Appendix C. Lack of evidence for gap dependence.
|
Genus |
Species |
Abundance (stems/ha) |
Size difference between nearest neighbors (mm dbh) – observed |
N† |
Size difference between nearest neighbors (mm dbh) – simulated |
Estimated gap dependence (P value) |
|
Bursera |
instabilis |
42.594 |
7.167 (6.27) |
58 |
8.653 (0.88) |
0.141 |
|
arborea |
19.956 |
5.716 (4.944) |
50 |
6.767 (0.80) |
0.187 |
|
|
excelsa |
8.638 |
5.914 (3.52) |
25 |
5.643 (0.81) |
0.658 |
|
|
Caesalpina |
eriostachys |
36.339 |
9.97 (8.49) |
60 |
10.406 (1.13) |
0.700 |
|
sclerocarpa |
5.064 |
6.38 (5.67) |
21 |
8.063 (1.36) |
0.217 |
|
|
coriaria |
2.383 |
9.136 (7.77) |
31 |
9.089 (1.29) |
0.971 |
|
|
Cordia |
alliodora |
39.019 |
11.73 (8.07) |
52 |
11.01 (1.14) |
0.405 |
|
eleaegnoides |
2.085 |
20.04 (21.47) |
14 |
42.56 (10.48) |
0.197 |
|
|
Jatropha |
chamelensis |
6.255 |
2.20 (4.23) |
14 |
2.44 (1.04) |
0.815 |
|
standleyi |
5.064 |
6.35 (3.86) |
17 |
5.36 (1.11) |
0.372 |
Notes: Gap dependence was estimated by comparing observed mean dbh difference between conspecific nearest neighbor pairs with mean nearest neighbor dbh difference of 10,000 simulated communities of the same size (N). Simulated communities were constructed by random selection without replacement from the pool of diameters present in the real community. The P value of this comparison indicates whether a hypothesis of gap dependence may be accepted (P < 0.05); P values are sometimes also used to signify degree of gap dependence (Lusk and Smith 1998). None of the species examined showed evidence of significant dependence on gaps, nor is there evidence of correlation between species abundance and degree of gap dependence. NB: Although not used in analyses of recruitment fluctuations due to lack of growth rate data, Caesalpinia coriaria was included here because it had been selected for the study of Kelly et al. (2001) using the same criteria of ecological similarity as that applied to the other nine species.
† N = number of pairs.
Kelly, C. K., H. Banyard Smith, Y. M. Buckley, R. Carter, M. Franco, W. Johnson, T. Jones, B. May, R. Perez Ishiwara, A. Perez-Jimenez, A. Solis Magallanes, H. Steers, and C. Waterman. 2001. Investigations in commonness and rarity: a comparative analysis of co-occuring, congeneric Mexican trees. Ecology Letters 4:618–627.
Lusk, C. H., and B. Smith. 1998. Life history differences and tree species coexistence in an old-growth New Zealand rain forest. Ecology 79:795–806.