Elucidating The Mechanisms Behind Successful Indicators

of Biodiversity

Joshua Lawler National Research Council / U.S. Environmental Protection Agency

Denis WhiteU.S. Environmental Protection Agency

Lawrence MasterNatureServe, Boston, Massachusetts USA

Overview

1. What surrogates are and why we use them

2. A comparison of surrogate group performance in two regions

3. An investigation of four potential explanations of surrogate group performance

Selecting Areas to Protect Biodiversity

• Maximize the representation of biodiversity

• Provide for viable populations and functioning ecosystems

Surrogates of Biodiversity

• Lack of data requires shortcuts

…successful shortcuts

Surrogates of Biodiversity

• Indicators

• Focal species

• Umbrellas

• Keystones

Testing Surrogates

• Correlations

• Hotspot Overlap

• Complementarity 020406080

100120140160

0 10 20 30 40

Amphibian species richness

Bird

spe

cies

rich

ness

Why do results differ?

• Types of tests are often different

• Different surrogate groups are tested

• Studies are conducted at different scales

• Location

How do surrogates work?

Study regions

Data: sampling grid

~650 km2

Species Occurrence Data

Compiled by The Nature Conservancy and Natural Heritage Programs.

Species Taxon East West

Fish 251 79

Birds 208 267

Butterflies 150 172

Mussels 93 6

Amphibians 78 34

Mammals 76 142

Reptiles 64 29

Site Selection

Stochastic optimization:

simulated annealing

A Comparison of Surrogate Performance

Is there consistency in the performance of surrogate groups across regions ?

East vs. West%

Non

-sur

roga

te g

roup

spe

cies

cov

ered

Surrogate group

EastWest

0102030405060708090

100

Conclusions

• Amphibians, reptiles, and mussels are better surrogates in the east.

• Mammals, birds, and butterflies are better surrogates in the west.

• Fish and rare species are the best surrogates in both regions

Why?

How do surrogates work?Or

What makes a good surrogate?

• They represent biodiversity hotspots

• They are taxonomically diverse

• They are rare

• They (as a group) inhabit diverse environments

Analysis of 100 groups of surrogates

• randomly selected 100 sets of 20 species from a pool of 920 species

• Selected sets of sites to include all species in each set at least one time

• compared performance of each group to group attributes including:

- hotspot overlap- taxonomic diversity- mean range size- environmental diversity

Performance of randomly selected surrogates

0

5

10

15

20

25

30

35

40

45 50 55 60 65 70 75 80

% Coverage

Freq

uenc

y

Hotspots

404550556065707580

3 4 5 6 7 8

% overlap with richness hotspots

% C

over

age

Taxonomic diversity

404550556065707580

4 5 6 7 8404550556065707580

2 7 12 17

% C

over

age

Classes Orders

Families

Genera

404550556065707580

8 13 18404550556065707580

14 16 18 20 22

%

Cove

rage

Range size

Maximum range diameter (km)

404550556065707580

300 400 500 600 700

% C

over

age

Environmental diversity

404550556065707580

0.3 0.4 0.5 0.6 0.7

Land-cover dissimilarity

% C

over

age

Comparison of random surrogates to the best surrogates

• randomly selected 100 sets of 20 species from the pool of 920 species

• optimally selected 100 of the “best” groups of surrogates

• Selected sets of sites to include all species in each set at least one time

• compared the two groups with respect to:- hotspot overlap- taxonomic diversity- mean range size- environmental diversity

Performance of randomly selected and optimally selected surrogates

0

10

20

30

40

50

60

% Coverage

Freq

uenc

y

45 50 55 60 65 70 75 80 85 90

RandomBest

Comparison of randomly selected and optimally selected surrogates

Attribute Random Best

Hotspot overlap (%) 6.0 (0.8) 4.7 (0.7)Taxonomic diversity: classes 6.4 (0.7) 6.3 (0.7) orders 11.0 (1.7) 11.6 (1.5) families 15.0 (1.8) 14.6 (1.9) genera 19.0 (1.1) 19.0 (1.1)Range diameter (km) 539 (68) 313 (59)Environmental dissimilarity 0.46 (0.05) 0.60 (0.03)

The simple answer

Number of sites (total area)

% C

over

age

40

50

60

70

80

90

100

0 2 4 6 8 10 12 14 16 18 20

The simple answer

Range size

Environmental diversity

Number of sites

Performance

Controlling for number of sites:Performance

0

10

20

30

40

50

60

% Coverage

Freq

uenc

y

45 50 55 60 65 70 75 80

RandomBest

Controlling for number of sites:Range Sizes

0

100

200

300

400

500

600

700

Ma x

imu m

rang

e di

a met

er

(km

)

Random

Best

Conclusions

• For relatively simple reasons good surrogate groups contain rare species that together occupy diverse environments.

• Neither taxonomic diversity nor hotspot representation appear to be key attributes of successful surrogates.

• Further research needs to be done to get to the root of surrogate performance

Acknowledgements

Pilar Hernandez, Roly Russell, Anne Guerry, John Van Sickle, National Research Council

(NRC), U.S. Environmental Protection Agency (EPA), Betsy Smith and EPA’s Regional

Vulnerability Assessment Program (ReVA)