"Subclassing and Composition – A Pythonic Tour of Trade-Offs", Hynek Schlawack
Centre for Genetic Resources The Netherlands
1. Marleen Cobben
Centre for Genetic Resources
The Netherlands
CGN, met goede opmaak
2. Postdoc at CGN
The effects of climate change on wild relatives of crops
important for European breeders
3. Starting with gap analysis
• Using gap analysis and GCM to assess future habitat
areas for CWR
• Here at CIAT for two weeks to learn this methodology
• Important tool to get an estimate of the vulnerability of
species to climate change
• Species with declining or disappearing habitat area are
considered vulnerable
5. Gap analysis
• I am currently however inclined to think that we should
prioritise the collection of species in populations we think
will go extinct soon.
• This is not necessarily the same
• The focus shifts from species to populations
• In the following I will explain why I feel this way
• And I like to hear your thoughts about this
6. Marleen Cobben René Smulders Jana Verboom Rolf Hoekstra Paul Opdam
Adapt, move or perish
The interaction of range shifts and
genetics under climate change
12. Climate change
• Natural populations of species need to respond to
climate change. They may
– track suitable climate, and thus shift their range
– adapt to changed climate
• These responses may occur together and interact
• In my thesis I investigated both responses and their
interaction
13. Research question
How will the level and distribution of neutral genetic
diversity in metapopulations be affected by range shifts
which are induced by current climate change?
14. Climate scenarios
• Overall increased temperature
– Hadley Centre:
• 1 C warming by 2100
• 2 C warming by 2100
• 4 C warming by 2100
• Increased weather variability: more weather extremes
15. Simulation study
• METAPHOR: simulates metapopulation demography
• + shaking windows: simulates temperature increase and
weather variability
• + genetics: each individual has its own genome
100 genes, diploid
WHAT DOES IT LOOK LIKE?
16. North
METAPHOR Habitat patch
individuals of the species
chance to survive
2000 km
chance to breed
chance to disperse
South
20. North
+ shaking windows
climate translates to habitat Habitat becomes suitable
quality
chance to survive Shaking movement
chance to breed of bell shaped window
2000 km
chance to disperse
Optimal Habitat
each year varies randomly
around the optimum
but on average moves Habitat deteriorating
northwards:
1 C : 2 km/year
2 C : 4 km/year
4 C : 8 km/year
South
21. North
+ genetics
neutral genes
diploid inheritance
recombination
2000 km
mutations: 10-4 per generation
(microsatellite mutation rate)
numbers of alleles per locus
effective numbers of alleles per locus
spatial distribution of both
South
22. North
+ genetics
2000 km
number of alleles: 7
effective number of alleles: 5.33
South
23. Simulation result
climate optimum: 400 km
temperature speed: 2 km/year, so 1 C scenario
weather variability: 140 km
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40. Concluding
Under 2 and 4 degrees temperature increase scenarios the
metapopulation goes extinct
All temperature increase scenarios show loss of neutral
genetic diversity as a combination of ‘allele surfing’ at the
leading edge and ‘allele wipe-out’ at the trailing edge
Cobben et al. 2011 Ecography
44. So
Enhancing landscape connectivity may lead to a delayed
loss of genetic diversity in metapopulations under
climate change
But additional measures are likely necessary to ensure
its long-term conservation
Cobben et al. 2012 Landscape Ecology
45. Well....
Surely genetic variation that is selected for will not go
extinct...
And adaptation will improve either the species’ tracking
capabilities or its local survival?
46. Modelling adaptive genetic diversity
• Up till now neutral genes: not affecting individual
performance
• Set of models allowing selection for traits or a
combination of traits
• Under temperature increase and increased weather
variability
47. Research question
What is the outcome of the interaction of local evolution
and range shifts when the central populations in the
species range differ genetically from the marginal
populations?
49. North
Central-marginal model
climate GENERALISTS versus
climate SPECIALISTS
2 traits involved:
- experienced maximum habitat
quality
chance to survive
chance to breed
chance to disperse
- thermal tolerance
South
55. Compare N in time:
metapopulation with specialists and generalists SG, and
2 single genotype metapopulations, G and S
56. So
• Increase of the generalist numbers is not local evolution
towards increased frequency of better-adapted genotype
but an effect of the range shift
• Range shift causes maladaptation of the species:
specialist and generalist genotypes are in the wrong
location
• This affects the metapopulation size
• Temperature increase can ultimately lead to extinction of
the specialist allele and of the metapopulation
Cobben et al. Global Change Biology, online
57. Evolution of dispersal
• Range shifts are known to lead to increased dispersal
capacity at range borders
58. Short wing vs
long wing
Long wing vs
extra-long wing
Thomas et al. 2001 Nature
59. Hmmm....
• I wonder if this pattern could be partly explained by
founder effects as a result of the range shift....
60. Research questions
Will range shifts lead to selection for increased dispersal
probability in the metapopulation?
Could this increase be caused by founder effects?
If so, are there adverse effects of this?
61. Dispersal probability model
Individuals in the model have different
chances of leaving their patch to disperse
6 alleles coding for 11 different levels of
dispersal probability
AA AB BB BC CC CD DD DE EE EF FF
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Initialisation of the model with alleles A-C
Mutations A-F
62. temperature speed: 2 km/year, so 1 °C scenario
mutation rate 10e-6
Dispersal probability
0.0
0.1
0.2
67. So
• The pattern of genotypes is not caused solely by
selection pressure
• And is thus partly the result of the local availability of the
genotypes
• Under climate change, evolution towards increased
dispersal probability is therefore enhanced by the
founder effect
68. But this has a drawback when selection
pressure changes
69. So
• Under stable climate conditions the metapopulation
consisted of only 0.0, 0.1 and 0.2 dispersal probability
individuals
• Under temperature increase we saw selection for the 0.2
dispersal probability genotype
• The increase of this genotype was additionally enhanced
by the founder effect
• But when temperature stabilised the local lack of genetic
variation for dispersal probability caused a slow recovery
of the optimal distribution of genotypes
70. So this may be partly caused by a
founder effect
Short wing vs
long wing
Long wing vs
extra-long wing
Thomas et al. 2001 Nature
71. With short-term positive effect
Short wing vs
long wing
Long wing vs
extra-long wing
Thomas et al. 2001 Nature
72. But possibly a long-term negative effect
Short wing vs
long wing
Long wing vs
extra-long wing
Thomas et al. 2001 Nature
73. Overall conclusions
1. The founder effect is an important determinant of the
allele composition in newly established populations
under range shift across fragmented habitat.
2. The genetic impoverishment resulting from such founder
events requires considerable restoration time in fragmented
habitat and may consequently be a risk to species’ survival.
74. Implications
• We are investigating future suitable habitat areas for
species that are currently shifting their ranges
• And basing our estimate of their vulnerability on the
amount of habitat left
• But we don’t know whether these species will actually be
able to reach these new areas
• And if they do, they may look very different
• I therefore suggest that we further investigate whether to
prioritise the collection of genetic diversity in populations
assessed to go extinct soon
