OA: Overlap Analysis

In modEvA: Model Evaluation and Analysis

Overlap Analysis

Description

This function analyses the range of values of the given environmental variables at the sites where a species has been recorded present.

Usage

OA(data, sp.cols, var.cols)

Arguments

data	a data frame with your species' occurrence data and the predictor variables.
sp.cols	index number of the column containing the occurrence data of the species to be modelled. Currently only one species can be analysed at a time.
var.cols	index numbers of the columns containing the predictor variables to be used.

Details

Overlap Analysis is one of the simplest forms of modelling species' distributions. It assesses the ranges of values of the given environmental variables at the sites where a species has been recorded present, and predicts where that species should be able to occur based on those presence data (e.g. Brito et al. 1999, Arntzen & Teixeira 2006).

OA can also be useful when extrapolating models outside their original scope (geographical area, time period or spatial resolution), as it can identify which localities are within the model's domain - i.e., within the analysed ranges of values of the variables, outside which the model may not be reliable (e.g. Barbosa et al. 2009). In this case, the response is not a species' presence, but rather the sites that have been included in the model. See also the MESS function for a comparison between modelled and extrapolation environments.

Input data for the OA function are a vector or column with ones and zeros (presences vs. absences of a species if we want to model its occurrence, or modelled vs. non-modelled sites if we want to know which non-modelled sites are within the modelled range), and a matrix or data frame with the corresponding values of the environmental variables to consider (one variable in each column, values in rows).

Value

A binary vector whith 1 where the values of all predictors lie within the ranges observed for the presence records, and 0 otherwise.

Author(s)

A. Marcia Barbosa

References

Arntzen J.W, Teixeira J. (2006) History and new developments in the mapping and modelling of the distribution of the golden-striped salamander, Chioglossa lusitanica. Zeitschrift fur Feldherpetologie, Supplement: 1-14.

Barbosa, A.M., Real, R. & Vargas, J.M. (2009) Transferability of environmental favourability models in geographic space: the case of the Iberian desman (Galemys pyrenaicus) in Portugal and Spain. Ecological Modelling 220: 747-754.

Brito J.C., Crespo E.G., Paulo O.S. (1999) Modelling wildlife distributions: Logistic Multiple Regression vs Overlap Analysis. Ecography 22: 251-260.

See Also

MESS

Examples

## Not run: 
# load package 'fuzzySim' and its sample data:
require(fuzzySim)
data(rotif.env)

names(rotif.env)

OA(rotif.env, sp.cols = 18, var.cols = 5:17)

## End(Not run)

modEvA documentation built on Oct. 30, 2024, 1:06 a.m.