An analysis of sexual selection using Bateman’s
principles on a giant water bug (Abedus herberti)
with paternal care
Marshall Knoderbane and David Lytle
Department of Zoology, OSU
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.
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
Introduction: Bateman’s Principles
Classic sex-roles
Males have:
Higher variance in
reproductive success
Higher variance in
mating success
Steeper Bateman
gradient
Arnold 1994 Am. Nat.
Reproductive Success
(Number of Offspring)
80
70
Males
60
50
40
30
Females
20
10
0
0
1
2
3
Mating Success
(Number of Mates)
4
5
Introduction: Bateman’s Principles
Sex-role reversed
High paternal
investment limits male
reproductive success
Reproductive Success
(Number of Offspring)
80
Females
70
60
50
40
Males
30
20
10
0
0
1
2
3
4
Mating Success
(Number of Mates)
Do female A. herberti experience stronger selection
than do males (i.e. have a steeper Bateman Gradient)?
5
Methods: Study site
East Turkey Creek and the American Museum of Natural History’s
Southwest Research Station in the Chiricahua Mountains
Methods: Experimental design
2006
n=86 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
+6
6
Females
=
Males
In One Tank
One
Replicate
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 A&M)
Results
Optimization of primer performance
Two replicates microcosms genotyped
Preliminary Results
Reproductive Success
140 n=6
vriance=1977.2
120
n=36
variance=1176.0
100
80
60
40
20
0
Females
Males
Mating Success
4 n=6
variance=1.767
Mating Success
Similar variance in
Reproductive and
Mating Success
Little sexual
dimorphism
No female
preference for
males brooding
eggs
Reproductive Success
3
?
2
1
0
Females
Males
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
Acknowledgements
Asako Yamamuro
Arlo Pelegrin
Laura McMullen
Kate Boersma
Deb Finn
SWRS Staff & Volunteers
Tessa Biboux
Funding:
NSF REU
Vindhya Amarasinghe
Ivan Phillipsen
OSU URISC
OSU HHMI
COS Cripps Scholarships
Mike Blouin
Kaitlin Bonner
Jacob Tennessen
Photo Credits
Frog-www.pictopia.com
Elk-www.hickerphoto.com
Widowbird-www.arthistory.about.com
Wolf-www.sports.espn.go.com