bite force

Report
Determinants of mating success in lizards.
Huyghe Katleen
Functional Morphology lab
University of Antwerp
variation
among species
variation
among species
NATURAL SELECTION
variation in environment
≠ lizard species
variation
within species, between sexes
SEXUAL SELECTION
= environment, ≠ sexes
male secondary sexual traits
sexual selection
sexually selected
design
sexually selected
performance
fitness
(reproductive
success)
sexual selection
male secondary sexual traits
female choice
male-male competition
sexual selection
male secondary sexual traits
signals
Residual bite force (N)
Anolis lineatopus
Residual dewlap area (mm²)
Vanhooydonck et al. 2005 Funct. Ecol.
sexual selection
male secondary sexual traits
signals
Crotaphytus collaris
Lappin et al. 2005 Am. Nat.
sexual selection
intrasexually
selected design
intrasexually
selected
performance
intersexually
selected design
intersexually
selected
performance
??
fitness
(reproductive
success)
study species
big ≠ between males & females
male
Lacerta vivipara
female
female
female
female
male
male
Gallotia galloti
Podarcis melisellensis
intrasexual selection
intrasexual selection
slowed down 2 x...
intrasexual selection
intrasexually
selected design
intrasexually
selected
performance
?
fitness
(reproductive
success)
intrasexual selection
determinants of fighting ability
Differences between winners and losers
20
p = 0.01
15
10
p = 0.13
5
p = 0.65
p = 0.73
0
-5
-10
sprint speed
endurance
acceleration
bite force
Gallotia galloti
intrasexual selection
D iffe re n ce s b e tw e e n w in n e rs an d lo se rs
determinants of fighting ability
Podarcis melisellensis
0 .1 0
p = 0.028
0 .0 8
0 .0 6
p = 0.029
0 .0 4
0 .0 2
p = 0.21
0 .0 0
-0 .0 2
-0 .0 4
-0 .0 6
-0 .0 8
b o d y co n d itio n
b ite fo rce
ve lo city
intrasexual selection
D iffe re n ce s b e tw e e n w in n e rs an d lo se rs
determinants of fighting ability
Podarcis melisellensis
0 .1 0
p = 0.028
0 .0 8
0 .0 6
p = 0.029
0 .0 4
0 .0 2
p = 0.21
0 .0 0
-0 .0 2
-0 .0 4
-0 .0 6
-0 .0 8
b o d y co n d itio n
b ite fo rce
ve lo city
intrasexual selection
determinants of fighting ability
bite
force
+
+
body
condition
fighting
ability
intersexual selection
intersexually
selected design
intersexually
selected
performance
?
fitness
(reproductive
success)
intersexual selection
males out
intersexual selection
partition out
intersexual selection
female in
intersexual selection
determinants of female preference
Podarcis melisellensis
intersexual selection
D ifferen ces b etw een p referred an d n o n -p referred
determinants of female preference
Podarcis melisellensis
0 .1 0
0 .0 8
0 .0 6
p = 0.033
0 .0 4
0 .0 2
p = 0.017
0 .0 0
p = 0.079
-0 .0 2
-0 .0 4
-0 .0 6
-0 .0 8
b o d y co n d itio n
b ite fo rce
ve lo city
intersexual selection
D ifferen ces b etw een p referred an d n o n -p referred
determinants of female preference
Podarcis melisellensis
0 .1 0
0 .0 8
0 .0 6
p = 0.033
0 .0 4
0 .0 2
p = 0.017
0 .0 0
p = 0.079
-0 .0 2
-0 .0 4
-0 .0 6
-0 .0 8
b o d y co n d itio n
b ite fo rce
ve lo city
sexual selection
Podarcis melisellensis
bite
force
+
fighting
ability
+
body
condition
+
trade off!
female
preference
sexual selection
Podarcis melisellensis
bite
force
+
fighting
ability
+
body
condition
+
??
female
preference
mating
success
Lacerta vivipara
Study species
• Common lizard (Lacerta vivipara)
• Polygynandrous mating system
• Female and male mate choice (intersexual selection)
• Male biased sex-ratio has deleterious effect on females
 severe biting during copulation  mating scars
© wild about Britain
Lacerta vivipara
 conflicting demands of sexes
 differential predictions for sexually selected traits
 cf. sexual selection?
