Table 1 

Summary of estimators used, their formulae and main reference. 

Estimator 
Formula^{§} 
Reference 


Basic Distance (BD) estimators 

Compound of CI, NN & 2NN (BDAV3) 
BDCI = 1/(4 [∑ R_{(1)i}/N]^{2}) 
[1] 
BDNN = 1/(2.778 [∑ H_{(1)i}/N]^{2} 

BD2N = 1/(2.778 [∑ H_{(2)i}/N]^{2} 

BDAV3 = (BDCI + BDNN + BD2N)/3 

KendallMoran (KM) estimators 

CI and NN Search areas pooled (KMP) 
KMP = {[∑ (p_{i }+ n_{i})]  1}/∑ B_{i} 
[5,6] 
CI, NN and 2NN search areas pooled (KM2P) 
KM2P = {[∑ (p_{i }+ n_{i }+ m_{i})]  1}/∑ C_{i} 
[5] 
Ordered Distance (OD) estimators 

Second Closest Individual (OD2C) 
OD2C = (2N  1)/π∑ (R_{(2)i})^{2} 
[7,8] 
Third closest Individual (OD3C) 
OD3C = (3N  1)/π∑ (R_{(3)i})^{2} 

AngleOrder (AO) estimators 

Second closest individual in each quadrant (AO2Q) 
[7,8] 

Third closest individual in each quadrant (AO3Q) 
[7,8] 

Variable Area Transect (VAT) 

Variable Area Transect 
V AT = (3N  1)/(w∑ l_{i}) 
[9] 
Quadrat (QUAD) 

Quadrat 
QUAD = ∑ q_{i}/l_{i}w_{i}N) 
[17] 


CI – closest individual, NN – nearest neighbor, 2NN – second nearest neighbor. R_{(1)i }= the distance from the i^{th }sample point to the CI; R_{(2)i }= the distance from the i^{th }sample point to the second CI; R_{(3)i }= the distance from the i^{th }sample point to the third CI; R_{(3)ij }= the distance from the i^{th }sample point to the third CI for the j^{th }quadrant; H_{(1)i }= the distance from the ith CI to its NN; H_{(2)i }= the distance from the NN at the i^{th }random point; p_{i}, n_{i}, m_{i }= the number of Cis, NNs and 2^{nd }NNs respectively, B_{i }= the total search area at the i^{th }sample point for the CI and NN combined; C_{i}, = the total search area at the i^{th }sample point for the CI, its NN, and the second NN combine; N = the sample size (number of random sample points used to gather distance information); w_{i }= width of quadrat; w = width of transect; l_{i }= length of quadrat. 

White et al. BMC Ecology 2008 8:6 doi:10.1186/1472678586 