Animal Behaviour 78 (2009) 1357–1363
Contents lists available at ScienceDirect
Animal Behaviour
journal homepage: www.elsevier.com/locate/anbehav
Sexual selection for genetic quality: disentangling the roles of male
and female behaviour
Nina Pekkala*, Mikael Puurtinen, Janne S. Kotiaho
Centre of Excellence in Evolutionary Research, Department of Biological and Environmental Science, University of Jyväskylä
a r t i c l e i n f o
Article history:
Received 7 May 2009
Initial acceptance 9 July 2009
Final acceptance 24 August 2009
Available online 15 October 2009
MS. number: 09-00298
Keywords:
condition dependence
deleterious mutation
Drosophila montana
good genes
ionizing radiation
According to the good genes model of sexual selection, females choose males of good heritable genetic
quality to obtain offspring with high fitness. However, better mating success of high-quality males can
also be brought about by direct interference competition between males, or simply through elevated
activity of high-quality males. We examined the roles of different processes leading to sexual selection
for genetic quality in Drosophila montana. We manipulated genetic quality of male flies by inducing
mutations with ionizing radiation. We then recorded the effects of inherited heterozygous mutations on
several aspects of mating behaviour of males and females in two experiments. We found that mutations
reduced the probability of courtship and extended the latency to courtship of the males, suggesting male
activity plays a role in selection for genetic quality. However, the effects of mutations on mating success
and mating behaviour of the flies were in general weak. No evidence for female mate choice or interference competition between males acting against heritable mutations was found.
Ó 2009 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.
Sexual selection through mate choice, and in particular mate
choice for indirect fitness benefits, is a major paradigm that today
seems to enjoy almost unequivocal acceptance. A large body of
theoretical work has been built to explain the evolution of mate
choice in the absence of direct benefits (Andersson 1994; Andersson & Simmons 2006; Kokko et al. 2006), most of which critically
depends on a few assumptions: male sexual signals are costly, and,
because they are costly, they develop positive condition dependence (Andersson 1982, 1986; Rowe & Houle 1996; Kotiaho 2000,
2001; Hunt et al. 2004; Tomkins et al. 2004). Male condition
depends on many underlying physiological and morphological
traits and thus sums genetic variation over many loci (Rowe &
Houle 1996; Kotiaho et al. 2001; Tomkins et al. 2004). This multitude of loci provides a large target for deleterious mutations. By
choosing males with elaborate condition-dependent sexual signals,
females can thus avoid males with deleterious mutations and have
offspring with good genetic quality and high fitness.
These so-called good genes models and related research
emphasize the role of female mate choice in sexual selection for
* Correspondence: N. Pekkala, Centre of Excellence in Evolutionary Research,
Department of Biological and Environmental Science, P.O. Box 35, FIN-40014
University of Jyväskylä, Finland.
E-mail address: nina.a.pekkala@jyu.fi (N. Pekkala).
genetic quality of the male. However, as Whitlock & Agrawal (2009)
pointed out, genetic quality can affect mating success by its effects
on general activity and vigour of the male. Besides female choice,
competition among males for matings can come in many forms,
some involving direct communication or contact between males
(interference competition) and others only indirect competition,
for example via differences in the activity of males (Huntingford &
Turner 1987; Andersson 1994). If the outcome of the mating
competition among males depends on the condition of the male
(Ligon et al. 1990; Kotiaho et al. 1999), and condition is determined
by genetic quality, the winner of the competition should be of high
genetic quality. Thus, competition among males, whether direct or
indirect, can lead to the same outcome as female mate choice:
apparent benefits in terms of good genes to the offspring. Clearly,
the process of sexual selection can operate in many different ways,
and special experimental designs are needed to unravel the
mechanisms generating mating biases (see e.g. Wong & Candolin
2005; Kotiaho & Puurtinen 2007; Fitze et al. 2008).
