Donald Blomqvist

Dept. Zoology, Univ. Gothenburg, Sweden

Caught in the extinction vortex?

Population dynamics and genetics in a metapopulation of dunlins

Small and isolated populations risk extinction for several reasons

• Changes in demography and environment

• Genetic threats- Inbreeding- Genetic drift- Mutation accumulation

• Together form an ”extinction vortex”

Inbreeding

• More immediate threat than other genetic factors

• Related parents produce more homozygous offspring: expression of recessive, detrimental alleles

• Reduction in individual fitness: inbreeding depression

• Well documented in plants and animals

Influence of inbreeding and loss of genetic diversity on extinction risk

• Theoretically expected

• Supported by computer simulations, lab experiments, and studies of plants and butterflies in the wild

• Still few studies of natural populations

Southern Dunlin Calidris alpina schinzii

The aim of our study

The DunlinCircumpolar breeding

distribution

Winters in temperate or tropical areas

Mean lifespan 5-7 years, max ~ 20 years

Socially monogamous

Several subspecies

The Southern Dunlin

Breeds in SE Greenland and NW Europe

In the Baltic Sea region, confined to wet pastures and meadows

Habitat loss - large population decline

Endangered

Study population

Several inter-connected, local populations form a meta-population

Area (ha)

0 50 100 150 200

0

4

8

12

16

Nu

mb

er o

f im

mig

ran

ts

Distance nearest site (km)

0 10 20 30 40 50 60

0

4

8

12

16

Nu

mb

er o

f im

mig

ran

ts

Extinct Not extinct

Dis

tan

ce n

eare

st s

ite

(km

)

0

5

10

15

20

25

30

Are

a (h

a)

0

30

60

90

120

150

More extinctions than re-colonizations of local populations

The entire metapopulation is threatened by

extinction

Questions

1. Population decline associated with more matings between related individuals?

2. Fitness consequences?

3. Is habitat management sufficient for preserving the Southern Dunlin?

DataLong-term study:

Population, pedigree and individual fitness data

Two types of molecular markers:

• DNA fingerprinting: Genetic similarity of mates

• Microsatellite genotyping (7 loci): Individual genetic diversity

Questions

1. Population decline associated with more matings between related individuals?

2. Fitness consequences?

3. Is habitat management sufficient for preserving the Southern Dunlin?

Increased frequency of matings between related individuals

Pedigrees (141 pairs) DNA fingerprintingp = 0.038, 40 pairs

Year

'93 '95 '97 '99 '01 '03

% In

cest

uo

us

mat

ing

s

0

3

6

9

12

15

Year

'93 '95 '97 '99 '01 '03

Mea

n g

enet

ic s

imila

rity

0.08

0.12

0.16

0.20

0.24

Questions

1. Population decline associated with more matings between related individuals?

2. Fitness consequences?

3. Is habitat management sufficient for preserving the Southern Dunlin?

Related parents suffer increased hatching failure

p = 0.02436 pairs

Genetic similarity

0.0 0.1 0.2 0.3 0.4 0.5

Hat

chin

g s

ucc

ess

0.0

0.2

0.4

0.6

0.8

1.0

Morehomozygous

chicksdie earlier

p = 0.023

Hatched Not hatched

Mea

n %

het

ero

zyg

ou

s lo

ci

40

50

60

70

80

57

7

Homozygous chicks are less likely to survive to breeding age

Returned Not returned

% I

nd

ivid

ual

s

20

40

60

80

100HeterozygousHomozygous

23

3

18

11

p = 0.032

Questions

1. Population decline associated with more matings between related individuals?

2. Fitness consequences?

3. Is habitat management sufficient for preserving the Southern Dunlin?

Protective nest cages 2001-2004

Cages improve nest survival...

...yet the population continues to decline

p = 0.048, 86 nests

Nest protection

No Yes

Nes

t su

rviv

al p

rob

abil

ity

0.2

0.4

0.6

0.8

1.0

Year

'93 '95 '97 '99 '01 '03

Nu

mb

er o

f p

airs

15

20

25

30

35

40

Conclusions

The population decline of the Southern Dunlin has serious genetic consequences

Habitat management seems insufficient for preserving the Southern Dunlin

Ignoring genetics will underestimate extinction risks and may lead to inappropriate conservation measures

Co-workers

L.-Å. Flodin

H. Hirsimäki

O. C. Johansson

M. Larsson

A. Pauliny

U. Unger

J. Wallander

Financial support

Swedish Research Council (Formas)

County Administration Board of Halland, Sweden

THANKS!