Costs of immune defence in a wild damselfly population

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Costs of immune defence in a wild damselfly
population
Rantala, M. J., Honkavaara, J. Suhonen, J.
Department of Biology, University of Turku,
Finland
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Introduction

• The central tenet of ecological immunology is
  that the resistance against parasites and
  pathogens are costly for the host.

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Introduction

• The central tenet of ecological immunology is
  that the resistance against parasites and
  pathogens are costly for the host.
• There are three main types of costs to immune
  defence

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Introduction

• The central tenet of ecological immunology is
  that the resistance against parasites and
  pathogens are costly for the host.
• There are three main types of costs to immune
  defence
• The costs associated with maintaining/investing
  in constitutive immune function.

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Introduction

• The central tenet of ecological immunology is
  that the resistance against parasites and
  pathogens are costly for the host.
• There are three main types of costs to immune
  defence
• The costs associated with maintaining/investing
  in constitutive immune function.
• The costs of producing an induced response to an
  immune insult.

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Introduction

• The central tenet of ecological immunology is
  that the resistance against parasites and
  pathogens are costly for the host.
• There are three main types of costs to immune
  defence
• The costs associated with maintaining/investing
  in constitutive immune function.
• The costs of producing an induced response to an
  immune insult.
• The cost of evolving immunity.

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The costs of immunity
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Why it is important to study the cost of immunity
in wild population?

• Conspecific and interspecific competitors
• Parasites and pathogens
• Varying environment...
• Predators

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Aims of the study 1.

• Does activation of immune system affect
  predation risk, survival and territorial
  behaviour?

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Territoriality

• Two and/or three mating strategies
• Territorial
• Non-territorial
• (Switcher)
• Territorial males have higher mating success than
  non-territorial.

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Study area Tarvasjoki Creek
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Immune activation Methods

• 6 nesting pairs of white wagtails (Motacilla
  alba)
• 13 slaughter stations

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Immune activation Methods

• Collected after their maiden fly
• Marked with silver pen
• Three groups
• implanted with a nylon monofilament (n190)
• sham-manipulated, wounded (n176)
• Control (n181)
• Released back to the river

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Methods

• Controlled daily
• Monitored territorial behavior
• Monitored wagtail hunting and collected wings of
  killed damselflies
• Controlled for dispersal

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Immune activation Territoriality
?2 11.4 df 2 p 0.003
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Predation

• More than one third of the males (207 out of 546
  males, 38) were depredated by birds

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Activation of immune systemincreased predation
risk
?2 10.0 df 2 p 0.007
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Immune activation

• Linear logit model
• G2 0.401
• df 2
• P 0.818

Territorial behavior decreased and immune
activation increased avian predation risk
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Immune activation Survival
GLM F 2,544 8.29 P 0.003
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Conclusions

• Immune-challenged males
• - less frequently territorial
• - increased predation risk
• - lower overall survival
• Activation of immune system is costly!

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Aims of the study 2.

• Is individual variation in immunity related to
  predation risk and survival?

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Individual variation Methods

• Males collected 6th and 14th June (n157)
• Taken to laboratory
• body mass, hind wing length and wing spot size
  measured
• implanted, incubated for 20 hours, implant
  removed
• Released back to the river

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Individual variation
Predated by birds Not predated by birds
First period (6th June)
Second period (14th June)
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Individual variation EncapsulationLogistic
regression model probability to be predated by
bird in relation to encapsulation response
82 of cases correctly predicted
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Conclusions

• Predators prey on individuals of inferior
  phenotypic quality!
• Predation may cause substantial selection
  pressure on immunity and may shape trade-offs
  between immunity and life history traits.

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Acknowledgements

• Field assistants Henna Aalto, Jaakko Ilvonen,
  Katariina Kangassalo, Kari Kaunisto, Janne
  Kumpulainen, Topias Laaksonen, Kalle Laitila,
  Pipsa Lappalainen, Urzula Malinkowska, Lauri
  Rantanen, Eeva Rönnholm, Teijo Saikkonen, Anna
  Sipilä, Anssi Susilahti, Sini Tuomola and Heidi
  Viitaniemi
• Funding Academy of Finland

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Thank you!