Genetic differences on a local scale Testing Drosophila life-history in the field Paul M. Brakefield...
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Transcript of Genetic differences on a local scale Testing Drosophila life-history in the field Paul M. Brakefield...
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
Deforestation
The beginning…... …. and the end
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– ...
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?
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
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
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
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
Starvationresistance
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
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:
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
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
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
Subdivision into components
Genetic: 9 %Environmental: 58 %GxE interactions: 33 %
Field experiment 2: transplantation
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:
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
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
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
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
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