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Artificial selection for aerial dispersal in the biocontrol predatory mite Phytoseiulus persimilis
Alexandra Revynthi, Dirk Verkleij, Arne Janssen & Martijn EgasIBED Department of Evolutionary and Population Dynamics
University of Amsterdam
(Photos: Jan van Arkel)
Phytoseiulus persimilis: a spider mite specialist
predatory mite
herbivorous mite
plant
overexploitation
overexploitation
Persistence in metapopulations: dispersal
Exploitation:“Dispersal‐during‐interaction” strategies?
• Killer‐strategy:no dispersal during predator‐prey interaction
• Milker‐strategy:some dispersal during predator‐prey interaction
Local Dynamics: Predator dispersal duringinteraction with prey
Killer Milkervan Baalen & Sabelis 1995
Predator dispersalallows prey to growand increases the production of predators.
Predator dispersal during interaction:
• Lower predation pressure
• Higher prey population growth
• More prey available
• Longer interaction period
• More predators dispersing to new patchesvan Baalen & Sabelis 1995
+
+
=
Longer interaction period
• Longer exposure to subsequent predator invasions.
• Invaders: will exploit the patch in their own interest(selfish way), ‘stealing’ the prey.
• Isolated sites favor the evolution of prudentpredators lower probability of co‐invasion.
van Baalen & Sabelis 1995
Milkers and Killers in Biocontrol
P. persimilis is used to control outbreaks of spider mites
Killers are essential for effective biocontrol WITHIN a patch of spider mites, especially ornamentals
Milkers may be desirable for effective biocontrol at a LARGER spatial scale, and/or crop plants
First Experimental evidence
Pels & Sabelis, 1999
“Killer line” “Milker line”
This project
Alexandra Revynthi collected strains from wild populations of P. persimilis
Experimental design Alexandra
This project
Alexandra Revynthi collected strains from wild populations of P. persimilis
6 locations in Turkey, 5 locations in Sicily
Significant differences in dispersal rate among strains
Variation in prey exploitation
Natural variation in dispersal strategies
Revynthi et al. (in prep.)Killers
MilkersCumulative number of dispersers
Step two:
If we cannot collectMilkers and Killers…
Can we select for the Milker and the Killer strategy?Artificial selection on timing of dispersal
Step two: artificial selection
Response to selection = heritability x selection differential
Selection differential is under experimenter’s control But without heritable variation NO response to
selection is expected…!
Potential problem: we did not measure heritability in our populations
Instead we mixed our populations base population
Experimental design Alexandra
Experimental design
Wind tunnels
Rose leaves (Rosa sp. var Avalanche)
Spider mites (T. urticae)
Predatory mites (P. persimilis)
Selection procedure
10 adult ♀ spider mites
Allow them to oviposit for 24h
60 ♀ adult predatory mites
One infested rose leaf trap
Observation every 2h for 8h, and 24h after the start of the experiment
2 rose leaves
Selection procedure
Select the first 20 dispersed predators x 6 = 120 ♀ Early Dispersal Line
Select the last 20 dispersed predators x 6 = 120 ♀Late Dispersal Line
A control line for each selection line: 120 random ♀ no selection
6 generations
Response experiment
80 spider mite eggs
30 ♀ adult predatory mites
One infested rose leaf trap
Observation every 2h for 8h
Count # of dispersers
rose leaf
Early dispersal and control lineX2 = 7.5, df = 1, P = 0.006
Late dispersal and control lineX2 = 8.7, df = 1, P = 0.003
Early vs Late dispersal control lineX2 = 0.42, df = 1, P = 0.516
Early vs Late dispersal lineX2 = 17.2, df = 1, P << 0.001
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Time (Days)
Cumulative num
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Early‐dispersal
Late‐dispersal
Population Dynamics experiment
Conclusions
Dispersal tendency was affected by imposed selection
Timing of dispersal is a heritable trait
It is possible to select for Milkers and Killers
Implications
Killer predator line is good for effective LOCAL biocontrol, especially in ornamentals
Milker predator line is good for effective GLOBAL biocontrol, especially in crop plants
Breeding programsmites with high or low innate tendency to disperse – genetically fixed
Thank you for your attention!
Arne JanssenDirk VerkleijAlexandra Revynthi
NEW: the Netherlands Society for Evolutionary Biology!
Website: NLSEB.NL
First meeting: April 11th in Ede (NL)
Evolution in the broadest sense, and including evolutionary applications
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Rearing set‐up
Response experiment
4 replicates of selection line
4 replicates of control line
3 blocks (replicates of the experiment)
Survival analysis
} In each block
Response experiment overallX2 = 20.4, df = 3, P = 0.0001
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