Genetic differences on a local scale Testing Drosophila life-history in the field Paul M. Brakefield Jan G. Sevenster Jacques J.M. van Alphen Bas 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 ( ), Krijger ( ) –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, individuals

Starvation resistance

Overall variation 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 SSFreedom MS F p Intercept Transect Origin (OR) Experimental (EX) <0.001 Transect*OR <0.001 Transect*EX OR*EX <0.001 Transect*OR*EX <0.001 Error Degree of SSFreedom MS F p Intercept Transect Origin (OR) Experimental (EX) <0.001 Transect*OR <0.001 Transect*EX OR*EX <0.001 Transect*OR*EX <0.001 Error Field experiment 2: transplantation

Original versus experimental habitat Field experiment 2: transplantation

Subdivision into components 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 variation Common environment experiment

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

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 Testing Drosophila life-history theory in the field: local adaptation in body size, development time and starvation resistance. Ph.D.-Thesis. Leiden university, Leiden