Curtis Thomas P, Sloan William T, Scannell Jack W
Department of Civil Engineering, Centre for Molecular Ecology, University of Newcastle upon Tyne, Newcastle upon Tyne NE1 7RU, United Kingdom.
Proc Natl Acad Sci U S A. 2002 Aug 6;99(16):10494-9. doi: 10.1073/pnas.142680199. Epub 2002 Jul 3.
The absolute diversity of prokaryotes is widely held to be unknown and unknowable at any scale in any environment. However, it is not necessary to count every species in a community to estimate the number of different taxa therein. It is sufficient to estimate the area under the species abundance curve for that environment. Log-normal species abundance curves are thought to characterize communities, such as bacteria, which exhibit highly dynamic and random growth. Thus, we are able to show that the diversity of prokaryotic communities may be related to the ratio of two measurable variables: the total number of individuals in the community and the abundance of the most abundant members of that community. We assume that either the least abundant species has an abundance of 1 or Preston's canonical hypothesis is valid. Consequently, we can estimate the bacterial diversity on a small scale (oceans 160 per ml; soil 6,400-38,000 per g; sewage works 70 per ml). We are also able to speculate about diversity at a larger scale, thus the entire bacterial diversity of the sea may be unlikely to exceed 2 x 10(6), while a ton of soil could contain 4 x 10(6) different taxa. These are preliminary estimates that may change as we gain a greater understanding of the nature of prokaryotic species abundance curves. Nevertheless, it is evident that local and global prokaryotic diversity can be understood through species abundance curves and purely experimental approaches to solving this conundrum will be fruitless.
人们普遍认为，原核生物的绝对多样性在任何环境中的任何尺度下都是未知且不可知的。然而，要估算一个群落中不同分类单元的数量，并不需要统计其中的每一个物种。对于该环境，估算物种丰度曲线下的面积就足够了。对数正态物种丰度曲线被认为是群落（如细菌群落）的特征，这类群落呈现出高度动态和随机的生长特性。因此，我们能够表明原核生物群落的多样性可能与两个可测量变量的比率有关：群落中的个体总数以及该群落中最丰富成员的丰度。我们假设最不丰富的物种丰度为1，或者普雷斯顿的标准假说是有效的。由此，我们可以在小尺度上估算细菌多样性（海洋中每毫升160种；土壤中每克6400 - 38000种；污水处理厂中每毫升70种）。我们还能够推测更大尺度上的多样性，因此海洋中细菌的整体多样性可能不会超过2×10⁶种，而一吨土壤可能包含4×10⁶种不同的分类单元。这些都是初步估计，随着我们对原核生物物种丰度曲线本质的进一步了解，可能会有所变化。然而，很明显，通过物种丰度曲线可以理解局部和全球的原核生物多样性，而单纯通过实验方法来解决这个难题将是徒劳的。
