Readings
Species-fragmented area relationship
- Reading for QAECO reading group
- relationship between increasing number of species and increasing
area of habitat
- (so I suppose inverse is true, e.g. climate change reduce area
of habitat, reduce number of species?)
- predict number of extinctions due to loss of habitat
- the issue is fragmentation
- habitat loss generally results in a fragmented (sub) habitat
- SAR assumes contiguous regions (think a circle getting smaller)
- fragmentation is when holes appear (think a doughnut)
- (meta) population capacity is essentially the carrying capacity of
the habitat
- fragmentation causes this to decline
- e.g. due to disconnect between fragments
- SFAR (species-fragmented area relationship) fits better than SAR in
simulations
- Figure 1
- the authors suggest the SAR does not fit the number of species
well, but it looks like it does to me? The lines are pretty
close to the points?
- I think perhaps the figure legend is not described well — the
lines are not SARs but just general fitted lines?
- Species traits
- when including the fragmentation part, the authors suggest a
large amount of variation in the ratio of extinction and
colonisation
- this has an effect on their $b$ parameter
- how are the models fit? stupid pnas, need to check in
supplementary material
- Case study uses only 14 points
- they suggest that species number is reduced due to fragmentation
- a better visualisation would be to use points proportional to
$\lambda$ in Figure 4A
- They suggest hat SFAR is better than SAR, due to a difference in
AICc of 2.44 (!)
- furthermore, the least-squares value of the area coefficient is
negative, meaning that conditional on $\lambda$, the number of
species $S$ is increasing as area $A$ decreases
- what!?
- this same thing happens in eqn 3, where if $z < 0$, if
$A_{\text{new}} < A$, \$S~new~/S >1 \$!
- they do discuss what they term hidden parameters: those used for
estimating $\lambda$
- perhaps these should be estimated in a hierarchical model?