CADDIS Volume 4: Data Analysis

## Predicting Environmental Conditions from Biological Observations (PECBO) Appendix

- Introduction

- Using Existing Taxon-Environment

Relationships - Estimating Taxon-Environment

Relationships - Computing Inferences

- R Scripts

##### Topics in Estimating Taxon-Environment Relationships

### Central Tendencies

Taxon-environment relationships can be expressed in terms of *central tendencies* that describe the average environmental conditions under which a taxon is likely to occur. Using this method, the single-value descriptor of the taxon-environment relationship, *u _{wa}*, for taxon

*j*is estimated by computing the mean of the environmental variable of interest at the sites in which the taxon is observed:

where *N* is the total number of sites and *x _{i}* is the value of the environmental variable of interest at site

*i*. For presence/absence data,

*Y*is equal to 1 when taxon

_{ij}*j*is present at site

*i*and 0 when taxon

*j*is absent. For abundance data,

*Y*is the abundance of taxon

_{ij}*j*at site

*i*.

Statistical scripts for computing central tendancies are available under the R Scripts tab of this section.

#### Biological inference

Once central tendencies are computed for each taxon, one can use them to infer conditions at a new site based only on biological observations, by computing a weighted average inference.

**Estimating Taxon-Environment Relationships:** Overview Previous Next