a) Mean family size against genome size (N
) for genomes of 92 Bacteria (■) and 79 Archaea (◦), both clustered at E
= 1e-20 and f
= 0.7. Analysis of variance showed a significant effect of N
on (F(1, 167) = 421.54, p ≪ 0.001) and a significant interaction between N
and taxa group (F(1, 167) = 28.27, p ≪ 0.001), indicating that the slopes for Bacteria and Archaea were significantly different. Least-squared linear regressions are thus shown separately for Bacteria (dashed line, ) and Archaea (solid line, ). (b) Total number of families (F
) against N
for Bacteria and Archaea, clustered as above. Lines are the regressions from (a), defined by the relation .