S. Calhim, H. M. Lampe, T. Slagsvold & T. R. Birkhead
Selection on sperm morphology under relaxed sperm competition in a wild passerine bird
SUPPLEMENTARY MATERIAL
Table S1. Literature review of the evidence for a phenotypic association between sperm phenotype
(morphometry and function) and secondary sexually selected traits.
Sperm Trait
Species
Association with a secondary
sexually-selected trait
Reference
Anas platyrhynchos
Positive
Bill colouration
Peters et al. (2004)
Cervus elaphus
Positive
Antler size
Malo et al. (2005)
Coregonus fatioi
Mixed
Urbach et al. (2007)
Gallus gallus spp.
Mixed
Lepomis macrochirus
None
Body size, condition,
asymmetry
Ornament size; social
status
Body condition
Poecilia reticulata
Mixed
Rutilus rutilus
None
Locatello et al. (2006); Skinner &
Watt (2007); Pitcher et al. (2007)
Kortet et al. (2004)
Salvelinus alpinus
Positive
Body colouration; body
size
Ornamentation
elaboration
Body colouration
Taeniopygia guttata
None
Birkhead & Fletcher (1995)
Poecilia reticulata
Mixed
Song quality; plumage
traits
Body colouration
Rutilus rutilus
Positive
Ornamentation
elaboration
Acrocephalus schoenobaenus
None
Song quality traits
Birkhead et al. (1997)
Lepomis macrochirus
None
Body condition
Casselman & Montgomerie (2004)
Poecilia reticulata
Mixed
Taeniopygia guttata
None
Locatello et al. (2006); Skinner &
Watt (2007); Pitcher et al. (2007)
Birkhead & Fletcher (1995)
Poecilia reticulata
None
Body colouration; body
size
Song rate; breast plumage
symmetry
Body size; body
colouration
Sperm Function
Velocity or Motility
Viability or Longevity
Froman et al. (2002); Pizzari et al.
(2004); Parker et al. (2006)
Casselman & Montgomerie (2004)
Liljedal et al. (1999)
Locatello et al. (2006); Pitcher et
al. (2007)
Kortet et al. (2004)
Sperm Form
Size
Design
(i.e. midpiece)
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Skinner & Watt (2007); Pitcher et
al. (2007)
S. Calhim, H. M. Lampe, T. Slagsvold & T. R. Birkhead
Selection on sperm morphology under relaxed sperm competition in a wild passerine bird
SUPPLEMENTARY MATERIAL
Table S2. Within-male repeatability and sperm sampled per male.
Within-individual repeatability of sperm morphometric measurements (and 95% Cls) were calculated for three
sets of data, defined as the ratio between the number of males to number of sperm measured per individual.
These repeatability estimates reflect how much of the total variation in the data attributed to between male
differences. For a subsample of n= 9 males of the n=18 used in the current study, we had data for n= 30 sperm
per male used in a previous comparative study to assess intramale variation (Immler et al. 2008). Note that
intramale repeatability estimates from the dataset used in the current study (in bold) are comparable (for sperm
total length) or higher (for midpiece length) to those obtained from the larger number of sperm per male subsets.
Although larger numbers of sperm per individual are needed to accurately assess variation at the intramale level,
fewer sperm per individual can provide a reliable sample to distinguish between males when intermale
differences in mean trait sizes is also high (see Birkhead et al. 2005, Calhim et al. 2007, Immler et al. 2008).
Sperm Traits
N males
Total Length
18
5
0.63 (0.44, 0.81)
9
30
0.66 (0.46, 0.88)
9
5
0.58 (0.30, 0.86)
18
5
0.48 (0.27, 0.71)
9
30
0.26 (0.12, 0.58)
9
5
0.35 (0.08, 0.73)
Midpiece Length
N sperm per male Within-male repeatability (95% CLs)
Table S3. Full statistical output from Generalized Linear Models.
§ indicates model used in the manuscript.
log (Sperm Total Length) ~ Blackness + log (Breeding Date)
Term
estimate s.e.
intercept
4.951
0.144
Blackness
-0.0113 0.00496
Breeding Date (log)
-0.0969 0.0475
§ log (Sperm Total Length) ~ Blackness
Term
estimate
t
34.40
-2.29
-2.04
s.e.
p
< 0.0001
0.0452
0.0687
t value p
-2-
AIC
-57.35
AIC
Effect Size (95%CL)
S. Calhim, H. M. Lampe, T. Slagsvold & T. R. Birkhead
Selection on sperm morphology under relaxed sperm competition in a wild passerine bird
SUPPLEMENTARY MATERIAL
intercept
Blackness
4.663
-0.0158
0.0139
0.0038
335.31
-4.16
s.e.
0.161
0.051
t value p
31.30
< 0.0001
-2.74
0.0194
AIC
-53.88
log (Midpiee Length) ~ Blackness + log (Breeding Date)
Term
estimate s.e.
intercept
6.313
2.373
Sperm Total Length (log)
-0.344
0.477
Blackness
-0.0091 0.009
Breeding Date (log)
-0.085
0.085
t value
2.66
-0.72
-0.98
-0.99
p
0.026
0.489
0.352
0.348
AIC
-46.01
§ log (Midpiee Length) ~ log (Sperm Total Length) + Blackness
Term
estimate s.e.
intercept
5.021
1.520
Sperm Total Length (log)
-0.121
0.326
Blackness
-0.0095 0.0071
t value
3.30
-0.37
-1.34
p
0.005
0.716
0.201
AIC
-67.70
§ log (Midpiee Length) ~ log (Sperm Total Length) + log (Breeding Date)
Term
estimate s.e.
t value
intercept
5.001
1.961
2.55
Sperm Total Length (log)
-0.069
0.386
-0.18
Breeding Date (log)
-0.081
0.085
-0.95
p
0.028
0.861
0.366
AIC
-46.70
§ log (Sperm Total Length) ~ log (Breeding Date)
Term
estimate
intercept
5.051
Breeding Date (log)
-0.140
-3-
< 0.0001 -76.45
0.000836
-0.73 (-1.50, -0.36)
Effect Size (95%CL)
-0.63 (-1.43, -0.07)
Effect Size (95%CL)
-0.34 (-0.91, 0.21)
Effect Size (95%CL)
-0.28 (-0.98, 0.39)
S. Calhim, H. M. Lampe, T. Slagsvold & T. R. Birkhead
Selection on sperm morphology under relaxed sperm competition in a wild passerine bird
SUPPLEMENTARY MATERIAL
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