Table 1.

Comparison of ZPS statistics for two genes: fumC, expected to be under strong purifying selection against structural variation as a housekeeping gene, and fimH, evolving under strong positive selection through SNPs as shown for genes encoding surface adhesins of pathogenic bacteria. The sample includes identical datasets of 75 strains for the two genes [9]. The p-values for the diversity measures are based on differential zonal haplotype diversity [9], while the other significance values are derived using 2 × 2 χ ² statistic. P and E denote Primary and External zones respectively

	zone	fumC	fimH	p-values
no. of strains	P	69	27	< 0.0001
	E	6	48
no. of haplotypes	P	20	14	< 0.0001
	E	3	29
zone-wise structural hot-spot frequency (no. of hot-spots/total no. of mutations)	P	0.00(0/1)	0.00(0/3)	1.00
	E	0.00 (0/3)	0.53 (19/36)	0.039
Simpson's index (λ)	P	0.11 ± 0.01	0.12 ± 0.03	0.002
	E	0.39 ± 0.10	0.07 ± 0.01
α index	P	9.45 ± 1.80	11.71 ± 3.88	0.005
	E	2.39 ± 1.66	31.00 ± 8.25