Arnott Stephen A, Chiba Susumu, Conover David O
Marine Sciences Research Center, Stony Brook University, Stony Brook, NY 11794-5000, USA.
Evolution. 2006 Jun;60(6):1269-78.
There is strong evidence that genetic capacity for growth evolves toward an optimum rather than an absolute maximum. This implies that fast growth has a cost and that trade-offs occur between growth and other life-history traits, but the fundamental mechanisms are poorly understood. Previous work on the Atlantic silverside fish Menidia menidia has demonstrated a trade-off between growth and swimming performance. We hypothesize that the trade-off derives from the competing metabolic demands associated with growth and swimming activity. We tested this by measuring standard metabolic rate (M(STD)), maximum sustainable metabolic rate (M(ACT)) and metabolic scope of laboratory-reared silversides originating from two geographically distinct populations with well-documented differences in genetic capacity for growth. The fast-growth genotype had a significantly greater M(STD) than the slow-growth genotype, but a similar MACT when swum to near exhaustion. The scope for activity of the fast-growth genotype was lower than that of the slow-growth genotype. Furthermore, the fast-growth genotype eats larger meals, thereby incurring a greater postprandial oxygen demand. We conclude that a metabolic trade-off occurs between growth and other metabolic demands and that this trade-off provides a general mechanism underlying the evolution of growth rate.
有充分证据表明，生长的遗传能力是朝着最优状态而非绝对最大值进化的。这意味着快速生长是有代价的，并且在生长与其他生活史特征之间存在权衡，但其中的基本机制仍知之甚少。先前对大西洋银汉鱼梅氏银汉鱼的研究表明，生长与游泳能力之间存在权衡。我们推测这种权衡源于与生长和游泳活动相关的相互竞争的代谢需求。我们通过测量标准代谢率（M(STD)）、最大可持续代谢率（M(ACT)）以及代谢范围，对来自两个地理上不同种群的实验室饲养银汉鱼进行了测试，这两个种群在生长的遗传能力方面有充分记录的差异。快速生长基因型的标准代谢率（M(STD)）显著高于缓慢生长基因型，但在游至接近疲劳时，最大可持续代谢率（M(ACT)）相似。快速生长基因型的活动范围低于缓慢生长基因型。此外，快速生长基因型进食量更大，从而产生更高的餐后需氧量。我们得出结论，在生长与其他代谢需求之间存在代谢权衡，并且这种权衡为生长速率的进化提供了一种普遍机制。
