1. No category

The term is split roughly into (intellectual) thirds:
What is biodiversity?
species & phylogenies
and how is it patterned?
hollow curves
Where is biodiversity?
measurement, latitudinal gradients
and why is it there?
species-area curves, energy, etc.
(Why) is biodiversity important?
productivity, values of biodiversity
How are those values expressed?
legislation
where are all these species (space)?
Evolutionary
timescales
Evolutionary and
Ecological time scales
Evolutionary and
Ecological time scales
Different patterns at different scales, so include
both ecological and evolutionary time
speciation and extinction
immigration, species interactions, local extinctions
Background reading for next few weeks:
Purvis and Hector (2000) “Getting the measure of Biodiversity”
1
First pattern: why do larger areas have more species?
Rosenzweig, 95
SAC predict species richness,
and can be used to predict current extinction rates...
SAC predict species richness,
and can be used to predict current extinction rates...
“Species-Area Curves”. Issues include:
1.!
Empirical note: Log-Log plot
2. !
Three illuminating curves:
!
!
!
- among subplots of a biogeographic province
- among isolated islands within a province
- among independent biogeographic provinces
Put all three on one graph, and then explore each in turn
slope
1. Empirical note: Raw data is a curve of diminishing returns
(power law with exponent z<1)
S=cAz
intercept
LogS=zLog(A) + Log(c)
high z = 0.15
area
2.2000
species number
low z = 0.1
150.0000
1.9000
high z
Log(c)=1.75
log(#Spp)
117.5000
1.6000
low z
# species
Log(c)=1.5
1.3000
85.0000
high c
1.0000
52.5000
0
low c
75
1.5000
2.2500
3.0000
log(Area)
20.0000
0
0.7500
150
Area
225
300
intercept is the expected richness at Log(A)=0
(and so obviously is scale dependent)
Question: How do B vs B' abundance distributions differ?
1
within province ‘1’
log(#Spp)
Rarefaction
Species observed
All Species-Area relationships are governed by four
forces: immigration, extirpation, speciation and extinction
islands of ‘1’
2
between provinces
‘1’ and ‘2’
B´
A
B
not observed
sample
size
Number of
individuals
log(Area)
Biogeographic province: an area whose species-richness
dynamics are governed principally by speciation and extinction
folks don’t like this
within province curves tend to be relatively shallow
!
islands are steeper than their province
!
!
between provinces the steepest
Island: an area whose species-richness dynamics are governed
most by immigration and extirpation
1
within province 1
log(S)
1's islands
(One taxon's island is another's province)
2
log(A)
between provinces
1 and 2
Three Species-Area Curves
Species-Area relationships
for birds
1. Within provinces!
spatial scale
(Gaston & Blackburn, 2000)
A. Within provinces - nested subsets
nested subset: larger samples are not independent of
smaller samples, so statistical analyses are hard to do.
z=0.11
A. Within Provinces...
Possible hypotheses for intraprovincial curve:
1
log(S)
1. Larger areas sample more individuals
2. Larger areas sample more habitats
2
Given all the bird data from the UK, how could we test
the first, statistical artifact?
bit of total area
log(A)
all of area 1
Why do we have fewer species in smaller subplots?
1. Census a small area - get average # spp and
! record the average number of individuals
2. Draw the same number of individuals randomly from the
entire Province (e.g. all the breeding pairs in the UK).
Repeat 100 times to get a confidence interval.
3. Is it the same as your small area? If it is, this is consistent
with the intraprovincial slope being a pure sampling issue.
--could only do this in the UK!
So, from Eastern Wood (16 ha in Surrey, censused ‘49-’79):
168 breeding pairs per year, on average
--average # spp: 31.8 (+/-2.6)
-take samples of 168 from the 62,500 000 breeding pairs (!)
of 540 spp of birds in Britain.
--average number of spp: 45 (+/-3.4) spp.
...so actually get fewer than we expect based on sampling
(and so the null model would predict a shallower slope than
we see. There is something else to explain)
What is our explanation?
