Transcript No Slide Title

Caught in the extinction vortex?
Population dynamics and genetics in a
metapopulation of dunlins
Donald Blomqvist
Dept. Zoology, Univ. Gothenburg, Sweden
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
The aim of our study
Southern Dunlin
Calidris alpina schinzii
The Dunlin
Circumpolar 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 interconnected, local
populations
form a metapopulation
150
12
120
Area (ha)
Number of immigrants
16
8
4
90
60
30
0
0
50
100
150
0
200
16
12
8
4
0
0
10 20 30 40 50 60
Distance nearest site (km)
Distance nearest site (km)
Number of immigrants
Area (ha)
30
25
20
15
10
5
0
Extinct
Not extinct
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?
Data
Long-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
Mean genetic similarity
% Incestuous matings
15
12
9
6
3
0
'93 '95 '97 '99 '01 '03
0.24
0.20
0.16
0.12
0.08
'93 '95 '97 '99 '01 '03
Year
Year
Pedigrees (141 pairs)
DNA fingerprinting
p = 0.038, 40 pairs
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
Hatching success
1.0
0.8
0.6
0.4
0.2
0.0
0.0 0.1 0.2 0.3 0.4 0.5
Genetic similarity
p = 0.024
36 pairs
Mean % heterozygous loci
80
57
p = 0.023
70
60
7
50
40
Hatched
Not hatched
More
homozygous
chicks
die earlier
Homozygous chicks are less likely
to survive to breeding age
% Individuals
100
Heterozygous
Homozygous
23
80
18
60
11
40
20
3
p = 0.032
Returned Not returned
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
...yet the population
continues to decline
40
1.0
Number of pairs
Nest survival probability
Cages improve
nest survival...
0.8
0.6
0.4
35
30
25
20
15
0.2
No
Yes
Nest protection
p = 0.048, 86 nests
'93 '95 '97 '99 '01 '03
Year
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
Financial support
Swedish Research Council
(Formas)
County Administration
Board of Halland, Sweden
Co-workers
L.-Å. Flodin
H. Hirsimäki
O. C. Johansson
M. Larsson
A. Pauliny
U. Unger
J. Wallander