genetic differences on a local scale testing drosophila life-history in the field paul m. brakefield...
DESCRIPTION
Habitat change: local effects Abiotic: microclimatic changes –Higher day temperatures –Dryer –Higher light intensity at the forest floor –... Biotic –Vegetation composition and structure –Resource abundance –Species composition –...TRANSCRIPT
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Genetic differences on a local scale
Testing Drosophila life-history in the field
Paul M. BrakefieldJan G. SevensterJacques J.M. van AlphenBas J. Zwaan
Leiden University,Institute for Biology,Sections Animal Ecology & Evolutionary Biology,The Netherlands.
Kim van der Linde
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Deforestation
The beginning…... …. and the end
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Habitat change: local effects
• Abiotic: microclimatic changes– Higher day temperatures– Dryer– Higher light intensity at the forest floor– ...
• Biotic– Vegetation composition and structure– Resource abundance– Species composition– ...
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Research questions
• Does variation between habitats over short distances result in local adaptation in the resident populations?
• And if so, what is the relative importance of:– Genetic differences?– Environmental variation?– GxE interactions?
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Where?• Panama canal zone
– Easy access– Established situation
• Two transects with each three habitats:– Forest– Intermediate– Grassland
• Distance between habitats within a transect 1-2 km• Distance between transects 10 km
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Which model system?• Panamanian Drosophila
– Ecologically well studied: Sevenster (1987-1992), Krijger (1996-2000)
– Many species:30+ within Panama canal zone, 12 used in this experiment• Elimination of lucky choice• Robustness of effect
– Short generation time: 8-15 days
– Easy to collect and culture
• Three ecological relevant life-history traits– Body size– Development time– Starvation resistance
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Field set-up
• Large roofed cages to work in• Small cages with fine netting for development times• Petridishes with agar and covered with fine netting for
starvation resistance• Dead flies for body size
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Experiments• Collection of flies
– Maintained in open air laboratory for several generations
• Field experiment 1: expression of life-history traits in the original collection habitat– 12 species, 5941 individuals
• Field experiment 2: transplantation experiment– 4 species, 5629 individuals
• Common environment experiment: expression of life-history traits in the laboratory environment– 12 species, 15802 individuals
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Starvationresistance
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Overall variation
Maria transect
Summit transect
Habitat: F(2, 2921) = 9.2673, p < 0.001
Transect: F(1, 2921) = 0.41939, p = 0.52
Location (habitat*transect): F(2, 2921) = 10.569, p < 0.001
Original AND experimental habitat
Sta
rvat
ion
resi
stan
ce re
sidu
als
-0.20
-0.15
-0.10
-0.05
0.00
0.05
0.10
0.15
0.20
Forest Intermediate Grassland
Field experiment 1: original environment
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Conclusions
• First field experiment (original environment):– Habitat and location effect on starvation resistance– Forest populations do better then grassland populations
• Second field experiment (transplantation experiment):• Common environment experiment:
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Transect 2
Forest Inter-mediate
Grass-land
Transect 1
Forest Inter-mediate
Grass-land
Experiment
Transect 2
Forest Inter-mediate
Grass-land
Transect 1
Forest Inter-mediate
Grass-land
Stocks
Field experiment 2: transplantation
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Degree of SS Freedom MS F p
Intercept .0673 1 .067 .330 0.56Transect 1.3706 1 1.370 6.730 0.01Origin (OR) .8766 2 .438 2.152 0.12Experimental (EX) 26.9426 2 13.471 66.157 <0.001Transect*OR 3.4590 2 1.729 8.493 <0.001Transect*EX 1.1549 2 .577 2.835 0.06OR*EX 8.6395 4 2.159 10.607 <0.001Transect*OR*EX 7.3454 4 1.836 9.018 <0.001Error 593.5638 2915 0.203
Degree of SS Freedom MS F p
Intercept .0673 1 .067 .330 0.56Transect 1.3706 1 1.370 6.730 0.01Origin (OR) .8766 2 .438 2.152 0.12Experimental (EX) 26.9426 2 13.471 66.157 <0.001Transect*OR 3.4590 2 1.729 8.493 <0.001Transect*EX 1.1549 2 .577 2.835 0.06OR*EX 8.6395 4 2.159 10.607 <0.001Transect*OR*EX 7.3454 4 1.836 9.018 <0.001Error 593.5638 2915 0.203
Field experiment 2: transplantation
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Original versus experimental habitat
MariaEugenia
SummitGardens
Experimental habitat
-0.3
-0.2
-0.1
0.0
0.1
0.2
0.3
ForestIntermediate
Grassland
Original habitat
Sta
rvat
ion
resi
stan
ce re
sidu
als
-0.3
-0.2
-0.1
0.0
0.1
0.2
0.3
ForestIntermediate
Grassland
Field experiment 2: transplantation
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Subdivision into components
Genetic: 9 %Environmental: 58 %GxE interactions: 33 %
Field experiment 2: transplantation
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Summary of conclusions• First field experiment (original environment):
– Habitat and location effect on starvation resistance– Forest populations do better then grassland populations
• Second field experiment (transplantation):– Strong environmental impact– Original by experimental location effect indicates gxe
interaction for 4 species at population level• Common environment experiment:
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Overall variationCommon environment experiment
MariaEugenia
SummitGardens
Habitat: F(2, 9040) = 10.872, p < 0.001
Transect: F(1, 9040) = 25.092, p < 0.001
Location (habitat*transect): F(2, 9040) = 2.5096, p = 0.08
Original habitat
Sta
rbat
ion
resi
stan
ce re
sidu
als
-0.20
-0.15
-0.10
-0.05
0.00
0.05
0.10
0.15
0.20
Forest Intermediate Grassland
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Summary of conclusions• First field experiment (original environment):
– Habitat and location effect on starvation resistance– Forest populations do better then grassland populations
• Second field experiment (transplantation):– Strong environmental impact– Original by experimental location effect indicates GxE interaction for 4
species at population level
• Common environment experiment:– Habitat and location related genetic differences– Grassland population are better adapted to stress
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Variation in thefield?
Variation in thelaboratory?
GeneticEnvironmentalGxE
Body size Yes, butinconsistent
Yes, andconsistent atlocation level
32.7%35.8 %31.4 %
Developmenttime
Yes, andconsistent atlocation level
Yes, andconsistent atlocation level
19.8 %40.9 %39.4 %
Starvationresistance
Yes, andconsistent athabitat level
Yes, andconsistent athabitat level
9.0 %58.0 %33.0 %
Variation in thefield?
Variation in thelaboratory?
GeneticEnvironmentalGxE
Body size Yes, butinconsistent
Yes, andconsistent atlocation level
32.7%35.8 %31.4 %
Developmenttime
Yes, andconsistent atlocation level
Yes, andconsistent atlocation level
19.8 %40.9 %39.4 %
Starvationresistance
Yes, andconsistent athabitat level
Yes, andconsistent athabitat level
9.0 %58.0 %33.0 %
Comparison with other traits
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Final conclusions
• Local adaptation does take place
• The results are robust and are duplicated between species
• Extensive GxE interaction present in all three traits
• Extrapolating the results from one common environment to general conclusions about the field is tricky
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Questions?
• van der linde, K. 2003. Testing Drosophila life-history theory in the field: local adaptation in body size, development time and starvation resistance. Ph.D.-Thesis. Leiden university, Leiden