In Europe, eggs of the Common Cuckoo (Cuculus canorus) have been found in more than 125 different host species. However, very few species are frequently parasitized. The Cuckoo is divided into several distinct races t...In Europe, eggs of the Common Cuckoo (Cuculus canorus) have been found in more than 125 different host species. However, very few species are frequently parasitized. The Cuckoo is divided into several distinct races termed gentes. Females of each gens specialize in parasitizing a particular host species. More than 20 such gentes are recognized in Europe. Each female Cuckoo lays eggs of constant appearance. Most gentes can be separated based on their distinct egg types, which in many cases mimic those of their hosts. Different gentes may occur in sympatry or may be separated geographically. Some gentes may occur in restricted parts of the host’s distribution area. These patterns raise some fundamental questions like: Why are some passerine species preferred as hosts while others are not? Why does a host population consist of individuals either accepting or rejecting Cuckoo eggs? Why is there marked variation in egg rejection behavior between various host populations? How distinct and host-specialized are Cuckoo gentes? These questions are discussed in relation to existing knowledge and future perspectives.展开更多
e coevolutionary arms race between cuckoos and their hosts predicts that low variation in egg features within a host clutch would facilitate discrimination of mimetic parasite eggs.Here,we experimentally examine this ...e coevolutionary arms race between cuckoos and their hosts predicts that low variation in egg features within a host clutch would facilitate discrimination of mimetic parasite eggs.Here,we experimentally examine this prediction by using arti cial and natural parasite eggs showing contrasting level of matching with host eggs.We quanti ed,based on human assessment,intra-clutch variation in egg appearance and egg discrimination in the Iberian Azure-winged Magpie(Cyanopica cyanus),a presumed former host of the Great Spotted Cuckoo(Clamator glandarius).Azure-winged Magpies rejected parasitic eggs in relation to their degree of dissimilarity with own eggs:Great Spotted Cuckoo model eggs were relatively more o en rejected(73.7%) than real Great Spotted Cuckoo eggs(44.4%) and the less contrasting conspeci c eggs(35.5%).Contrary to our predictions,we found that,irrespective of mimicry level of parasitic eggs,intra-clutch variation in host egg appearance did not di er signi cantly between rejecters and acceptors.We found,however,that individuals with higher variation in egg-size were almost signi cantly more prone to be rejecters than individuals showing lower variation in egg size.Our results do not support the hypothesis that the extent of intraclutch variation in egg discrimination varied with parasite egg mimicry in this particular system,and add to previous ndings suggesting that perhaps an increase in intra-clutch variation in egg appearance,rather than a decrease,might be advantageous when discriminating against non-mimetic Great Spotted Cuckoo eggs.展开更多
Historically Turks had always relied on military power. The culture is rich with martial values to this day. Even each civilian is somewhat soldierly in a sense, in general. Nevertheless, in a more detailed analysis, ...Historically Turks had always relied on military power. The culture is rich with martial values to this day. Even each civilian is somewhat soldierly in a sense, in general. Nevertheless, in a more detailed analysis, in some territories of the country, the prestige enjoyed by the military is more intensive than the average, while in some other territories, respect for military people is much below the average tendency. One might infer that in the former category, it is a question of the regions where the inhabitants are mild, soft-spoken, and compatible. They accordingly admire discipline and display obedient attitudes vis-a-vis governmental authority ever since the Ottoman times, merely as a cultural and traditional trait. Those regions are certainly places where military people today are held in high esteem. In such locations, even the ideal profession for a little boy is indoctrinated as a military career, by the whole family or the surrounding social environment. It should be mentioned that in certain cities and towns, a substantial percentage of the population are represented by immigrants, who got re-patriated along the course of the near history, as the former Ottoman Empire began shrinking in territory due to loss of land, during successive wars. The crushing majority of the Muslim Ottoman subjects in those lost territories preferred leaving their property and escaping into the Anatolian mainland, rather than renouncing their belief and assimilating to the new political regime. Having suffered at the hands of foreign powers, those people have also been especially appreciative of the value of their own soldiers. As for the latter category, dislike of discipline and authority can be mainly attributed to the special social structure and historical circumstances.展开更多
Sexual deception involves the mimicry of another species＇ sexual signals in order to exploit behavioural routines linked to those signals. Known sexually deceptive systems use visual, acoustic or olfactory mimicry to...Sexual deception involves the mimicry of another species＇ sexual signals in order to exploit behavioural routines linked to those signals. Known sexually deceptive systems use visual, acoustic or olfactory mimicry to exploit insects for preda- tion, cleptoparasitism and pollination. It is predicted that where sexual deception inflicts a cost on the receiver, a coevolutionary arms race could result in the evolution of discriminating receivers and increasingly refined mimicry. We constructed a conceptual model to understand the importance of trade-offs in the coevolution of sexually deceptive mimic and receiver. Four components examined were： the cost of mimicry, the cost to receiver for being fooled, the density of mimics and the relative magnitude of a mimicry-independent component of fitness. The model predicts that the exploitation of non-discriminating receivers by accurate signal mimicry will evolve as an evolutionary stable strategy under a wide range of the parameter space explored. This is due to the difficulty in minimising the costs of being fooled without incurring the cost of falsely rejecting real mating opportunities. In the model, the evolution of deception is impeded when mimicry imposes substantial costs for both sides of the arms race. Olfac- tory signals that are potentially cheap to produce are therefore likely to be more vulnerable to exploitation than expensive visual ornaments展开更多
文摘In Europe, eggs of the Common Cuckoo (Cuculus canorus) have been found in more than 125 different host species. However, very few species are frequently parasitized. The Cuckoo is divided into several distinct races termed gentes. Females of each gens specialize in parasitizing a particular host species. More than 20 such gentes are recognized in Europe. Each female Cuckoo lays eggs of constant appearance. Most gentes can be separated based on their distinct egg types, which in many cases mimic those of their hosts. Different gentes may occur in sympatry or may be separated geographically. Some gentes may occur in restricted parts of the host’s distribution area. These patterns raise some fundamental questions like: Why are some passerine species preferred as hosts while others are not? Why does a host population consist of individuals either accepting or rejecting Cuckoo eggs? Why is there marked variation in egg rejection behavior between various host populations? How distinct and host-specialized are Cuckoo gentes? These questions are discussed in relation to existing knowledge and future perspectives.
