Chambert Thierry, Rotella Jay J, Garrott Robert A
Department of Ecology, Montana State University, Bozeman, MT, 59717, USA.
J Anim Ecol. 2014 Sep;83(5):1158-68. doi: 10.1111/1365-2656.12211. Epub 2014 Mar 17.
Although the quantification of individual heterogeneity in wild populations' vital rates has recently attracted growing interest among ecologists, the investigation of its evolutionary consequences remains limited, mainly because of the difficulties in assessing fitness and heritability from field studies on free-ranging animals. In the presence of individual variability, evaluation of fitness consequences can notably be complicated by the existence of trade-offs among different vital rates. In this study, to further assess the evolutionary significance of previously quantified levels of individual heterogeneity in female Weddell seal (Leptonychotes weddellii Lesson) reproductive rates (Chambert et al. ), we investigated how several life-history characteristics of female offspring were related to their mother's reproductive rate, as well as to other maternal traits (age and experience) and environmental conditions at birth. The probability and age of first reproduction (recruitment) of female offspring was not related to their mother's reproductive rate, suggesting the absence of a maternal trade-off between the number and quality of offspring a female produces. Evidence of a positive, but relatively weak, relationship between the reproductive rates of a mother and her female offspring was found, suggesting some degree of heritability in this trait. Using a simulation approach based on these statistical findings, we showed that substantial differences in the number of grandchildren, produced through female progeny, can be expected among females with different reproductive rates. Despite the presence of substantial stochastic variability, due to environmental fluctuations and other unidentified mechanisms, and in the light of the fact that the metrics obtained do not provide a full measure of real fitness, our results do suggest that the individual reproductive variability found in female Weddell seals could potentially have important fitness consequences.
尽管野生种群生命率的个体异质性量化最近在生态学家中引起了越来越多的关注，但其进化后果的研究仍然有限，主要是因为从对自由放养动物的野外研究中评估适合度和遗传力存在困难。在存在个体变异性的情况下，不同生命率之间权衡的存在会显著使适合度后果的评估变得复杂。在本研究中，为了进一步评估先前量化的雌性威德尔海豹（Leptonychotes weddellii Lesson）繁殖率的个体异质性水平的进化意义（尚贝尔等人），我们研究了雌性后代的几个生活史特征如何与其母亲的繁殖率相关，以及与其他母体特征（年龄和经验）和出生时的环境条件相关。雌性后代首次繁殖（招募）的概率和年龄与其母亲的繁殖率无关，这表明雌性在后代数量和质量之间不存在母体权衡。发现母亲与其雌性后代的繁殖率之间存在正相关但相对较弱的关系，这表明该性状存在一定程度的遗传力。基于这些统计结果，我们采用模拟方法表明，不同繁殖率的雌性通过雌性后代产生的孙辈数量可能存在显著差异。尽管由于环境波动和其他不明机制存在大量随机变异性，并且鉴于所获得的指标不能完全衡量实际适合度，但我们的结果确实表明，在雌性威德尔海豹中发现的个体繁殖变异性可能具有重要的适合度后果。
