Behavioural Ecology Research Group, Department of Evolutionary Zoology, University of Debrecen, Debrecen, Hungary.
PLoS One. 2010 Dec 3;5(12):e14215. doi: 10.1371/journal.pone.0014215.
Many animals display colorful signals in their integument which convey information about the quality of their bearer. Theoretically, these ornaments incur differential production and/or maintenance costs that enforce their honesty. However, the proximate mechanisms of production costs are poorly understood and contentious in cases of non-carotenoid-based plumage ornaments like the melanin-based badge and depigmented white wing-bar in house sparrows Passer domesticus. Costly life-history events are adaptively separated in time, thus, when reproduction is extended, the time available for molt is curtailed and, in turn, molt rate is accelerated.
METHODOLOGY/PRINCIPAL FINDINGS: We experimentally accelerated the molt rate by shortening the photoperiod in order to test whether this environmental constraint is mirrored in the expression of plumage ornaments. Sparrows which had undergone an accelerated molt developed smaller badges and less bright wing-bars compared to conspecifics that molted at a natural rate being held at natural-like photoperiod. There was no difference in the brightness of the badge or the size of the wing-bar.
CONCLUSIONS/SIGNIFICANCE: These results indicate that the time available for molt and thus the rate at which molt occurs may constrain the expression of melanin-based and depigmented plumage advertisements. This mechanism may lead to the evolution of honest signaling if the onset of molt is condition-dependent through the timing of and/or trade-off between breeding and molt.
许多动物在其表皮显示出丰富多彩的信号，这些信号传递着关于其携带者质量的信息。从理论上讲，这些装饰物会产生不同的生产成本和/或维护成本，从而增强其真实性。然而，在非类胡萝卜素基羽毛装饰物的情况下，如黑色素基徽章和家麻雀 Passer domesticus 的去色素白色翼带，生产成本的近因机制理解不足且存在争议。代价高昂的生活史事件在时间上是自适应分离的，因此，当繁殖延长时，用于换羽的时间就会缩短，换羽速度也会加快。
方法/主要发现：我们通过缩短光照周期来加速换羽速度，以测试这种环境约束是否反映在羽毛装饰物的表达上。与在自然光照周期下以自然速度换羽的同种麻雀相比，经历加速换羽的麻雀的徽章更小，翼带也不那么明亮。徽章的亮度和翼带的大小没有差异。
结论/意义：这些结果表明，换羽可用的时间（即换羽速度）可能会限制黑色素基和去色素羽毛广告的表达。如果换羽的开始取决于繁殖和换羽之间的时间和/或权衡，那么这种机制可能会导致诚实信号的进化。
