Zhang He, Rebke Maren, Becker Peter H, Bouwhuis Sandra
Institute of Avian Research 'Vogelwarte Helgoland', An der Vogelwarte 21, D-26386, Wilhelmshaven, Germany.
Avitec Research GbR, Sachsenring 11, D-27711, Osterholz-Scharmbeck, Germany.
J Anim Ecol. 2015 Jan;84(1):199-207. doi: 10.1111/1365-2656.12259. Epub 2014 Jul 22.
Reproductive value is an integrated measure of survival and reproduction fundamental to understanding life-history evolution and population dynamics, but little is known about intraspecific variation in reproductive value and factors explaining such variation, if any. By applying generalized additive mixed models to longitudinal individual-based data of the common tern Sterna hirundo, we estimated age-specific annual survival probability, breeding probability and reproductive performance, based on which we calculated age-specific reproductive values. We investigated effects of sex and recruitment age (RA) on each trait. We found age effects on all traits, with survival and breeding probability declining with age, while reproductive performance first improved with age before levelling off. We only found a very small, marginally significant, sex effect on survival probability, but evidence for decreasing age-specific breeding probability and reproductive performance with RA. As a result, males had slightly lower age-specific reproductive values than females, while birds of both sexes that recruited at the earliest ages of 2 and 3 years (i.e. 54% of the tern population) had somewhat higher fitness prospects than birds recruiting at later ages. While the RA effects on breeding probability and reproductive performance were statistically significant, these effects were not large enough to translate to significant effects on reproductive value. Age-specific reproductive values provided evidence for senescence, which came with fitness costs in a range of 17-21% for the sex-RA groups. Our study suggests that intraspecific variation in reproductive value may exist, but that, in the common tern, the differences are small.
繁殖价值是生存和繁殖的综合度量，对于理解生活史进化和种群动态至关重要，但对于繁殖价值的种内变异以及解释这种变异（如果存在的话）的因素知之甚少。通过将广义相加混合模型应用于普通燕鸥（Sterna hirundo）基于个体的纵向数据，我们估计了特定年龄的年度存活概率、繁殖概率和繁殖表现，并据此计算了特定年龄的繁殖价值。我们研究了性别和招募年龄（RA）对每个性状的影响。我们发现年龄对所有性状都有影响，存活和繁殖概率随年龄下降，而繁殖表现在趋于平稳之前先随年龄提高。我们仅发现性别对存活概率有非常小的、勉强显著的影响，但有证据表明特定年龄的繁殖概率和繁殖表现会随着招募年龄的增加而降低。结果，雄性的特定年龄繁殖价值略低于雌性，而在最早的2岁和3岁时招募的两性鸟类（即燕鸥种群的54%）的适合度前景比晚些时候招募的鸟类略高。虽然招募年龄对繁殖概率和繁殖表现的影响在统计上是显著的，但这些影响还不足以转化为对繁殖价值的显著影响。特定年龄的繁殖价值为衰老提供了证据，对于性别 - 招募年龄组而言，衰老伴随着17% - 21%的适合度成本。我们的研究表明繁殖价值可能存在种内变异，但在普通燕鸥中，差异很小。
