TABLE 3.

Alpha diversity estimates

Sample	Age (yr)	Alpha diversitya
		Shannon index			PD
		Avg	SE	P value	Avg	SE	P value
Untreated	19,000	7.53	0.10	1.3 × 10−5b	37.82	0.69	1.7 × 10−6b
	27,000	4.84	0.11	0.1150c	16.25	0.43	1.7 × 10−2c
	33,000	5.33	0.12	3.8 × 10−3d	21.63	0.58	1.3 × 10−2d
DNA depleted	19,000	7.70	0.09	3.4 × 10−3b	38.51	0.71	1.2 × 10−3b
	27,000	4.98	0.08	0.2293c	16.50	0.34	0.0771c
	33,000	5.28	0.13	0.0605d	21.92	0.46	0.0771d
Endospore enriched	19,000	7.50	0.08	1.6 × 10−3b	32.83	0.53	1.6 × 10−3b
	27,000	4.00	0.18	0.1039c	12.55	0.79	0.1039c
	33,000	5.34	0.30	0.0990d	18.15	0.94	0.0990d

^aAlpha diversity estimates based on 16S rRNA gene sequences for the untreated samples, PMA-treated samples, and endospore-enriched samples across the three age groups were measured using QIIME. Overall diversity was lowest in the intermediate-age samples. Within treatment types, differences between age groups were tested using a Kruskal-Wallis test and Dunn’s post hoc test. The values are averages of five replicates, and significant P values are shown in boldface.

^bVersus 27,000 years.

^cVersus 33,000 years.

^dVersus 19,000 years.