This package provides functions to fit twenty models to species-area relationship (SAR) data (see Triantis et al. 2012), plot the model fits, and to construct a multimodel SAR curve using information criterion weights. A number of additional SAR functions are provided, e.g. to fit the log-log power model, the general dynamic model of island biogeography (GDM), and Coleman's Random Placement model.
Functions are provided to fit 20 individual SAR models. Nineteen are
fitted using non-linear regression, whilst a single model (the linear
model) is fitted using linear regression. Each model has its own function
(e.g. sar_power). A set of multiple model fits can be
combined into a fit collection (fit_collection). Plotting
functions (plot.sars) are provided that enable individual
model fits to be plotted on their own, or the fits of multiple models to be
overlayed on the same plot. Model fits are validated using a number of
checks, e.g. the normality and homogeneity of the model residuals can be
assessed.
A multimodel SAR curve can be constructed using the sar_multi
function. This fits up to twenty SAR models and constructs the multimodel
curve (with confidence intervals) using information criterion weights (see
summary.sars to calculate a table of models ranked by
information criterion weight). The plot.multi functions
enables the multimodel SAR curve to be plotted with or without the fits of
the individual models.
Other SAR related functions include: (i) lin_pow, which fits
the log-log power model and enables comparison of the model parameters with
those calculated using the non-linear power model, (ii) gdm,
which fits the general dynamic model of island biogeography (Whittaker et
al. 2008) using several different functions, and (iii)
coleman, which fits Coleman's (1981) random placement model
to a species-site abundance matrix.
Coleman, B. D. (1981). On random placement and species-area relations. Mathematical Biosciences, 54, 191-215.
Guilhaumon, F., Mouillot, D., & Gimenez, O. (2010). mmSAR: an R-package for multimodel species<U+2013>area relationship inference. Ecography, 33, 420-424.
Matthews, T.J., Guilhaumon, F., Triantis, K.A, Borregaard, M.K., & Whittaker, R.J. (2015b) On the form of species<U+2013>area relationships in habitat islands and true islands. Global Ecology & Biogeography. DOI: 10.1111/geb.12269.
Triantis, K.A., Guilhaumon, F. & Whittaker, R.J. (2012) The island species<U+2013>area relationship: biology and statistics. Journal of Biogeography, 39, 215-231.
Whittaker, R.J., Triantis, K.A. & Ladle, R.J. (2008) A general dynamic theory of oceanic island biogeography. Journal of Biogeography, 35, 977-994.
# NOT RUN {
data(galap, package = "sars")
#fit the power model
fit <- sar_power(galap)
summary(fit)
plot(fit)
#Construct a multimodel SAR curve
fit_multi <- sar_multi(galap)
summary(fit_multi)
plot(fit_multi)
# }
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