[R-sig-ME] Mixed modelling and Species Area Relationship (SAR)

[Ben Bolker]

On 15-11-26 09:09 AM, Gitu wa Mbui wrote:
> How does one account for the species area relationship in a mixed model of
> predicting species richness?
> 
> Sampling was carried out using different methods - photoquadrats, transects
> etc ( five different methods).
> 
> The area of the sampled plots differed and there were hundreds of plots. I
> am constructing a glmm for predicting the species richness, overall, and
> have configured the Method of sampling as a random intercept in the model.
> I am wondering how I should construct the model such the influence of SAR
> is taken into account - considering that SAR can not be a random factor.
> 
> ~Gitu

  This is probably a little bit too vague for most of the people on the
list (who are not ecologists).

   Supposing that you're using a log link for the response (which would
make sense if you plan to treat species richness as Poisson or negative
binomial), try incorporating log(Area) as a covariate.  Then (ignoring
all the other stuff in your model for the moment)

  log(mu) = b0 + b1*log(area)

or

  mu = exp(b0)*exp(b1*log(area)) = C*area^b1

 which looks like a pretty respectable model for the species-area
relationship.

  Ben Bolker