[Biomod-commits] using Migration

[Viorel Popescu]

Hi Wilfried,

I am using centroids of 10x10 km quadrats (approx. 2600 quadrats total) as
the input presence/absence data. I have 22 species and used pseudo-absences
to model current and future distributions for 2 time horizons and 3 climate
change scenarios. Coordinates are in meters, not degrees.

I tried setting MaxMigr to 0, and also 1, 100, 1000, and both 'limited
dispersal' and 'unlimited dispersal' outputs are identical.

Leaving that aside, I don't understand how Biomod.RangeSize predicts pixel
loses and gains with '0 dispersal' and 'unlimited dispersal'. The
Compt.By.Species summary seems to make sense, but which of the 2 scenarios
(0 dispersal or unlimited dispersal) does Diff.By.Pixel data represent? It
almost looks like it shows the unlimited dispersal scenario, but I am
mostly interested in the 'no dispersal' projections of loss and gain. I am
working with reptiles and amphibians, and the 'no dispersal' scenario would
be more realistic. Something in between 0 and unlimited dispersal would be
ideal, and this is where I thought the Migration function comes in handy

Thank you

Cheers,
Viorel



On Fri, Sep 7, 2012 at 1:14 AM, Wilfried Thuiller <
wilfried.thuiller at ujf-grenoble.fr> wrote:

> Hi Viorel,
>
> It has been a long time I did not have a look at this function.
> What is the resolution of your data?
> Just for a first try, what does it happen if you set MaxMig at 0.
>
> Best
> Wilfried
>
>
>
> Le 6 sept. 2012 à 20:04, Viorel Popescu a écrit :
>
> Hi everyone,
>
> I have a few questions about using Migration and how/if it feeds into the
> Biomod.RangeSize function. I produced current and future distributions
> using Ensemble.Forecasting, but now I would like to add more realism using
> the Migration() function and the dispersal parameter MaxMigr. I understand
> that the MaxMigr units have to be in decimal degrees, but no matter if
> MaxMigr = 1000 or MaxMigr = 0.16667, the resulting objects
> (Future20a1b.Migration in my case) are completely identical in terms of
> probability values.
>
> *Migration(CurrentPred = Total_consensus_Current[,,2], FutureProj =
> Total_consensus_Future20a1b[,,2],*
> *X=LatLong[,1], Y=LatLong[,2], MaxMigr=100,
> Pred.Save="Future20a1b.Migration")*
>
> Moreover, when trying to plot the Current, Limited Dispersal and Unlimited
> Dispersal distributions, the latter 2 look identical (again, regardless of
> the value given to MaxMigr)
>
> *par(mfrow=c(1,3))*
> *level.plot(Resp.Var[,'Sp21'], XY=LatLong, show.scale=FALSE,
> title="current distribution", cex=0.8)*
> *level.plot(Future20a1b.Migration[,21], XY=LatLong, show.scale=F,
> title="limited migration", cex=0.8)*
> *level.plot(Total_consensus_Future20a1b_Bin[,21,2], XY=LatLong,
> show.scale=FALSE, title="unlimited migration", cex=0.8)*
>
> Am I doing something wrong with Migration? Also, does the information from
> Migration feed into the RangeSize function? If so, it is not clear to me
> how...
>
> Thanks in advance for any advice
>
> Cheers,
> Viorel
>
>
>
> --
> Viorel D. Popescu, PhD
> David H. Smith Conservation Research Fellow
> University of California - Santa Cruz &
> Simon Fraser University, Biological Sciences
>
>  _______________________________________________
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>
>
> --------------------------
> Dr. Wilfried Thuiller
> Laboratoire d'Ecologie Alpine, UMR CNRS 5553
> Université Joseph Fourier
> BP53, 38041 Grenoble cedex 9, France
> tel: +33 (0)4 76 51 44 97
> fax: +33 (0)4 76 51 42 79
>
> Email: wilfried.thuiller at ujf-grenoble.fr
> Personal website: http://www.will.chez-alice.fr
> Team website: http://www-leca.ujf-grenoble.fr/equipes/emabio.htm
>
> ERC Starting Grant TEEMBIO project:
> http://www.will.chez-alice.fr/Research.html
> FP6 European EcoChange project: http://www.ecochange-project.eu
>
>
>
>
>
>
>
>


-- 
Viorel D. Popescu, PhD
David H. Smith Conservation Research Fellow
University of California - Santa Cruz &
Simon Fraser University, Biological Sciences
8888 University Drive
Burnaby, BC V5A 1S6, Canada
(604) 340 4228
www.umit.maine.edu/~Dan_Popescu/
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