So is the increase due to sampling more habitats?
--weak test for Eastern Wood:
Sample 168 from 51, 000 000 pairs (of 80 spp) of deciduous
wood species (100 times)
-get 31.8 (+/-2.4) - exactly the same as average year at EW.
So sampling more species than expected in larger samples
may be due to sampling more habitats
How often do you see grebes in a forest?
Three Species-Area Curves
-- evidence suggests that # of new habitats is a good, but not
perfect predictor of species richness in subplots.
Problem: area may be better predictor of habitat than habitat!
Biogeographic
'realms'/kingdoms
All Species-Area
relationships are governed by four
forces: immigration, extirpation, speciation and extinction
1. Within provinces: often shallow
auto-correlation (subsamples)
sampling + habitat
2. Among provinces:
1
within provinces
log(S)
1's islands
between provinces
2
bewildering taxonomy (provinces/regions, ecozones, etc.)
log(A)
Holt et al., Science, 2013
Oceanic provinces (~10 per each of four 'realms')
"Longhurst Biogeographic Provinces" (Bedford Oceanographic Institute)
Map of the terrestrial zoogeographic realms and regions of the world. Zoogeographic realms and regions are
the product of analytical clustering of phylogenetic turnover of assemblages of species, including 21,037
species of amphibians, nonpelagic birds, and nonmarine mammals worldwide. Dashed lines delineate the 20
zoogeographic regions identified in this study. Thick lines group these regions into 11 broad-scale realms,
which are named. Color differences depict the amount of phylogenetic turnover among realms.
25
26
http://www.vliz.be/vmdcdata/vlimar/files/MetadataLonghurst.htm
World’s Birds (G&B,01)
widespread
species of tree,
many insect spp
r2 = 0.71
limited range tree species, few insect spp
z=0.66, log(c)=1.59
(very steep slope)
Z=0.89, so like interprovincial: hypotheses?
(Rz,’95)
Flowering plants at two scales
z>1
Note: Steep among-province relationships hold within
“groups” (birds, bats, fern-living insects,trees in wet forest) So not just habitat variation at some gross scale.
within Britain
Rosenzweig ‘95
Interesting - (but ...)
Here, we are in the realm of evolutionary time
--Note: new provinces have DIFFERENT species
(different pools), but the pattern is one of numbers (the pattern
is not cumulative like within province...)
-- Bigger areas may support larger populations,
and larger populations often have larger ranges
How does this effect speciation and extinction?
According to Rosenzweig (1995, but still considered relevant):
Larger areas = larger populations = less extinction
Larger ranges are more likely to be bisected
(allopatric speciation)
Diversity leads to specialization, a more sedentary lifestyle,
and more speciation
Obviously, this is pure conjecture (particularly the last one)
We will return to diversification rate and province size when
we consider the tropics next week...
Three Species-Area Curves
Tropical bird (sub)species richness
Dispersal ability may predict richness:
high low
high low
high low
high low
high low
1. Within provinces:!
!
!
!
!
!
!
!
!
!
often shallow
auto-correlation (subsamples)
sampling more individuals
turnover (beta) due to heterogeneity
2. Among provinces:
!
!
!
!
!
!
!
!
!
not subsamples
steepest of three types of curve
higher speciation;lower extinction rate
-both !f(population size, range size)?
3. Among islands of a province:
33
Claire Salisbury et al., 2012
2. islands off the coast of UK
Woodland "islands" for birds in UK (Gaston&Blackburn, 00)
Eastern Wood, Surrey
r2 = 0.66
r2 = 0.82
z=0.32, log(c)=1.17
z=0.28, log(c)=1.65
For one island
“Island Biogeography Theory” (MacArthur and Wilson, 63; Gotteli, 95)
based on four premises - (NB: pure ecology)
As the number of species resident on an island increases:
1. The immigration rate decreases (fewer new species)
2. The extirpation rate increases (competition)
(both absolute and per species rate)
new
species
arrival
rate
(spp/yr)
As the size of the island increases:
3. The immigration rate increases (bigger target)
4. The extirpation rate decreases (larger populations)
species
extirpation
rate
(spp/yr)
equilibrium
few
Immigration and extirpation rate, Eastern Wood, ‘49-’79
many
# spp on island
Compare with bigger island
big island- more species arrive
species
extirpation
rate
species
arrival
rate
-and fewer are lost
few
cross at 32 spp, where 3 new species arrive
and 3 current species are lost = equilibrium point
# spp on island
many
higher equilibrium
This explains the positive slope, but why is the island
curve steeper than the intraprovincial curve?
