Homova not working on 1 out of 2 v.similar datasets

Hello all,

This is my first time analysing NGS (16s) data and I’m following the Miseq SOP. I’m trying to use the HOMOVA command to compare variation between 4 microbial communities. It has worked twice perfectly, for example:

homova(phylip=stability.an.thetayc.0.03.lt.ave.dist, design=14design7.design)

Output:
HOMOVA BValue P-value SSwithin/(Ni-1)_values
1-14-2-8 2.11872 0.004* 0.255805 0.0589287 0.12989 0.155421
1-14 2.08415 0.004* 0.255805 0.0589287
1-2 0.326683 0.198 0.255805 0.12989
1-8 0.218445 0.214 0.255805 0.155421
14-2 0.537003 0.115 0.0589287 0.12989
14-8 0.936382 0.012 0.0589287 0.155421
2-8 0.023833 0.657 0.12989 0.155421

However, when attempting to use HOMOVA on a different set of 4 communities I don’t get the same output - the pairwise comparisons have disappeared:

mothur > homova(phylip=stability.an.thetayc.0.03.lt.ave.dist, design=14design0.design)

Output:
HOMOVA BValue P-value SSwithin/(Ni-1)_values
A-D-B-C 0.315196 0.281 0.203007 0.134267 0.218678 0.121459

These are the two design files for comparison:

14design7.design
group box
R1.1 1
R1.2 1
R1.3 1
R1.4 1
R1.5 1
R1.6 1
R2.1 2
R2.2 2
R2.3 2
R2.4 2
R8.1 8
R8.2 8
R8.3 8
R8.4 8
R8.5 8
R14.1 14
R14.2 14
R14.3 14
R14.4 14
R14.5 14
R14.6 14

14design0.design
group box
A.1 A
A.2 A
A.3 A
A.4 A
A.5 A
A.6 A
B.1 B
B.2 B
B.3 B
C.1 C
C.2 C
C.3 C
D.1 D
D.2 D
D.3 D
D.4 D
D.5 D
D.6 D

But I don’t think the 14design0.design file is at fault because the two design files are nearly identical and i get the pairwise comparisons in the AMOVA ouptut using that design file.

Any ideas or suggestions as to why this is happening and what I could do to fix this? Thanks!

The reason is that the P-value in the second case is 0.281. Since this is not less than 0.05, it does not show the pairwise values. Those do not matter because the original hypothesis test asked whether any of the groups were different from the others - and the answer was no.

Pat