Lang S L C, Iverson S J, Bowen W D
Department of Biology, Dalhousie University, Halifax, Nova Scotia B3H4J1, Canada.
Ecology. 2009 Sep;90(9):2513-23. doi: 10.1890/08-1386.1.
In mammals, the most significant maternal effect on offspring growth during lactation is the ability of females to efficiently transfer milk energy to their neonates. However, despite the importance of the transfer of milk energy to both maternal and offspring fitness, nothing is known about the extent to which variation among females may be attributed to differences in individual quality or environmental variation in natural populations. We measured repeatability over multiple lactation periods in components of lactation performance in free-ranging, multiparous gray seal (Halichoerus grypus) females to examine to what extent variation among females in pup weaning mass may be attributed to inherent differences in their physiological capacity to deliver milk energy. Levels of repeatability were high for milk composition (r = 0.38-0.50), daily milk output (r = 0.46), and the duration of lactation (r = 0.57), demonstrating that there are consistent differences among females in these characters across lactations and that the overall capacity of gray seal females to deliver milk energy to their pups is characteristic of individuals. The repeatability in pup weaning mass (r = 0.48) was consistent with the values for the components of total milk energy output and suggests that, over a large proportion of their reproductive life, individual gray seal females will consistently wean pups with greater or lesser probabilities of survival. Our results suggest that inherent differences among females in their physiological capacity to deliver milk energy may be an important component of variation in individual quality and, thus, lifetime reproductive success in mammals. High levels of repeatability also suggest that components of milk energy transfer may have a significant heritable genetic basis.
在哺乳动物中，哺乳期母体对后代生长最重要的影响是雌性将乳汁能量有效传递给幼崽的能力。然而，尽管乳汁能量传递对母体和后代的健康都很重要，但对于自然种群中雌性之间的差异在多大程度上可归因于个体质量差异或环境变化，我们却一无所知。我们测量了自由放养的多胎灰海豹（Halichoerus grypus）雌性在多个哺乳期的泌乳性能组成部分的重复性，以研究雌性之间幼崽断奶体重的差异在多大程度上可归因于它们输送乳汁能量的生理能力的内在差异。乳汁成分（r = 0.38 - 0.50）、每日乳汁产量（r = 0.46）和哺乳期时长（r = 0.57）的重复性水平较高，这表明在这些特征上，雌性在不同哺乳期之间存在一致的差异，并且灰海豹雌性向幼崽输送乳汁能量的总体能力具有个体特征。幼崽断奶体重的重复性（r = 0.48）与总乳汁能量输出组成部分的值一致，这表明在其大部分繁殖生命中，个体灰海豹雌性断奶的幼崽生存概率会持续存在较大或较小的差异。我们的结果表明，雌性在输送乳汁能量的生理能力上的内在差异可能是个体质量差异的一个重要组成部分，因此也是哺乳动物一生繁殖成功率的重要组成部分。高重复性水平还表明，乳汁能量传递的组成部分可能具有显著的遗传基础。
