigning death or rapid escape from predators and brood parasites).These aspects of escape behavior are consistent for individuals but also among sites,seasons,and years.Escape behavior expressed in response to a broad range of cuckoo hosts and prey are consistently used against capture by humans,but also hosts and brood parasites and predators and their prey.An interspecific comparative phylogenetic analysis of escape behavior by hosts and their brood parasites and prey and their predators revealed evidence of consistent behavior when encountering potential parasites or predators.We hypothesize that personality axes such as those ranging from fearfulness to being bold,and from neophobic to curiosity response in brood parasites constitute important components of defense against brood parasitism that reduces the overall risk of parasitism.
文摘We experimentally studied con-specific interference in Ibalia leucospoides, a parasitoid of the woodwasp Sirex noctilio, on pine logs containing variable numbers of woodwasp larvae. Competiton occurred when two different-sized female parasitoids foraged on a host patch, and consequently the small female always abandoned the patch. Regardless of host density, con-specific presence did not affect the attack rate, the number of hosts attacked, nor patch residence time by the winner, when compared to a control female that foraged alone. In contrast, con-specific presence reduced patch time and the number of hosts attacked by the loser. Finally patch time （by both） as well as number of hosts attacked （by the winner only） increased with host density per patch. Our results suggest that con-specific presence has different consequences for different-sized females during patch exploitation.
文摘Organisms often live in unpredictable environments and have to adopt life history strategies that optimize their fitness under these conditions.According to bet-hedging theory,individuals can reduce variation in fitness outcomes by investing in different strategies at the same time.For arthropods,facultative summer diapause enables survival during dry and hot periods of the year,and can be triggered by a decrease in resource abundance. However,the effect of resource depletion on diapause induction has never been disentangled from the effect of the perception of the presence of competitors.Using two solitary parasitoid species of cereal aphids as a model system,Aphidius avenae (Haliday)and Aphidius rhopalosiphi (De Stefani-Perez)(Hymenoptera:Braconidae),we tested whether (i)low absolute host density and/or (ii)high levels of parasitoid females'competition lead to maternal-induced summer diapause in parasitoid offspring.Under summer-like climatic conditions,emerging parasitoid females were (i)reared alone and exposed to different host densities (from 5 to 130 aphids),or (ii)reared together with competing females (from 2 to 20 females)and then exposed individually to 50 aphids.For both parasitoid species, low aphid densities did not induce summer diapause.However,the incidence of summer diapause increased up to a maximum of 11% with increasing levels of competition expe rienced by female parasitoids.More than 60% of the females produced both diapausing and nondiapausing offspring after being kept at the two highest competition densities. Such a "spreading-the-risk"strategy has likely evolved to optimize parasitoid fitness by preventing the following generation from exposure to low populations of suitable hosts and high mortality from superparasitism.These results provide the first experimental evidence of direct maternal competition-induced diapause in insects,and may change the way we apprehend the evolution of arthropod seasonal ecology,by considering intraspecific competition.
文摘Based on analysis of schedule setting and player performance of the sixth CCTV host contest, we discuss the selection contest idea and point out that the good quality of thinking is the core host of outstanding quality, and the thinking quality of excellent host has three dimensions （depth of thinking, thinking, breadth and sensitivity thinking）. Hosts should made efforts to nurture their spirituality and personality under the guidance of this scale.
文摘本文通过对产业组织理论的掠夺定价及消耗战模型作相应的修改,加入不完全信息;并将古诺双寡头竞争模型和Fedeboger and Tirole[1]建立的“鼓鼓钱袋”模型的结合来解释跨国公司与东道国企业之间的策略性竞争行为,说明跨国公司进入发展中东道国市场的策略性行为机理,以及该策略性进入行为的发生条件。研究表明,跨国公司具有实行策略性竞争行为的强烈动机,而该行为的发生取决于跨国公司的市场分割和市场壁垒等条件。
