Table 2

Initial similarity† and quartile distance†† in species richness and composition

Initial similarity
 R2
 Quartile distance/km
Similarity in richness





The Americas¤•
 1.00
 0.18*
 1329
Amazon
 0.96
 0.72*
 563
Andes
 0.85
 0.05*
 1700
Caribbean•
 (0.81)
 ns
 (53.295)
C. America•
 0.90
 0.16
 814
Similarity in composition





The Americas¤•
 0.84
 0.47*
 342
Amazon•
 0.91
 0.72*
 751
Andes•
 0.81
 0.18*
 581
Caribbean•
 0.87
 0.73*
 523
C. America•
 0.79
 0.44*
 644

† Initial similarity = the similarity at a distance of 150 km. †† Quartile distance = 0.75 * initial similarity.

¤ Analyses were done for grid-pairs with a geographic distance of ≤ 4.000 km.

• Geographical distance was ln-transformed.

* p < 0.01.

Bjorholm et al. BMC Ecology 2008 8:11   doi:10.1186/1472-6785-8-11