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How do Long-range Insect Migrants Control their Flight Direction? Jason W. Chapman Rothamsted Research, UK
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Transcript of How do Long-range Insect Migrants Control their Flight ... · How do Long-range Insect Migrants ....

  • How do Long-range Insect Migrants Control their Flight Direction?

    Jason W. ChapmanRothamsted Research, UK

  • Introduction

    Class Species Location Numbers Biomass (tons)Insects Darner Dragonfly Argentina 4 6 Billion 4000

    Monarch Mexico 200 Million 80Desert Locust North Africa 109 1011 200,000

    Mammals Wildebeest East Africa 1.3 million 280,000Free-tailed Bat New Mexico 20 million 300

    Holland, Wikelski & Wilcove (2006) How and why do Insects Migrate? Science

    1. Enormous Numbers and Biomass

    3. Simple Systems and Model Organisms

    2. Crop Pests and Disease Vectors Orthoptera (e.g. locusts) Hemiptera (aphids & planthoppers) Lepidoptera (armyworms, cutworms & bollworms) Diptera (mosquitoes, midges & blackflies) Coleoptera (bark beetles)

  • Biometeorology of Migration

    Weather hugely influential on insect migration patterns Wind speed & direction

    Airspeeds of large insects about 3 6 ms-1

    Airspeeds of micro-insects often

  • Seasonal Migration Patterns

    Most insect migration is one-way

    Return movements, if any, carried out by subsequent generations

    Much movement nomadic by nature, but there are general directional trends In tropical & sub-tropical regions, movements related to rainfall In temperate regions, there is a tendency for north-south seasonal movements

    Movements over the necessary distances requires favourable winds Poleward winds in the spring are warm and thus favourable for migration Equatorward winds are cool and so will tend to suppress migration

    Led to the idea of the Pied Piper effect

    Largely discounted now, return movements have been documented in many species

    Natural selection may be expected to act very strongly on the autumn migration

  • Do Simple Rules Guide Migrations?

    Selection of Favourable Winds in Green Darner Dragonflies in the Autumn

    Wikelski et al (2006) Simple Rules Guide Dragonfly Migration. Biology Letters

    Green Darner Dragonflies Anax junius Christian Ziegler

    Migrate on days following cooler nights Fly downwind (tend to be northerlies, so southward movement) Re-orientated when faced with large water crossing Simple rules (like songbirds)

  • Monarch Time-compensated Solar Compass

    Danaus plexippus

    Mouritsen & Frost (2002) Virtual Migration in Tethered Flying Monarch Butterflies Reveals their Orientation Mechanisms. PNAS

  • Return Migration of Vanessa cardui

    Painted Lady Vanessa cardui Ian Woiwod

    Annual immigrant to UK from N Africa

    Varying abundance

    Good years: 1996, 2000, 2003, 2006

    Evidence for return migrations?

    Rebecca Nesbit

    Nesbit, Hill, Sivell, Woiwod & Chapman (in prep)

  • Flight simulators in Gibraltar May 2006 Ian WoiwodPainted Lady Ian Woiwod

    Flight Simulators

    Mouritsen & Frost (2002) PNAS 99: 10162-10166

  • Orientation of Autumn MigrantsRebecca Nesbit

    N = 94 individualsR = 0.32Mean direction = 193P < 0.001

    Clear Skies

    N = 27 individualsR = 0.09No mean directionP = 0.813

    Overcast Skies

    Nesbit, Hill, Sivell, Woiwod & Chapman (in prep)

  • Time Compensation?Rebecca Nesbit

    N = 94 individualsR = 0.32Mean direction = 193P < 0.001

    Control Group

    N = 26 individualsR = 0.46Mean direction = 180P < 0.001

    Clock-shifted

    Nesbit, Hill, Sivell, Woiwod & Chapman (in prep)

  • Flight Towards the Sun?Rebecca Nesbit

    Nesbit, Hill, Sivell, Woiwod & Chapman (in prep)

  • Vertical-Looking Radar (VLR)

    Continuous coverage:150 1200 m

    Individual insects:15 height bands

    Parameters:Speed & direction

    OrientationMassShape

    0 m

    600 m

    1200 m

    5 mg

    15 mg

    1 mg

    500 mg

    Chapman et al (2003) Vertical-looking Radar: A New Tool for Monitoring High-altitude Insect Migration. Bioscience

  • Orientation Mechanisms in High-flying Moths

    Silver Y Autographa gamma

    Annual migrant to N Europe from Med

    Flies at heights of 200 m 1000 m

    Layers correspond to regions of wind speed maxima

    Can it have any control over its displacement direction?

    Chapman et al (2008a) Wind Selection and Drift Compensation Optimize Migratory Pathways in a High-flying Moth. Current Biology

    Chapman et al (2008b) A Seasonal Switch in Compass Orientation in a High-flying Migrant Moth. Current Biology

  • Spring Migration Events

    Displacement Directions

    N = 83 Events (20,000+ moths)Mean Direction = 354R = 0.66P < 0.001

    Wind Directions

    N = 108 eventsMean Direction = 197R = 0.29P < 0.001

    FlightHeadings

    N = 78 Events (20,000+ moths)Mean Direction = 18R = 0.17P < 0.001

    Chapman et al (2008a) Current Biology 18: 514-518Chapman et al (2008b) Current Biology 18: R908-909

  • Autumn Migration EventsDisplacement

    Directions

    N = 96 Events (38,000+ Moths)Mean Direction = 169R = 0.39P < 0.001

    Wind Directions

    N = 121 EventsNo Mean DirectionR = 0.12P = 0.15

    Flight Headings

    N = 96 Events (38,000+ Moths)Mean Direction = 195R = 0.24P < 0.001

    Chapman et al (2008a) Current Biology 18: 514-518Chapman et al (2008b) Current Biology 18: R908-909

  • Trajectory AnalysesLaura Burgin

    Met Offices NAME Dispersion Model

  • Displacements HeadingsCompass-mediatedOrientation in Other Species

    Large Yellow Underwing Noctua pronuba

    Chapman et al (in prep)

  • Concluding Remarks

    Not passive or accidental movements

    Central role for behaviour

    Complicated & sophisticated strategies

    Behaviour often inferred from observations of migration patterns

    Need for experimental approaches

  • Acknowledgements

    Ian Woiwod, Alan Smith, Joe Riley, Duncan Sivell, Rebecca Nesbit (Rothamsted)

    Don Reynolds (University of Greenwich)

    Henrik Mouritsen (University of Oldenburg)

    Jane Hill (University of York)

    Curtis Wood, Janet Barlow (University of Reading)

    Laura Burgin, Peter Clark (Met Office)

    Funding (BBSRC)

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