iinvestigation of the genetic basis of adaptation
TRANSCRIPT
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Investigating the genetic basis of adaptation in American pikas
Philippe Henry & Michael RusselloEcological and Conservation Genomics Lab
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• Introduction and background
• Methods and analyzes used
• Preliminary results and anticipated significance
Outline
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• Genetic variation = evolutionary potential of populations or species
• There are two principal types of genetic variation:- Neutral (reflects demographic patterns)- Adaptive (reflects variation under natural
selection)
Introduction
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• Neutral genetic variation: - population genetic structure - demographic events, (bottlenecks and
population expansions)
Valuable information to help prioritize populations for conservation efforts
X. Does not generally inform on long term evolutionary potential of populations
Introduction
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• Adaptive genetic variation can be assessed in wildlife populations
• This information will help
- shed light on the evolutionary potential of populations
- assist management decisions, especially with regard to adaptation to environmental changes
Introduction
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The American pika as a model?
• Species sensitive to high ambient temperatures
• Contemporary climate warming may be partly responsible for the extirpation
• Good candidate to study the genetic basis of local adaptation
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Study site
• Pikas can be found along elevation gradients spanning over 1000 m in the central Coast mountains of BC,
• I have sampled Pikas from 5 populations along an altitudinal gradient in the Bella Coola valley, BC, Canada
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Study site
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Study site: The Hill~ 1500 m
~ 800 m
~ 300 m
2 km
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Study site: The Hill~ 1500 m
~ 800 m
~ 300 m
2 km
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Methods: Sampling
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Methods: Sampling
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Methods: Sampling
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Sampling: Hair snares
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Sampling: Hair snares
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Neutral genetic variation
Questions
• Is there evidence for gene flow between Pika populations sampled at different altitudes?
• Do populations from different elevations display signal of population declines?
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Neutral genetic variationAnalyzes
• 8 microsatellite loci
• Estimates of genetic diversity
• Estimates of population genetic structure
• Estimates of demographic history
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Neutral genetic variation
Preliminary results• 5 of 8 loci are polymorphic in this sample
• Pop n He Ho NaHigh 5 0.55 0.50 3.00Med 5 0.62 0.68 3.80Low1 4 0.50 0.50 2.80Low2 4 0.62 0.60 3.60Low3 4 0.60 0.65 3.60
Total/mean 22 0.58 0.59 3.36
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Neutral genetic variation
Preliminary results• Two individuals sampled at 155m intervals
had matching genotypes (PI = 0.02)
• Population structure analyzes: 5 clusters corresponding to each sampled population
• AMOVA indicates that 17% variation is found among populations
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Neutral genetic variation
Preliminary results
• Pairwise Fst
• No signal of population decline
Pop Med Low1 Low2 Low3High 0.17 0.17 0.18 0.07Med 0.17 0.18 0.24Low1 0.18 0.14Low2 0.13
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Adaptive genetic variationQuestions
• Can genomic scans identify regions underlying local adaptations in our samples?
• Can these markers be used to provide additional information about population genetic structure?
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Adaptive genetic variationAnalyzes
• AFLP genomic scans (20 primer combinations, 1177 bands)
• Detection of loci under selection
• Loci not under selection used to calculate:- Genetic diversity- Population structure
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Adaptive genetic variationPreliminary results
• Genomic scans detected 9.3% of loci potentially under selection (127/1177)
Fst
Genetic diversity
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Adaptive genetic variationPreliminary results
• Overall Genetic diversity
• Genetic differentiationMed Low1 Low2 Low3
High 0.022 0.091 0.073 0.053Med 0.035 0.035 0.019Low1 0.032 0.029Low2 0.012
Pop HjHigh 0.20679Med 0.27301Low1 0.31964Low2 0.33829Low3 0.32404
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Work in progress
Neutral genetic variation
• Genotype a large number of individuals(to be sampled this field season)
• Genotype 12 or more microsatellite loci
• Re-analyzes this dataset to provide final estimates of population genetic structure, and
demography
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Work in progressAdaptive genetic variation
• Identification of signature of selection in DNA sequences of targeted genes
• Identifying genes linked to outlier AFLPs detected
• Identification of the main selective forces driving Pika evolution
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Overall significance
• Assessment of demography and overall genetic health of pika populations
• Identifying important genes for adaptation
• Provide an assessment of the potential of pikas to survive in the face of climate change
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Acknowledgements
- Mary Peacock and her lab
- Kurt Galbreath
- Russello Lab
- Tweedsmuir Provincial Park Staff