Centre for Genetic Resources The Netherlands

Marleen Cobben Centre for Genetic Resources The NetherlandsCGN, met goede opmaak

Postdoc at CGNThe effects of climate change on wild relatives of cropsimportant for European breeders

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

Jarvis et al. AGEE 2008

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

Marleen Cobben René Smulders Jana Verboom Rolf Hoekstra Paul Opdam Adapt, move or perish The interaction of range shifts and genetics under climate change

Collaboration within Wageningen-URPlant BreedingAlterraLand Use PlanningGenetics

MetapopulationsIn fragmented landscapes species are often confined to metapopulations

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

Research questionHow will the level and distribution of neutral geneticdiversity in metapopulations be affected by range shiftswhich are induced by current climate change?

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

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?

NorthMETAPHOR Habitat patchindividuals of the specieschance to survive 2000 kmchance to breedchance to disperse South

NorthMETAPHORindividuals of the specieschance to survive 2000 kmchance to breedchance to disperse South

North+ shaking windowsclimate translates to habitat Habitat becomes suitablequality chance to survive Shaking movement chance to breed of bell shaped window 2000 km chance to disperse Optimal Habitateach year varies randomlyaround the optimumbut on average moves Habitat deterioratingnorthwards: 1 C : 2 km/year 2 C : 4 km/year 4 C : 8 km/year South

North + geneticsneutral genesdiploid inheritancerecombination 2000 kmmutations: 10-4 per generation (microsatellite mutation rate)numbers of alleles per locuseffective numbers of alleles per locusspatial distribution of both South

North + genetics 2000 kmnumber of alleles: 7effective number of alleles: 5.33 South

Simulation result climate optimum: 400 kmtemperature speed: 2 km/year, so 1 C scenario weather variability: 140 km

ConcludingUnder 2 and 4 degrees temperature increase scenarios the metapopulation goes extinctAll temperature increase scenarios show loss of neutralgenetic diversity as a combination of ‘allele surfing’ at theleading edge and ‘allele wipe-out’ at the trailing edge Cobben et al. 2011 Ecography

Maybe it’s the landscape? 2.5% 5% 10%

2.5% landscape area

10% landscape area

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

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?

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

Research questionWhat 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?

Northneutral model 2000 km South

NorthCentral-marginal modelclimate GENERALISTS versusclimate SPECIALISTS2 traits involved:- experienced maximum habitatquality chance to survive chance to breed chance to disperse- thermal tolerance South

NorthCentral-marginal modelclimate GENERALISTS versusclimate SPECIALISTSonly 2 alleles coding forgeneralist and specialist types,heterozygotes are intermediates South

temperature speed: 2 km/year, so 1 °C scenariomutation rate 10e-6

Compare N in time:metapopulation with specialists and generalists SG, and2 single genotype metapopulations, G and S

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

Evolution of dispersal• Range shifts are known to lead to increased dispersal capacity at range borders

Short wing vs long wingLong wing vsextra-long wing Thomas et al. 2001 Nature

Hmmm....• I wonder if this pattern could be partly explained by founder effects as a result of the range shift....

Research questionsWill 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?

Dispersal probability modelIndividuals in the model have differentchances of leaving their patch to disperse6 alleles coding for 11 different levels ofdispersal probabilityAA AB BB BC CC CD DD DE EE EF FF0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0Initialisation of the model with alleles A-CMutations A-F

temperature speed: 2 km/year, so 1 °C scenariomutation rate 10e-6 Dispersal probability 0.0 0.1 0.2

Dispersal probability 0.0 0.1 0.2

This is beneficial for the metapopulation1 metapopulation 3 metapopulationswith all genotypes with single genotypes

However, availability of genetic variation changes the pattern

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

But this has a drawback when selection pressure changes

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

So this may be partly caused by a founder effect Short wing vs long wingLong wing vsextra-long wing Thomas et al. 2001 Nature

With short-term positive effect Short wing vs long wingLong wing vsextra-long wing Thomas et al. 2001 Nature

But possibly a long-term negative effect Short wing vs long wingLong wing vsextra-long wing Thomas et al. 2001 Nature

Overall conclusions1. 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 founderevents requires considerable restoration time in fragmentedhabitat and may consequently be a risk to species’ survival.

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

Thank you

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Centre for Genetic Resources The Netherlands

by CIAT on May 25, 2012

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