Rickard Ian J, Russell Andrew F, Lummaa Virpi
Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK.
Proc Biol Sci. 2007 Dec 7;274(1628):2981-8. doi: 10.1098/rspb.2007.1051.
Life-history theory states that reproductive events confer costs upon mothers. Many studies have shown that reproduction causes a decline in maternal condition, survival or success in subsequent reproductive events. However, little attention has been given to the prospect of reproductive costs being passed onto subsequent offspring, despite the fact that parental fitness is a function of the reproductive success of progeny. Here we use pedigree data from a pre-industrial human population to compare offspring life-history traits and lifetime reproductive success (LRS) according to the cost incurred by each individual's mother in the previous reproductive event. Because producing a son versus a daughter has been associated with greater maternal reproductive cost, we hypothesize that individuals born to mothers who previously produced sons will display compromised survival and/or LRS, when compared with those produced following daughters. Controlling for confounding factors such as socio-economic status and ecological conditions, we show that those offspring born after elder brothers have similar survival but lower LRS compared with those born after elder sisters. Our results demonstrate a maternal cost of reproduction manifested in reduced LRS of subsequent offspring. To our knowledge, this is the first time such a long-term intergenerational cost has been shown in a mammal species.
生活史理论指出，生殖事件会给母亲带来代价。许多研究表明，生殖会导致母亲的身体状况、存活率或后续生殖事件中的成功率下降。然而，尽管亲代适合度是子代生殖成功的函数，但生殖成本传递给后续子代的可能性却很少受到关注。在此，我们利用一个工业化前人类群体的谱系数据，根据每个个体的母亲在前一次生殖事件中所付出的代价，比较子代的生活史特征和终生生殖成功率（LRS）。由于生育儿子与更高的母亲生殖成本相关，我们假设，与母亲生育女儿后出生的个体相比，母亲生育儿子后出生的个体的存活率和/或LRS会受到影响。在控制了社会经济地位和生态条件等混杂因素后，我们发现，与姐姐出生后出生的个体相比，哥哥出生后出生的个体存活率相似，但LRS较低。我们的研究结果表明，生殖的母体成本表现为后续子代LRS的降低。据我们所知，这是首次在哺乳动物物种中发现这种长期的代际成本。
