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Hierarchical Models for Species Distributions

Bob O'Hara

BiK-F

Frankfurt am Main, Germany

Stuff I'd like to talk about

Dispersal

Dynamics

Processes

Sampling & Observation

http://www.flickr.com/photos/slowloris/

Presence Only Models

Pseudo-absences

MaxEnt

Dave Wharton: Both approximations to point processes

Problem: False Absences

Some things are just not seen

We need to measure effort

Different ways of estimating effort lead to different sampling models

Estimating Sampling Effort

Repeated visits: can use absences

Use reports of other species as estimate of effort?

Data

Database of UK butterfly records

Year 2000

10km x 10km squares

Covariates: proportion of habitat, latitude & longitude

The Model

Process Modeland

Sampling Model

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

Process Model

logit Pr I i s=1=s∑ j s X ij∑ l sG il

Ii – presence of species s at site i

Xij – proportion of habitat of type j at

location i

Gij – Latitude/longitude at location i

Observation Models

Binomial

Poisson

Incidence

Compare several:

None

Binomial Observation Model

Photo:USFWS

r ~ Bin(N, p)

Poisson Observation Model

Photo:USFWS

r ~ Po(Nλ)

Bernoulli Observation Model

Photo:USFWS

At least 1 razorbill

I ~ Bin(1, 1-e-Nλ)

No Observation Model

Adonis Blue

(possibly)http://www.flickr.com/photos/markkilner/3867177467/

Predicted Ranges

Comparing Predictions

Gatekeeper

http://www.flickr.com/photos/duncanh1/3859133643/

Predicted Ranges

(presences slightly offset)

Comparing Predictions

So?

We should include sampling models in our SDMs

Might have to be imaginative about measuring effort

There are several models we could use

For the Future

Better process model

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

Check which model is actually best