A
within province ‘A’
log(S)
Islands are separated from the mainland, which is the
source of immigrants. The greater the separation, the more
isolated an island is, reducing immigration rates.
On the mainland, habitat is continuous, allowing immigration
rates to be higher. Many populations may be also be “sinks” only there by virtue of continuous immigration from “sources”.
This allows smaller areas to have more species.
Island
Mainland
islands in ‘A’
log(Area)
For a subplot the
same size as an island...
and more species in mainland plots makes the
mainland slope shallower
Immigration rates are greater
species
extirpation
rate
(per year)
and fewer are lost
new spp
arrival
rate
(per year)
few
Island
# spp
Mainland
logS
within province A
islands in A
A
Islands are farther away, and
are also missing ‘sink’
species, making the island
slopes steeper
many
log Area
Quiz 3 2014
Which set of islands (red or blue)
is likely farther from the mainland?
1. What is the Allee effect? Does it make managing small populations easier or harder?
Why?
2. Describe two areas of biodiversity science where Ne is important.
A
3. What is an "independent contrast"?
4. Draw and clearly label two Relative Species Abundance Curves on on the same axis
for the same assemblage: one with a small sample size, and one with a large sample
size.
log(S)
B
5. Purvis and Hector talk about "Numbers, Evenness and Difference" as facets of
biodiversity in their Box 1. Give two examples of specific measures of "difference",
preferably one that measures within a sample and one that measures across samples.
log(Area)
E2
E1
Wilson & Simberloff, 69
Arthropods on mangrove islands
red set is likely farther from the mainland
note: it is not clear that the slopes must
be different, though they usually are...
E2 (near)
A
log(S)
B
E1 (far)
Fumigated islands
Simberloff and Wilson, '69
log(Area)
all of
NGuinea
pomerine
ants
closer islands
Ok, can we infer when an
island becomes a biogeographical province?
distant islands
MacArthur & Wilson, 1967
ta da - use phylogenies!
Analysis of an evolutionary species-area
relationship (Losos&Schluter,Nature 408:847,’00)
two different processes?
Cuba
Hispaniola
Jamaica
Puerto Rico
Breakpoint
at 3000km2
(L&S,00-fig3)
Hispaniola
8 spp
ln(spp)
Hispaniola
St.Croix
2spp
Martinique
3spp
log(A)
8 spp
ln(spp)
Martinique
St.Croix
2spp
3spp
log(A)
What processes (immigration, extirpation, speciation, extinction)
are implied by these different trees?
Perhaps in situ speciation on large island, but only immigration
on smaller islands
Non-zero
speciation
rate starts at
3000 km2
Add a time axis, and you can calculate speciation rate
(L&S,00-fig2)
-So, whereas island dynamics (and subsamples of provinces)
are governed mainly by:
immigration,
extirpation,
Province dynamics are governed mainly by:
speciation,
extinction
and for Anolis lizards,
Cuba and Hispaniola and Jamaica are not islands
So, what happens when we create ‘Islands’ on the mainland?
Faunal Collapse
Cadiz Township, Wisconsin
Log # Species
Contiguous Habitat
(intraprovincial SAC)
smaller areas lose more species
Log Area
From MacArthur and Wilson 1967, after Curtis 1956
Extirpations From Parks
Parks lose
mammal species
due to
faunal collapse
Species-Area relationships: which z to use?
