The absolute diversity of prokaryotes

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 3 106, while a ton of soil could contain 4 3 106 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