Descamps Sébastien, Boutin Stan, McAdam Andrew G, Berteaux Dominique, Gaillard Jean-Michel
Chaire de Recherche du Canada en Conservation des Ecosystèmes Nordiques et Centre d'Etudes Nordiques, Université du Québec à Rimouski, 300 allée des Ursulines, Rimouski, Québec, Canada G5L 3A1.
Proc Biol Sci. 2009 Mar 22;276(1659):1129-35. doi: 10.1098/rspb.2008.1401.
The costs of reproduction are expected to be higher under unfavourable conditions, so that breeding in years of low food supply should have important costs. In addition, the costs of reproduction may be contingent on the age of individuals, and young growing and old senescent individuals should suffer higher costs than the prime-age ones. We tested these predictions by investigating the costs of reproduction as a function of food availability and age in female North American red squirrels using the long-term data on survival and reproduction. We found that the costs of reproduction were independent of food supply, and we did not detect any trade-off between the current and future reproduction. We also did not detect any survival cost of reproduction for the prime-age females, but found evidence for survival costs in yearlings and old (6 years or above) females with successfully breeding individuals having a lower chance of survival compared with unsuccessful or non-breeding ones. These results supported our prediction that the costs of reproduction depended on the age of female red squirrels and were higher in young growing and old senescent individuals. Our study also indicated that, in contrast to large herbivores, heterogeneity in individual quality and viability selection in red squirrels do not affect the study of trade-offs and of the age variation in life-history traits.
在不利条件下，繁殖成本预计会更高，因此在食物供应不足的年份进行繁殖应该会有重大成本。此外，繁殖成本可能取决于个体的年龄，幼年成长中的个体和老年衰老个体应比壮年个体承受更高的成本。我们利用北美雌性红松鼠生存和繁殖的长期数据，通过研究繁殖成本如何随食物可获得性和年龄变化，来检验这些预测。我们发现繁殖成本与食物供应无关，并且我们没有发现当前繁殖和未来繁殖之间存在任何权衡。我们也没有发现壮年雌性存在任何繁殖的生存成本，但发现一岁龄和老年（6岁及以上）雌性存在生存成本的证据，成功繁殖的个体与未成功繁殖或不繁殖的个体相比，存活几率更低。这些结果支持了我们的预测，即繁殖成本取决于雌性红松鼠的年龄，并且在幼年成长中和老年衰老个体中更高。我们的研究还表明，与大型食草动物不同，红松鼠个体质量的异质性和生存能力选择并不影响对权衡以及生活史特征年龄变化的研究。
