Figure 6

Theoretical implications for prokaryotic ecology and prokaryotic genetic diversity of hypotheses proposed here. The irregular shapes filled with different hatching represent different groups of related species; their extended shapes symbolize each group’s genetic diversity. The regions of overlap are subsets of each group genetically specialized to form symbiotic relationships with species in other groups. The circles connected to certain overlaps by dashed lines represent obligatorily symbiotic species, one from each group, that have lost the ability to fulfill complimentary life functions, and thus can reproduce (and be cultured) only as pairs.