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Insect responses to heterogeneous (agricultural) plantscapes (in the tropics or elsewhere) Peter Hambäck

Department of Ecology, Environment and Plant Sciences

Local processes

Quantifying the patterns

• utside inside

shrubs

10 20 30 40 # egg per plant

0.01 0.1 1 10 1 10 100 1000

Density Host plant density

Otway et al. 2005 Hambäck et al 2000

0.1 1 10 100 100 1000 10000 Patch size Density

Välimäki & Itämies 2003

Density-area relationship DAR-slope Density-density relationship DDR-slope Log response ratio LRR

Responses depend on species traits

General responses to heterogeneity

• 2.0
• 1.5
• 1.0
• 0.5

0.0 0.5

• 1.0
• 0.5

0.0 0.5 1.0 Response to patch size (DARslope) Response to intercropping (lnRR)

• utside

inside shrubs

10 20 30 40 # egg per plant 10 20 30 40 # egg per plant 0.1 1 10 100 100 1000 10000 Patch size Density

Hambäck & Andersson unpubl

Andean potato weevils in relation to local and landscape features

Parsa et al. (2012) : PLoS ONE 7(5): e36533

Parsa et al. (2012) : PLoS ONE 7(5): e36533

Different source sizes

Parsa et al. (2012) : PLoS ONE 7(5): e36533

This year Last year Last year Last year Last year This year Last year

Different source sizes

Parsa et al. (2012) : PLoS ONE 7(5): e36533

Different target size

Parsa et al. (2012) : PLoS ONE 7(5): e36533

This year Last year This year Last year This year This year

Dilution effects

Parsa et al. (2012) : PLoS ONE 7(5): e36533

Different target sizes

Parsa et al. (2012) : PLoS ONE 7(5): e36533

This year Last year This year This year Patch size Number of immigrants Ln(Patch size) Ln(density) 1:1

Target size effects

10 100 1000 1 10 100 1000 Patch size Density

Eupteryx (Homoptera)

Zabel & Tscharntke 1998

0.1 1 100 1000 10000 100000 Patch size Density

Chiastocheta (Diptera)

Johannesen & Loeschcke 1996

0.1 1 10 100 100 1000 10000 Patch size Density

Parnassius (Lepidoptera)

Välimäki & Itämies 2003

Photo: Lars Ove Hansen Photo: Angela Schwartz Photo: Leonardo Melchionda

Response to spatial scale

Large, homogeneous and dense patches are high resource concentrations and attracts higher insect densities. Density is higher in large patches, for instance, because (Root 1973): Immigration is larger to large patches Emigration is larger from small patches

The resource concentration hypothesis

A modelling framework

Local density (n) Immigration (I) Emigration (En) birth mortality

I En rn dt dn + − =

β

ε

−

= A E

ζ −

= iA I

A stepwise process

Spatial distribution of plants Distribution

• f information

Herbivore perception Probability of locating plants Spatial distribution

• n herbivores

Insects have their traits

Insects may locate patches in different ways

Immigration rate depends on area e.g. aphids Immigration rate depends on perimeter e.g. carabids Immigration rate depends on diameter e.g. lepidopterans

Scaling the number of immigrants

Log(patch size) Log(immigration rate)

1:1

Effect on local density has different scaling

Log(patch size) Log(immigration rate)

Perimeter-to-area ratio Diameter-to-area ratio

• 1
• 0.5

0.5 Aphids (N=6) Beetles (N=6) Butterflies (N=31) Moths (N=3) Scaling coefficient

Observed immigration scalings

Including emigration

Local density (n) Immigration (I) Emigration (En) birth mortality

I En rn dt dn + − =

β

ε

−

= A E

ζ −

= iA I

Translating to density-area relationship

Log(patch size) Log(density)

emigration rate immigration rate

β > ζ β = ζ β < ζ

• 0.6
• 0.4
• 0.2

0.2 0.4 0.6 Aphids Leaf/planthoppers Beetles Butterflies Moths Flies

DARslope

Observations on DAR slopes

0.1 1 10 100 100 1000 10000 Patch size Density

• 0.6
• 0.4
• 0.2

0.2 0.4 0.6 Aphids Leaf/planthoppers Beetles Butterflies Moths Flies

DARslope

Observations on DAR slopes

Is difference in response due to differences in search modality?

How do olfactory searching insects experience their environment?

Measuring olfactory information

Andersson et al. In press

Measuring olfactory information

5 10 15 20 25 30 0.000 0.001 0.002 0.003 0.004

Time (s) Antennal response (mV

Quantifying olfactory information fields

10 20 30 40 50 60

• 0.0005

0.0005 0.0015

Time (s) Antennal response (mV

10 20 30 40 50 60

• 0.0005

0.0005 0.0015

Time (s) Antennal response (mV

1m 10m

60 70 80 90 100 110 120

• 0.0005

0.0005 0.0015

Time (s) Antennal response (mV

16m

10 20 30 40 50 60

• 0.0005

0.0005 0.0015

Time (s) Antennal response (mV

Control

Odor decay with distance

0.2 0.4 0.6 0.8 20 40 60 80

4 odor sources

0.2 0.4 0.6 0.8 20 40 60 80

9 odor sources

0.2 0.4 0.6 0.8 20 40 60 80

25 odor sources

Downwind distance (m)

Different patch sizes Different resource densities

• 1.5
• 1
• 0.5

0.5 1 1.5 Moths (10) Butterflies (2) Bugs (1) Plant lice (1) Leafhoppers (2) Aphids (18) Flies (7) Beetles (14)

• 1.5
• 1
• 0.5

0.5 1 1.5 Chrysomelidae (3) Curculionidae (8) Coccinellidae (3) Sphingidae (1) Pyralidae (3) Plutellidae (3) Noctuidae (3)

Scaling coefficient (DDRslope)

Observations on DDR slopes

0.01 0.1 1 10 1 10 100 1000

Density

• 1

Host plant density

0.01 0.1 1 10 1 10 100 1000

Density

• 1

Host plant density

Andersson et al. 2013. Oikos 122: 1009

Conclusions

Density patterns Feedback Environmental constraint Search modality A need for mechanistic studies connecting pattern to process

Acknowledgements

Petter Andersson Göran Englund Lia Hemerik Brian lnouye Marjolein Lof Christer Löfstedt Nora Underwood