CUCKOOS VERSUS REED WARBLERS - ADAPTATIONS AND COUNTERADAPTATIONS
CUCKOOS VERSUS REED WARBLERS - ADAPTATIONS AND COUNTERADAPTATIONS
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DOI：
10.1016/s0003-3472(88)80269-0
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发表时间：
1988-02-01
期刊：
影响因子：
2.5
通讯作者：
BROOKE, MD
中科院分区：
文献类型：
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作者：
DAVIES, NB;BROOKE, MD
在英国剑桥郡的研究地点，在2年内，被杜鹃（Cuculus canorus）寄生的苇莺（Acrocephalus scirpaceus）巢的百分比为22.5%和9.1%。莺拒绝杜鹃卵的19%的寄生巢。寄生的离合器遭受较少的捕食比unparasitized离合器，这表明杜鹃本身是主要的捕食者，掠夺巢太先进的寄生，使主机将重新奠定。杜鹃产假卵，寄生于寄主产卵期的下午，通常移走一个寄主卵，产下一个非常小的卵，产卵速度非常快。用模型卵对巢进行实验性寄生，以研究这一过程的意义。实验表明，寄主辨别选择：（1）杜鹃的卵拟态（匹配较差的模式卵更容易被拒绝）;（2）产蛋期寄生（在宿主产卵前放入巢中的模拟卵都被拒绝）;（3）下午铺设（模仿卵在清晨比在下午更不容易被接受，因为下午宿主更经常不在巢穴中）;（4）小蛋（大蛋，典型的非寄生杜鹃，更容易被拒绝）;（5）快速产卵（巢上的填充杜鹃刺激增加对模型蛋的拒绝）;（6）设定杜鹃移除宿主蛋的限制（如果移除一个或两个以上，可能会发生遗弃）。拟态也可能被选择，因为它减少了第二只杜鹃区分第一只杜鹃的蛋和宿主的蛋的机会。捕食没有选择模仿，巢与非模仿蛋没有遭受更大的捕食比那些模仿蛋。宿主对模型卵的排斥并不取决于：（1）一旦宿主产卵开始，其寄生阶段（尽管如此，杜鹃更可能在宿主产卵期早期产卵，可能是为了增加杜鹃雏鸟孵化的机会）;（2）移除宿主卵（然而，这降低了未孵化卵的发生率，因此杜鹃可能会移除宿主卵，以免超过宿主孵化极限）。拒绝的代价有两种，一种是“弹射”代价（自己的蛋和布谷鸟蛋一样被弹射出来），另一种是“识别”代价（自己的蛋被弹射出来，而不是布谷鸟蛋）。苇莺不歧视不同的小鸡（另一个物种），也不喜欢布谷鸟小鸡或自己的小鸡，当这些被放在两个巢并排。可能的原因，主机歧视不同的鸡蛋，但不像小鸡进行了讨论。
At study sites in Cambridgeshire, England, the percentage of reed warbler, Acrocephalus scirpaceus, nests parasitized by cuckoos, Cuculus canorus, in 2 years was 22.5% and 9.1%. The warblers rejected cuckoo eggs at 19% of parasitized nests. Parasitized clutches suffered less predation than unparasitized clutches, suggesting that the cuckoo itself was the major predator, plundering nests too advanced for parasitism so that the hosts would re-lay. The cuckoos laid a mimetic egg, parasitized nests in the afternoons during the host laying period, usually removed one host egg, laid a remarkably small egg and laid very quickly. Nests were experimentally parasitized with model eggs to study the significance of this procedure. Experiments showed that host discrimination selects for: (1) egg mimicry by cuckoos (poorer matching model eggs were more likely to be rejected); (2) parasitism during the laying period (mimetic eggs put in nests before host laying began were all rejected); (3) afternoon laying (mimetic eggs were less likely to be accepted in the early morning than in the afternoon, when hosts were more often absent from the nest); (4) a small egg (large eggs, typical of non-parasitic cuckoos, were more likely to be rejected); (5) rapid laying (a stuffed cuckoo on the nest stimulated increased rejection of model eggs), and (6) sets a limit to host egg removal by cuckoos (if more than one or two are removed desertion may occur). Mimicry may also be selected for because it reduced the chance that second cuckoos can discriminate the first cuckoo''s egg from the hosts''s clutch. Predation did not select for mimicry; nests with a non-mimetic egg did not suffer greater predation than those with a mimetic egg. Host rejection of model eggs did not depend on: (1) stage of parasitism once host egg laying had begun (nevertheless cuckoos were more likely to lay early in the host laying period probably to increase the chance the cuckoo chick hatched); (2) removal of a host egg (however, this reduced the incidence of unhatched eggs so cuckoos may remove a host egg so as not to exceed the host incubation limit). There were two costs of rejection, an ''ejection'' cost (own eggs ejected as well as the cuckoo egg) and, with mimetic eggs, a ''recognition'' cost (own eggs ejected instead of the cuckoo egg). Reed warblers did not discriminate against unlike chicks (another species) and did not favour either a cuckoo chick or their own chicks when these were placed in two nests side by side. Possible reasons why the hosts discriminate against unlike eggs but not unlike chicks are discussed.