WHY DO PARASITIC CUCKOOS HAVE SMALL BRAINS? INSIGHTS FROM EVOLUTIONARY SEQUENCE ANALYSES
WHY DO PARASITIC CUCKOOS HAVE SMALL BRAINS? INSIGHTS FROM EVOLUTIONARY SEQUENCE ANALYSES
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DOI：
10.1111/j.1558-5646.2008.00490.x
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发表时间：
2008-12-01
期刊：
影响因子：
3.3
通讯作者：
Krueger, Oliver
中科院分区：
文献类型：
--
作者：
Boerner, Martina;Krueger, Oliver
大脑的大小面临着许多相反的选择压力。然而，事实证明，估计它们的相对影响并重建大脑的进化史是困难的。在这里，我们证实了幼体寄生杜鹃的大脑相对于它们的体重比非寄生杜鹃的大脑更小的说法。使用系统发育控制的相关性和进化路径分析，对两种解释大脑尺寸缩小的假设进行了检验。在一种新的方法中，路径模型被结合起来，以建立与大脑大小变化相关的最有可能的特征变化的进化序列。在幼虫寄生之前，大脑的大小发生了变化，随后转向生产力较低的栖息地，迁徙增加。这一序列表明，大脑的大小并不是因为与鸡肉供应相关的认知技能的丧失而缩小的，它也不支持能量需求的增加或能量可获得性的减少是为了缩小大脑大小的假设。相反，序列表明，由于较小的大脑尺寸和寄生繁殖策略导致的能量需求的减少，可能使寄生杜鹃能够在新的生态位上定居。
Brain size is under many opposing selection pressures. Estimating their relative influence and reconstructing the brain's evolutionary history have, however, proved difficult. Here, we confirm the suggestion that the brain of brood parasitic cuckoos is smaller in relation to their body weight than that of nonparasitic cuckoo species. Two hypotheses explaining reductions in brain size are tested, using phylogenetically controlled correlations and evolutionary pathway analyses. In a novel approach, the pathway models are combined to build the most likely evolutionary sequence of trait changes correlating with changes in brain size. Brain size changed before brood parasitism, followed by a shift toward less-productive habitats and an increase in migration. This sequence shows that brain size was not reduced as a consequence of a loss of cognitive skills related to chick provisioning, and it offers no support for the hypothesis that an increase in energetic demands or a reduction in energy availability selected for a reduction of brain size. Instead, the sequence suggests that the reduction in energetic demands due to the smaller brain size and parasitic breeding strategy may have enabled parasitic cuckoos to colonize new niches.