 intrasexual competition
 traits increasing dominance
 size, running speed, bite force capacity?
male
 intersexual selection
 traits preferred by females
 reproduction vs survival in females!
female
Lacerta vivipara
Spanish Pyrenees (Roncesvalles)
March 2010, @ female emergence
15 virgin females & 45 adult males
France
Spain
experimental set-up
3hr
Lacerta vivipara
heating rock
3 males
1 female
hide
experimental set-up
3hr
males
• = size
• = tail type
heating rock
3 males
1 female
hide
•
•
•
•
mass
tail length
maximal bite force
maximal sprint speed
• Mating order
• Copulation time
• Behaviour (approaches, bites)
mated vs. unmated
TAIL LENGTH
yes
mated
yes
no
120
Tail length (mm)
100
80
60
40
20
F1,25 = 5.82
p = 0.024
0
0
2
4
6
8
10
12
Mategroup
Tail length mated > unmated !!
14
16
mated vs. unmated
SPRINT SPEED
NO
140
mated
yes
no
S p rin t sp e e d (cm /s)
130
120
110
100
90
F1,25 = 1.57
p = 0.22
80
70
0
2
4
6
8
10
12
M a te g ro u p
Sprint speed mated = unmated
14
16
mated vs. unmated
BITE FORCE
Yes, but…
2.0
mated
yes
no
1.5
Residual Bite Force
1.0
0.5
0.0
-0.5
-1.0
F1,24 = 7.04
p = 0.014
-1.5
-2.0
0
2
4
6
8
10
12
Mategroup
Bite Force mated < unmated !!
14
16
mating order
TAIL LENGTH
yes
120
mating order
1
2
3
0
Tail length (mm)
100
80
60
40
20
F1,25 = 6.26
p = 0.019
0
0
2
4
6
8
10
Mategroup
Long tails mate first!!
12
14
16
mating order
SPRINT SPEED
NO
140
mating order
1
2
3
0
S p rin t sp e e d (cm /s)
130
120
110
100
90
F1,25 = 3.50
p = 0.073
80
70
0
2
4
6
8
10
12
14
16
M a te g ro u p
Mating order not determined by sprint speed
mating order
BITE FORCE
Bite Force Capacity (N)
8
7
6
5
4
3
-2.0
-1.5
-1.0
-0.5
0.0
Head size
0.5
1.0
1.5
2.0
mating order
BITE FORCE
Yes, but…
8
unmated males
Bite Force Capacity (N)
mating order
1
2
3
0
7
6
first mated
5
4
F1,24 = 9.57
p = 0.005
3
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Head size
Mating order determined by bite force capacity!!
mating behaviour
• # approaches to other males
• # bites to other males
• # approaches to female
• copulation time
NOT determined by
• tail length
• sprint speed
• bite force
(F1,12 = 0.34, p = 0.57)
(F1,12 = 0.32, p = 0.58)
(F1,12 = 2.80, p = 0.12)
• mating order
(F1,12 = 3.70, p = 0.079)
in short…
bite
force
-
mating
success
tail
length
+
overall results
bite
force
+
fighting
ability
+
+
body
condition
tail
length
+
mating
success
female
preference
+
+
overall results
bite
force
+
fighting
ability
+
body
condition
tail
length
+
+
trade off!
mating
success
female
preference
+
+
discussion
bite
force
+
fighting
ability
+
body
condition
tail
length
+
+
trade off!
mating
success
female
preference
+
+
discussion
9
8
bite
force
Bite force (N)
7
+
5
+
females
trade off!
+
35
mating
success
female
3
2
+
fighting
ability
6
4
body
condition
males
+
preference
40
45
50
SVL (mm)
tail
length
+
55
60
65
discussion
bite
force
+
+
body
condition
tail
length
+
fighting
ability
+
mating
success
female
preference
+
+
discussion
bite
force
+
+
body
condition
tail
length
+
fighting
ability
+
mating
success
female
preference
+
+
discussion
bite
force
intrasexual competition
 determines dominance
 selection for higher bite forces
intersexual competition
 harms females during copulation
 low selection for bite force
 good genes
 selection for higher bite forces
sexual selection pressure = condition dependent!
Thanks to…
- Instituto Pirenaico de Ecología, Huesca
- Consejo superior de Investigaciones Científicas (Ramon y Cajal)
- FWO-Vl

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