donald blomqvist dept. zoology, univ. gothenburg, sweden caught in the extinction vortex? population...
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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!