Changing habitats, changing populations? Life-history evolution of coexisting Drosophila species in a heterogeneous environment. Institute for Evolutionary and Ecological Sciences, Section Animal Ecology and Section Evolutionary Biology, Leiden University, Leiden, The Netherlands. Paul Brakefield Jan Sevenster Bas Zwaan Kim van der Linde

16 March 1999Changing habitats, changing populations? 2 Life cycle of a Drosophila Between 9 and 15 days.Up to >30 days.

16 March 1999Changing habitats, changing populations? 3 A life history trade-off and community structure in variable environments. Sevenster JG & van Alphen JJM (1993) Lecture notes in Biomatics 98: Sevenster JG & van Alphen JJM (1993) Journal of Animal Ecology 62: The availability of a certain resource in the environment varies through the year. Species differ in life-history. A short development time is an advantage when fruit is abundant. A good starvation resistance (survival time under food stress) is an advantage when fruit is scarce. A trade-off between development time and starvation resistance allow different species to have a competitive advantage during different times of the year!

16 March 1999Changing habitats, changing populations? 4 Graphical representation

16 March 1999Changing habitats, changing populations? 5 Philippines 1994 Are there differences between habitats? Does the habitat shape the realized trade-off between the traits?

16 March 1999Changing habitats, changing populations? 6 Different habitats Habitats differ in year round breeding substrate availability. Local populations are likely to adapt to those differences. Expected result is that populations of the same species from different habitats will show differences in the life-history traits.

16 March 1999Changing habitats, changing populations? 7 Methods Collecting flies from four habitats: secondary forest, forest edge, kaingin (slash and burn agriculture) and grassland: P generation. Bring them to the common environment of the lab: F 1 generation. Measuring development time and starvation resistance: F 2 generation.

16 March 1999Changing habitats, changing populations? 8 Starvation resistances

16 March 1999Changing habitats, changing populations? 9 Development times

16 March 1999Changing habitats, changing populations? 10 Monte-carlo simulation Observed value

16 March 1999Changing habitats, changing populations? 11 Pilot experiment (Philippines, 1994) Conclusions: –There is variation between habitats in both traits for several species. –Concordant effect of habitat on development time (8 species, monte carlo simulation, p=.028). –Variation has the same pattern for all (7) species of the Sophophora subgenus (p=.0012). –No effect on starvation time (p=1.0). –Effect of the environment on the expression of development time and starvation resistance unknown.

16 March 1999Changing habitats, changing populations? 12 Questions? How are life-history traits expressed under natural circumstances? Are there genetic correlations that can pose a barrier to ecological optimisation? How do ecological and genetic aspects of life-history variation among and within species relate to properties of the natural habitats? Evaluate theory on the relationship between life-history trade-offs and coexistence and community structure in heterogeneous environments.

16 March 1999Changing habitats, changing populations? 13 Common environment versus real environment

16 March 1999Changing habitats, changing populations? 14 Panama Expression of life-history traits in the original habitat 2Transplantation experiment, offspring of many females 3Transplantation experiment, offspring of a single female 4Common environment in the lab in Leiden

16 March 1999Changing habitats, changing populations? 15 Unfortunately, the results are not yet available.

16 March 1999Changing habitats, changing populations? 16 Genetic correlation's in D. melanogaster Development time Body size Longevity Starvaton resistance / fat content ±0 Source: Zwaan, BJ (1993) Genetical and environmental aspects of aging in Drosophila melanogaster. Ph.D. thesis, Groningen +