Intraprovincial
A
Interprovincial
log(S)
W.D. Newmark
1987 (Nature)
A's islands
log(A)
A'
A
most common z used is 0.25 or 0.3, the island curve
(see, e.g. Woodruff, 2001, Pimm, 2002).
area gets smaller
because -ln(x) is close to 1-x for x near 1
ln
S'
A'
= z ln
S
A
S'/S is prop(sppleft)...
A'
ln(1! prop(spplost)) = ! prop(spplost) = !z ln( )
A
prop(lost) = z * prop(arealost) same substitution for area
Here is an example using z~0.15
Eastern North America: in 1870, forest was at low point,
A’= 0.5A (so proportion lost was 0.5)
So proportion species lost = 0.15 x 0.5 = 0.07, or 7%
There were 30 species endemic to the area, so we expect
2-3 extinctions (for endemics, this area is their "province").
proportion species lost per year ~ z(proportion area lost per year)
PIMM SL, ASKINS RA
FOREST LOSSES PREDICT BIRD EXTINCTIONS IN EASTERN NORTH-AMERICA
P NATL ACAD SCI USA 92: 9343-9347 (1995)
And we lost 4 and are losing one more...
Bachman's warbler
(Vermivora bachmani)
red-cockaded
woodpecker
Given the Passenger Pigeon was also heavily persecuted,
this suggests at least 3 extinction due primarily to habitat loss,
making z > 0.15 not unreasonable in this specific case.
Martha, 1914 (wiki)
(This may just be a lucky example.)
Passenger pigeon
(Ectopistes migratorius)
Ivory-billed woodpecker
(Campephilus principalis)*
(Picoides borealis)
Endangered but doing
better
The problem is, we have witnessed many fewer extinctions due to
habitat loss than SAR predicts
Carolina parakeet
(Conuropsis carolinensis)
68
Old alarmist projections of Extinction based on habitat loss:
He and Hubbell (2011, 2012, 2013) point out something important
"One species per hour to one species a day"
Myers, N. The Sinking Ark: A New Look at the Problem of Disappearing Species
(Pergamon, 1979)
Counting species
when you first see
them is different from
counting species
when you last see
them!
"33–50% of all species between the 1970s and 2000"
Lovejoy, T. E. in The Global 2000 Report to the President: Entering the Twenty-First
Century (study director Barney, G. O.) 328–331
"from half to several million species by 2000"
National Research Council. Research Priorities in Tropical Biology (National Academy
of Sciences, 1980)
"50% of species by 2000"
Ehrlich,P.R.&Ehrlich,A.H.Extinction:The Causes and Consequences oft he
Disappearance of Species (Random House, 1981)
EAR=endemics
area relationship
69
He and Hubbell (2011)
Hanski et al., 2013 make a different point
first time you encounter
a species (SAR z)
island curve
ln(spp)
last time you encounter
species (EAR z)
ln(spp)
But landscapes are not
just getting smaller, but
also fragmented!
So z should be STEEPER!
ln(area)
For imminent extinctions, it is only when the entire range is gone that
the species goes extinct...and this happens much more slowly with area
- so, the z you use to calculate extinction should be LESS than SAR z.
ln(area)
72
And Rosenzweig (2001) goes much further: both intraprovincial
and island curves are based on source-sink dynamics
Ultimate drop should be based on interprovincial curves
(area is lost forever, dynamics are speciation and extinction).
Early stage: local endemics lost
minor
losses
log(S)
Later stage: poor dispersers lost
1
A
major
losses
A's islands
between provinces
log(S)
and here z approaches unity...
This is much worse...
log(A)
A'
A
log(A)
How much land are we losing presently? Lets look at the tropics:
And the tropics are special:
Millennium Ecosystem Assessment (2005) published
0.25% of humid tropical forest conversion per year
Achard et al. (2002) suggest 0.52%/yr.
Pimm (2002) suggests 1%/yr
-most species live there!
This would suggest we sentence up 0.25 to 1% of
tropical species to extinction, every year!
A'
A