Ecological Archives E088-035-A4

Gregory S. Gilbert, Don R. Reynolds, and Ariadna Bethancourt. 2007. The patchiness of epifoliar fungi in tropical forests: host range, host abundance, and environment. Ecology 88:575–581.

Appendix D. Logistic regression results for the effect of phylogenetic distance (My), joint relative abundance (JRA), or the interaction (MyxJRA) on the probability that two plant species shared epifoliar fungal symbionts, from radial transects at San Lorenzo, Panama and Cape Tribulation, Australia.

Akaike Information Criterion (AIC), Likelihood Ratio (LR), P values of Wald test chi-square estimates for each factor, and percent concordance were used to select the best model for each site. At neither site did phylogenetic distance between plant species pairs contribute significantly to the model. Intercept was always significant (P ≤ 0.004 for all).

       
P values
 
Site
Model
AIC
LR
LR
My
JRA
MyxJRA
Conc.%
SanLorenzo
1
787.4 18.7 0.0003 0.5426 0.0067 0.0532
61.4
SanLorenzo
2
789.3 14.8 0.0006 0.6816 0.0001  
60.8
SanLorenzo
3
802 0.1 0.8379 0.8374    
23.3
SanLorenzo
4
787.4 14.67 0.0001   0.0001  
60.4
SanLorenzo
5
762.7 39.4 0.0001   0.0001†  
63.3
CapeTrib
1
796 27.2 0.0001 0.5328 0.1944 0.9277
63.6
CapeTrib
2
794 27.2 0.0001 0.4079 0.0001  
63.7
CapeTrib
3
818.3 0.9 0.3407 0.3293    
34.8
CapeTrib
4
792.7 26.6 0.0001   0.0001  
62.7
CapeTrib
5
754.7 64.5 0.0001   0.0001†  
71.4

†Model uses log10(joint relative abundance).

At both sites, model 5 was the best, taking the form p(sharing) = expy / (1 + expy) where:
y = 2.0995 + 1.2722 log10JRA (for San Lorenzo)
y = 1.7059 + 1.1563 log10JRA (for Cape Tribulation).
To compare the logistic model predictions to the rates of fungal sharing observed at each site (Fig. 1), we grouped all pairwise joint relative abundances into log-series bins with lower bounds at 0.5x. In each bin, we calculated the proportion of plant pairs that shared fungal taxa.

   
San Lorenzo, Panama
Cape Tribulation, Australia
x
Lower bound
No. shared pairs
No. total pairs
Proportion shared
No. shared pairs
No. total pairs
Proportion shared
19
1.91E-06
0
0
 
0
55
2.85E-06
18
3.82E-06
0
0
 
0
110
5.71E-06
17
7.63E-06
0
0
 
1
133
3.42E-05
16
1.53E-05
6
351
0.0171
10
255
0.0001
15
3.05E-05
0
0
 
9
311
0.0005
14
6.10E-05
11
216
0.0509
9
271
0.0014
13
1.22E-04
42
683
0.0615
28
254
0.0048
12
2.44E-04
17
206
0.0825
14
199
0.0127
11
4.88E-04
20
130
0.1538
13
121
0.0308
10
9.77E-04
8
50
0.1600
13
76
0.0455
9
1.95E-03
4
13
0.3077
6
33
0.0634
8
3.91E-03
0
3
0.0000
4
10
0.0395
7
7.81E-03
0
1
0.0000
0
2
0.0174


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