An analysis of sexual selection using Bateman

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An analysis of sexual selection using Batemans
principles on a giant water bug (Abedus herberti)
with paternal care
Marshall Knoderbane and David Lytle Department of
Zoology, OSU
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Introduction An unlikely bug

• Belostomatids
• Large
• Long lived
• Apex predators
• Few offspring
• Iteroparous
• Exclusive paternal care

Paternal care is rare, occurring in just 13
arthropod taxa
Tallamy 2001 Annu. Rev. Entomol.
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Introduction Sexual selection
Differential reproductive success due to
variation in mating success
Parental investment heavily impacts the strength
and direction of sexual selection
Bateman 1948 Heredity Trivers 1972
Analysis of selection important in understanding
evolution of paternal care
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Introduction Batemans Principles Classic
sex-roles

• Males have
• Higher variance in reproductive success
• Higher variance in mating success
• Steeper Bateman gradient

Arnold 1994 Am. Nat.
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Introduction Batemans Principles Sex-role
reversed
High paternal investment limits male reproductive
success
Do female A. herberti experience stronger
selection than do males (i.e. have a steeper
Bateman Gradient)?
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Methods Study site
East Turkey Creek and the American Museum of
Natural Historys Southwest Research Station in
the Chiricahua Mountains
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Methods Experimental design 2006

• n86 water bugs assigned to six replicate
  microcosms
• Environmental conditions keep nearly normal
• Allowed to mate for 21 days
• Allowed to hatch for 27 days (sexes separate)
• Paternity of nymphs was recorded

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Methods Parentage analysis 2008

• Amplification of eight microsatellite loci using
  PCR
• Genotyped four replicates microcosms
• All parents
• Subsample of 30 offspring/male
• Analysis with Cervus and Gerud (Adam Jones, Texas
  AM)

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Results

• Optimization of primer performance
• Two replicates microcosms genotyped

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Preliminary Results

• Similar variance in Reproductive and Mating
  Success
• Little sexual dimorphism
• No female preference for males brooding eggs

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Conclusions
Though parental investment can heavily impacts
the strength and direction of sexual selection,
A. herberti may be not be sex-role reversed
and/or not under sexual selection
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Acknowledgements

• Funding
• NSF REU
• OSU URISC
• OSU HHMI
• COS Cripps Scholarships

Vindhya Amarasinghe Ivan Phillipsen
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Photo Credits

• Frog-www.pictopia.com
• Elk-www.hickerphoto.com
• Widowbird-www.arthistory.about.com
• Wolf-www.sports.espn.go.com