Folie 1

Observability and Multi-species Range Models

Bob O'HaraBiK-FFrankfurt am Main, Germany

Want to Know What affects Species Distributions

Source: mrpink http://www.flickr.com/photos/mjadamo/28640174/

Cottage Industry: Niche Models

Presence Only Models

Dealing With Presence Only Data

Create pseudo-absences

From all of the places a species is not found, randomly select some to act as absences

Problem: False Absences

Sampling effort varies

Pseudo-absence methods deal with this poorly

WE NEED SOMETHING BETTER

Estimating Sampling Effort

Repeated visits: can use absences

Use reports of other species as estimate of effort?

Data

Database of UK butterfly records

Use 8 most common species

10km x 10km squares

Covariates: proportion of habitat

The Species

Green Veined White Pieris napi

Source: oldbilluk /oldbilluk/3504529745/

Red Admiral Vanessa atalanta

Source: Durlston Country Parkdurlston/2891053154/

Large White Pieris brassicae

Source: jpockele /jpockele/196916845/

Meadow Brown Maniola jurtina

Source: Durlston Country Park durlston/2553616249/

Speckled Wood Pararge aegeria

Source: Yersiniayersinia/3465615645/

Small TortoiseshellAglais urticae

Source: Wanja Krah wanjakrah/4552290666/

Peacock Inachis io

Source: Chris@184 chrisbradbury/2745513954/

Small White Pieris rapae

Source: MarcelGermain marcelgermain/1935857010/

Images from www.flickr.com

The
Data

Square root of no. of visits shown

The Model

Process Modeland Sampling Model

http://pixdaus.com/single.php?id=235258&from=email

Process Model

Ii presence of species s at site i

Xij proportion of habitat of type j at location i

Gij Latitude/longitude at location i

SSVS

P(b) = Pr(I=0) N(0, sb2) + Pr(I=1) N(0, c sb2)

Mixture of Normals

c=1000

Spike

Slab

Observation Model

Yi(s) Species s observed in sample j

Pr(Yi(s) = 1 | Ii = 0) = 0

logit(Pr(Yi(s) = 1 | Ii = 1)) = f(s) + yi

Observed|Present = Site + Species

Implementation

MCMC: OpenBUGS

Vague Priors

2 chains, 10k iterations

Large data set takes a few days

The Results

Maps

Black: P=1

Small
White

Results: Observation Effort

Darker= more effort

Habitat Effects

Black=positive, red=negative

Species' Detectabilities

Lat
and
Long
Effects

50% Confidence regions

So?

We Can Do It

Should improve the predictions

Uses the data more efficiently

For the Future

Add climate

Multi-species interactions at process level?

http://services.niagaracollege.ca/unitedway/virtual%20break.htm

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