Fenchel Tom
Laboratory of Ecology, Zoological Institute, University of Åarhus, Åarhus.
Oecologia. 1974 Dec;14(4):317-326. doi: 10.1007/BF00384576.
The relationship between previously published values of "the intrinsic rate of natural increase" (r ) and body weight is studied. When organisms covering a wide range of body weights are compared, a correlation is found which can be described by the equation r =aW where r is the intrinsic rate of natural increase per day and W is the average body weight in grams; a is a constant which takes three different values for unicellular organisms and heterotherm and homoiotherm animals respectively. The constant n has a value of about-0.275 for all three groups. This result is compared to the previously found relationship between the metabolic rate per unit weight and body size. It is shown that r can be inter-preted as the productivity of an exponentially growing population and thus must correlate with metabolic rate. The values of the constants a and n, however, show that for each of the three groups, unicellular organisms, heterotherms and homoiotherms the ratio of energy used for maintenance to that used for production increases with increasing body size and that the evolution from protozoa to metazoa and the evolution from heterotherm to homoiotherm animals in both cases resulted in not only an increased metabolic rate, as shown previously, but also in a decreased population growth efficiency. It is shown that the increase in reproductive potential of homoiotherms relative to that of heterotherms is due to a shorter prereproductive period in the former group.Previous estimates of r for different species and comparisons between these values in relation to their ecology are discussed in context with the found "r -body weight" relationship. Attempts to show that such comparisons will be more meaningful when body size is included in the considerations are made. It is suggested that the found relationship may represent the maximum values r can take rather than average values for all species, since it is likely that the species used for laboratory population-studies are biased in favor of species with high reproductive potentials.
研究了先前发表的“自然增长率”（r ）值与体重之间的关系。当比较涵盖广泛体重范围的生物体时，发现了一种相关性，可用方程r = aW 来描述，其中r 是每日自然增长率，W 是以克为单位的平均体重；a 是一个常数，对于单细胞生物、变温动物和恒温动物分别取三个不同的值。常数n 对于所有三组的值约为 -0.275。将此结果与先前发现的单位体重代谢率与体型之间的关系进行了比较。结果表明，r 可被解释为指数增长种群的生产力，因此必然与代谢率相关。然而，常数a 和n 的值表明，对于单细胞生物、变温动物和恒温动物这三组中的每一组，用于维持的能量与用于生产的能量之比都随着体型的增加而增加，并且从原生动物到后生动物的进化以及从变温动物到恒温动物的进化在这两种情况下不仅如先前所示导致代谢率增加，而且还导致种群增长效率降低。结果表明，恒温动物相对于变温动物生殖潜力的增加是由于前一组的繁殖前期较短。结合所发现的“r -体重”关系，讨论了先前对不同物种r 的估计以及这些值之间与其生态学相关的比较。尝试表明当在考虑中纳入体型时，这种比较将更有意义。有人认为，所发现的关系可能代表r 所能取的最大值而非所有物种的平均值，因为用于实验室种群研究的物种可能偏向于具有高繁殖潜力的物种。