文摘e coevolutionary arms race between cuckoos and their hosts predicts that low variation in egg features within a host clutch would facilitate discrimination of mimetic parasite eggs.Here,we experimentally examine this prediction by using arti cial and natural parasite eggs showing contrasting level of matching with host eggs.We quanti ed,based on human assessment,intra-clutch variation in egg appearance and egg discrimination in the Iberian Azure-winged Magpie(Cyanopica cyanus),a presumed former host of the Great Spotted Cuckoo(Clamator glandarius).Azure-winged Magpies rejected parasitic eggs in relation to their degree of dissimilarity with own eggs:Great Spotted Cuckoo model eggs were relatively more o en rejected(73.7%) than real Great Spotted Cuckoo eggs(44.4%) and the less contrasting conspeci c eggs(35.5%).Contrary to our predictions,we found that,irrespective of mimicry level of parasitic eggs,intra-clutch variation in host egg appearance did not di er signi cantly between rejecters and acceptors.We found,however,that individuals with higher variation in egg-size were almost signi cantly more prone to be rejecters than individuals showing lower variation in egg size.Our results do not support the hypothesis that the extent of intraclutch variation in egg discrimination varied with parasite egg mimicry in this particular system,and add to previous ndings suggesting that perhaps an increase in intra-clutch variation in egg appearance,rather than a decrease,might be advantageous when discriminating against non-mimetic Great Spotted Cuckoo eggs.
文摘Historically Turks had always relied on military power. The culture is rich with martial values to this day. Even each civilian is somewhat soldierly in a sense, in general. Nevertheless, in a more detailed analysis, in some territories of the country, the prestige enjoyed by the military is more intensive than the average, while in some other territories, respect for military people is much below the average tendency. One might infer that in the former category, it is a question of the regions where the inhabitants are mild, soft-spoken, and compatible. They accordingly admire discipline and display obedient attitudes vis-a-vis governmental authority ever since the Ottoman times, merely as a cultural and traditional trait. Those regions are certainly places where military people today are held in high esteem. In such locations, even the ideal profession for a little boy is indoctrinated as a military career, by the whole family or the surrounding social environment. It should be mentioned that in certain cities and towns, a substantial percentage of the population are represented by immigrants, who got re-patriated along the course of the near history, as the former Ottoman Empire began shrinking in territory due to loss of land, during successive wars. The crushing majority of the Muslim Ottoman subjects in those lost territories preferred leaving their property and escaping into the Anatolian mainland, rather than renouncing their belief and assimilating to the new political regime. Having suffered at the hands of foreign powers, those people have also been especially appreciative of the value of their own soldiers. As for the latter category, dislike of discipline and authority can be mainly attributed to the special social structure and historical circumstances.
文摘Sexual deception involves the mimicry of another species＇ sexual signals in order to exploit behavioural routines linked to those signals. Known sexually deceptive systems use visual, acoustic or olfactory mimicry to exploit insects for preda- tion, cleptoparasitism and pollination. It is predicted that where sexual deception inflicts a cost on the receiver, a coevolutionary arms race could result in the evolution of discriminating receivers and increasingly refined mimicry. We constructed a conceptual model to understand the importance of trade-offs in the coevolution of sexually deceptive mimic and receiver. Four components examined were： the cost of mimicry, the cost to receiver for being fooled, the density of mimics and the relative magnitude of a mimicry-independent component of fitness. The model predicts that the exploitation of non-discriminating receivers by accurate signal mimicry will evolve as an evolutionary stable strategy under a wide range of the parameter space explored. This is due to the difficulty in minimising the costs of being fooled without incurring the cost of falsely rejecting real mating opportunities. In the model, the evolution of deception is impeded when mimicry imposes substantial costs for both sides of the arms race. Olfac- tory signals that are potentially cheap to produce are therefore likely to be more vulnerable to exploitation than expensive visual ornaments
