What is Biodiversity? - MiamiCh20)Part...What is Biodiversity? Biodiversity in Plants Gaston and Blackburn 2000 Latitude & Diversity in Birds in the New World High Species Richness

What is Biodiversity?

Biodiversity in Plants

Gaston and Blackburn 2000

Latitude & Diversity in Birds in the New World

High Species Richness

High Endemism

High Threat of Extinction

More species in Tropics •! Noted by Darwin & by Wallace

Why?

Quick Primer to Diversity Measures

Species Richness: number of species in a given area/plot

-! How certain are scientists that they have catalogued all species in plot?

-! Is this a fair/adequate measure of biodiversity?

Classic example by Preston (1948): Relationship between number of species and number of individuals sampled

Species Abundance: Rothamsted Moths (collected during a single night in 1935)

•! 6814 individuals collected •! 197 species total •! 6 species comprise ~ ! all individuals •! 1 species comprise ~ " all individuals •! 37 species represented by single individual Figure from Dobson 1998

Rare species are common

Common species are rare

Rare Species Common Species

Number of Individuals Represented in Sample

Num

ber

of S

peci

es

Preston s Log-normal Distribution"

Figure from Dobson 1998

Rothamsted, UK Lepidoptera light trap catch

Number of individuals represented in sample

Num

ber

of s

peci

es

Data from Preston 1948, figure from Molles 2005

Number of individuals

Number of individuals

Num

ber

of s

peci

es

Num

ber

of s

peci

es

Sample with 300,000 moths reveals more of the distribution

Sample of 87,000 moths from Canadian prairie reveals only part of the distribution

Species abundance curves

No.

of

spec

ies

No. of individuals few many

abundant

not abundant

•!Number of species that are rare are common •!Number of species that are common are rare

Patterns of abundance

–! A few abundant species dominate

–! Many non-abundant species

Species Number Weighted by Sample Size

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Explicitly consider sample because number of species discovered increases with the number of individuals sampled (non-linear, could be logarithmic).

Forest Diversity: Which forest is most diverse? "

Forest A " "Forest B " "Forest C"Hemlock " "Hemlock " "Hemlock"Beech " "Beech " "Beech"Red Maple" "Red Maple" "Red Maple"Yellow Birch"White Ash"Black Cherry"Basswood"

Species Diversity: Components"

Species Richness = number of species present "

Evenness = degree of similarity in relative abundance of different species"

Which forest is most diverse?" Forest A Forest B Forest C

Hemlock 144 50 90 Beech 1 50 40 Red Maple 1 50 20 Yellow Birch 1 White Ash 1 Black Cherry 1 Basswood 1

•!Forest A: high richness and low evenness

•!Forest B: low richness and high evenness

•!Forest C: low richness and moderate evenness

HOW CAN WE COMBINE THE TWO?

Si as a diversity measure

Simpson s index of evenness

pi = the proportion of the individuals in the community belonging to species i

Si = 1/ (!pi 2)

Shannon-Wiener Diversity Index#

•!Incorporates both species richness and evenness"•!Gives more weight to common species "

H = value of Shannon-Wiener index "s = number of species in community"pi = proportion of the ith species"logepi = the natural log of pi"

s H' = -" (pi)(logepi) i=1

Number Proportion (pi) logepi (pi)(logepi) Hemlock 144 0.9600 -0.041 -0.039 Beech 1 0.0067 -5.006 -0.033 Red Maple 1 0.0067 -5.006 -0.033 Yellow Birch 1 0.0067 -5.006 -0.033 White Ash 1 0.0067 -5.006 -0.033 Black Cherry 1 0.0067 -5.006 -0.033 Basswood 1 0.0067 -5.006 -0.033

TOTAL 150 1

Calculating H' "

H' = - " (pi)(logepi) i=1

s 0.237

-0.237

Number Proportion (pi) logepi (pi)(logepi) Hemlock 50 0.3333 -1.099 -0.366 Beech 50 0.3333 -1.099 -0.366 Red Maple 50 0.3333 -1.099 -0.366 Yellow Birch 0 White Ash 0 Black Cherry 0 Basswood 0

TOTAL 150 1

Calculating H' "

H' = - " (pi)(logepi) i=1

s 1.10

-1.099

Which forest is most diverse?" Forest A Forest B Forest C

Hemlock 144 50 90 Beech 1 50 40 Red Maple 1 50 20 Yellow Birch 1 White Ash 1 Black Cherry 1 Basswood 1

H' 0.24 1.10 0.93 vs.

Species # 7 3 3

Scales of Species Diversity"

Alpha Diversity = local diversity within a uniform habitat type (i.e., within-habitat diversity)"

Beta Diversity = among-habitat diversity"•! Measured as rate of species turnover between

habitats "•! Often expressed as Gamma/Alpha diversity"

Gamma Diversity = number of species observed in all habitats within a region (i.e., regional diversity)"

Robert Whittaker"

Scales of Diversity"

## = 6

Alpha

(species per mountain)

A B

C D

E F B

C D

E F

A B

C D

E F

G

Region 1

A B

C D E

F G

D G

H I

J ## = 4 $$ = 10 %% = 2.5

Region 2

A B

C ## = 3 $$ = 9 %% = 3.0 D E

F G H

I

Region 3

(species per region)

Gamma

$$ = 7

(gamma/ alpha)

Beta

%% = 1.2

Beta diversity is “turnover” in diversity across habitats

Beta Diversity"

Beta diversity between two communities

Jaccard similarity = C/(C + U1 + U2)

Sorenson similarity = C/((S1 + S2/2))

C = number of species in common U = number of unique species S = number of species

Range 0 (dissimilar) to 1 (identical)

Beta Diversity"

Greater distance = Smaller J (more diff) Beta diversity (change in J) increases from N to S

Why?

Which Mountain Do I Conserve?

Species Island 1 Island 2 Island 3

A 16 5 0

B 1 7 0

C 1 3 0

D 1 8 0

E 1 0 0

F 0 0 10

G 0 0 10

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•! More species in Tropics. Why? -! Non-equilibrium, Time hypothesis -! Equilibrium, balance between loss and gain of species (but why do they differ?)

General Patterns with Species Diversity

•! Species-area relationship •! Latitude, environmental heterogeneity

and habitat Productivity

Species-area relationship

•! More species are found in larger areas than in smaller ones

•! S = c Az

•! log S = log c + z log A

Larger area, more species

WHY?

1.! Sampling 2.! Habitat variation 3.! Unique evol

lineages across continents

Islands Also Follow Species-area Relationship Birds of Solomon Islands Diamond and Mayr 1976

Number of species increases with island area. Why?

•! Previous three factors + probability of extinction/colonization.

How? 1) Large islands are better targets (more colonists) 2) Large islands have bigger populations (less likely to

go extinct).

Equilibrium balance between extinction and colonization (we’ll come back to this later on….)

Islands Also Follow Species-area Relationship Anoles of the Carribean Losos and Schluter 2000

Why?

General Patterns with Species Diversity

•! Species-area relationship •! Latitude, environmental heterogeneity

and habitat productivity can explain large scale patterns of diversity

Latitudinal Gradient

N to S gradient: Temperature/prod

E to W gradient: Environ het

Isolated: Dispersal

Within region (latitude): Habitat Complexity

Within region (latitude): Habitat Complexity

Within region (latitude): Productivity

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Back to the Tropics vs. Temperate

•! More ecological niches •! Intermediate Disturbance •! Herbivore and Pathogen •! Random ecological drift