PWRC web-site link USGS web-site link

ComDyn4 - Community Dynamics

COMDYN was developed to estimate parameters associated with community dynamics using presence/absence data from 2 locations or time periods. The basic estimator for species richness underlying all estimators is the jackknife estimator proposed by Burnham and Overton (1978, Biometrika 65:625-633; 1979, Ecology 60:927-936). Application of this estimator to species richness estimation is described and justified by Boulinier, Nichols, Sauer, Hines, and Pollock (1998, Ecology 79:1018-1028) The estimators for community-dynamic parameters and their variances are presented by Nichols, Boulinier, Hines, Pollock, and Sauer (" Inference methods for spatial variation in species richness and community composition when not all species are detected, Conservation Biology, in press; Estimating rates of local species extinction, colonization and turnover in animal communities, Ecological Applications, in press).

Terminology and Notation for Input Data

Sample-1 : the first of 2 locations or times over which change is to be estimated
Sample-2 : the second of 2 locations or times over which change is to be estimated
Subset-A: Subset of species which were observed in both samples: f(i) and n(i) data come from Sample 2,
Subset-B: Subset of species which were observed in both samples: f(i) and n(i) data come from Sample 1,

f(i) = number of species observed at exactly i sites/occasions
n(i) = number of species observed at site/occasion i

Sample 1 f(i)1318969
Sample 1 n(i)2636262928
Sample 2 f(i)1991378
Sample 2 n(i)2335223331
Subset A f(i)881278
Subset A n(i)2130182930
Subset B f(i)515959
Subset B n(i)2231212726

Sample 1 f(i)
Sample 1 n(i)
Sample 2 f(i)
Sample 2 n(i)
Subset A f(i)
Subset A n(i)
Subset B f(i)
Subset B n(i)

Enter the number of iterations for the bootstrap variance estimation:
Enter a seed number for the bootstrap variance estimation: (enter 0 for a random seed)