Changing habitats, changing populations?

1
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
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Life cycle of a Drosophila
Between 9 and 15 days.
Up to gt30 days.
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A life history trade-off and community structure
in variable environments.

• 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!

• Sevenster JG van Alphen JJM (1993) Lecture
  notes in Biomatics 98 155-172.
• Sevenster JG van Alphen JJM (1993) Journal of
  Animal Ecology 62 720-736.

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Graphical representation
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Philippines 1994

• Are there differences between habitats?
• Does the habitat shape the realized trade-off
  between the traits?

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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.

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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
  F1 generation.
• Measuring development time and starvation
  resistance F2 generation.

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Starvation resistances
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Development times
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Monte-carlo simulation
Observed value
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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 (p1.0).
• Effect of the environment on the expression of
  development time and starvation resistance
  unknown.

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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.

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Common environment versus real environment
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Panama 1998

• 1 Expression of life-history traits in the
  original habitat
• 2 Transplantation experiment, offspring of many
  females
• 3 Transplantation experiment, offspring of a
  single female
• 4 Common environment in the lab in Leiden

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Unfortunately, the results are not yet available.
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Genetic correlation's in D. melanogaster
Development time


0
0
Body size

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Longevity


Starvaton resistance / fat content
Source Zwaan, BJ (1993) Genetical and
environmental aspects of aging in Drosophila
melanogaster. Ph.D. thesis, Groningen