Sex-specific effects of altered competition on nestling growth and survival: an experimental manipulation of brood size and sex ratio.
Sex-specific effects of altered competition on nestling growth and survival: an experimental manipulation of brood size and sex ratio.
复制标题
改变竞争对雏鸟生长和生存的性别特异性影响：对雏鸟大小和性别比例的实验控制。
DOI：
10.1111/j.1365-2656.2008.01505.x
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
J. Tinbergen
中科院分区：
文献类型：
--
作者：
M. Nicolaus;S. Michler;R. Ubels;M. van der Velde;J. Komdeur;C. Both;J. Tinbergen
1.成虫或雏鸟之间竞争的增加通常会对繁殖产量产生负面影响。然而，人们对竞争对后代性别的不同影响知之甚少。这可能很重要，因为它可能会影响父母的生育决定。2.在性别大小二型物种中，假设父母不差异喂养其雏鸟，关于竞争对雏鸟性能的性别特异性影响，提出了两个主要的矛盾机制：（i）较大的性别需要更多的资源来生长，对饲养条件的恶化更敏感（“成本性别假说”）;（ii）较大的性别具有竞争优势，在内部育雏竞争和表现更好的不利条件下（“竞争优势假说”）。3.在本研究中，我们操纵的性别特异性的兄弟姐妹竞争的水平在一个大山雀人口（山雀）同时改变育雏大小和育雏性别比在两个层面上：巢（雏鸟之间的食物竞争）和林地父母繁殖（成人之间的食物竞争）。我们调查了是否改变了竞争在雏鸟阶段影响雏鸟的生长性状和生存在巢中，以及是否男性，较大的性别和女性之间的影响不同。4.我们发现一个强大的负面和性别特异性的影响，实验育雏大小对所有的雏鸟性状。在扩大育雏，性别大小二型性较小，这可能是由于偏向死亡率对竞争力较低的个人，即女性的低条件。育雏性别比例对雏鸟生长性状无影响。在自然高密度区域，育雏大小对雏鸟性状的负面影响更强，但我们无法通过实验证实这一点。6.我们的研究结果并不支持“昂贵的性别假设”，因为男性在恶劣的条件下并没有遭受更高的死亡率。“竞争优势假说”也没有得到充分的支持，因为女性并没有遭受更多的男性偏见的育雏。7.我们的结论是，男性雏鸟不太可能是更昂贵的提高，但他们有一个规模相关的竞争优势，在大型育雏，导致死亡率较高的平均较轻的女性巢伴侣。
1. An increase of competition among adults or nestlings usually negatively affects breeding output. Yet little is known about the differential effects that competition has on the offspring sexes. This could be important because it may influence parental reproductive decisions. 2. In sexual size dimorphic species, two main contradictory mechanisms are proposed regarding sex-specific effects of competition on nestling performance assuming that parents do not feed their chicks differentially: (i) the larger sex requires more resources to grow and is more sensitive to a deterioration of the rearing conditions ('costly sex hypothesis'); (ii) the larger sex has a competitive advantage in intra-brood competition and performs better under adverse conditions ('competitive advantage hypothesis'). 3. In the present study, we manipulated the level of sex-specific sibling competition in a great tit population (Parus major) by altering simultaneously the brood size and the brood sex ratio on two levels: the nest (competition for food among nestlings) and the woodlot where the parents breed (competition for food among adults). We investigated whether altered competition during the nestling phase affected nestling growth traits and survival in the nest and whether the effects differed between males, the larger sex, and females. 4. We found a strong negative and sex-specific effect of experimental brood size on all the nestling traits. In enlarged broods, sexual size dimorphism was smaller which may have resulted from biased mortality towards the less competitive individuals i.e. females of low condition. No effect of brood sex ratio on nestling growth traits was found. 5. Negative brood size effects on nestling traits were stronger in natural high-density areas but we could not confirm this experimentally. 6. Our results did not support the 'costly sex hypothesis' because males did not suffer from higher mortality under harsh conditions. The 'competitive advantage hypothesis' was also not fully supported because females did not suffer more in male-biased broods. 7. We conclude that male nestlings are not likely to be more expensive to raise, yet they have a size-related competitive advantage in large broods, leading to higher mortality of their on average lighter female nest mates.