Theoretical models suggest that sexual selection could reduce
mutational load from populations, but only a few empirical studies
have evaluated the effectiveness of sexual selection against deleterious mutations and none of these studies have detailed the
process of sexual selection for genetic quality (reviewed in Whitlock & Agrawal 2009). Our aim was to study experimentally the
effectiveness of sexual selection against deleterious mutations, as
0003-3472/$38.00 Ó 2009 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.
doi:10.1016/j.anbehav.2009.09.003
N. Pekkala et al. / Animal Behaviour 78 (2009) 1357–1363
well as to disentangle the relative importance of female mate
choice, interference among males, and male activity for sexual
selection for genetic quality. We manipulated genetic quality of
Drosophila montana by exposing the fathers of the experimental
males to ionizing radiation known to produce a wide range of
mutations in DNA (reviewed in Evans & DeMarini 1999). To mimic
the situation in natural populations where novel mutations are
likely to occur mainly as heterozygotes, we studied the effects of
mutations from males heterozygous for the new heritable
mutations.
METHODS
Study Species
Drosophila montana is a boreal species belonging to the D. virilis
group of Drosophila flies. In nature, D. montana flies gather on food
patches to court and mate (Aspi et al. 1993). Courting consists of the
male chasing the female, touching the female with its legs, head
and mouthparts, and producing a courtship song by vibrating its
wing (Hoikkala & Lumme 1987; Liimatainen et al. 1992; personal
observation). Courtship song is a species-specific signal that
females require before allowing the male to mate (Liimatainen et al.
1992). Both female choice and male–male competition are made
possible at the gatherings of the flies, and the species has become
a model species for sexual selection studies (Hoikkala & Aspi 1993;
Aspi & Hoikkala 1995; Hoikkala et al. 1998; Ritchie et al. 1998;
Hoikkala & Suvanto 1999; Klappert et al. 2007).
Maintenance and Manipulation of Flies
The flies for the study came from a laboratory stock originating
from Kawasaki, Japan. The stock had been inbred for 20 generations
with full sib mating to create a (nearly) homozygous line, and then
reared in bottles containing malt medium in constant light at
19 1 C. For the experiments, the flies were sexed under CO2
anaesthesia 1–4 days after their emergence and maintained in
single-sex groups in plastic vials (diameter 23.5 mm, height
75.0 mm) containing malt medium.
We manipulated genetic quality of randomly selected 4–7-dayold male flies by inducing new mutations with ionizing gamma
radiation. An inbred line was used to minimize the initial variation
in genetic quality so that the effects of induced mutations would be
easier to detect. Nine doses of radiation were used: 0, 5, 10, 15, 20,
25, 30, 35 and 40 Grays (Gy). The number of mutations induced is
expected to increase with increasing dose of radiation (Edington
1957; reviewed in Evans & DeMarini 1999). For the 0 Gy level
(control) the flies were treated otherwise the same but were not
given any radiation. The maximum amount of radiation was set to
40 Gy because of the substantial decrease in fertility of the males at
high doses of radiation (Fig. 1). We treated 40–50 males for each
radiation dose.
Once the irradiated males were sexually mature (14–17 days
old) they were each mated to a nonirradiated stock female. Male
offspring of these matings, heterozygous for the new heritable
mutations, were used in the experiments. These males are called
experimental males from here on. For the last 7 days before the
experiments, the experimental males were each reared individually
in a plastic vial containing malt medium.
For mating experiment 2 (see Experimental set-up), male flies
from the laboratory stock were anaesthetized with CO2 1 week
before the experiments and marked for identification by cutting off
a small piece from the tip of their wing. After that they were reared
in plastic vials containing malt medium in groups of four until the
experiments.
35
Number of offspring (95% CI)
1358
30
25
20
15
10
0
5
10
15
20
25
30
Radiation dose (Gy)
35
40
Figure 1. Relationship between radiation dose and fertility of the irradiated males.
Symbols represent mean number of offspring and error bars the 95% confidence
interval. Offspring were counted from tubes where a stock female and an irradiated
male (or a control male in the case of 0 Gy) were allowed to mate and lay eggs for 4
days (linear regression: F1,435 ¼ 54.433, P < 0.001).
All flies used in the experiments were virgin. The flies were 20–
29 days old during the experiments, the age distribution between
the radiation treatments and the two mating experiments being
the same.
Experimental Set-up
We aimed to determine the roles of different processes of sexual
selection for genetic quality by examining the effects of inherited
heterozygous mutations of the experimental males on several
aspects of mating behaviour of the flies. We conducted two mating
experiments. In mating experiment 1 (ME1), an experimental male
was introduced to a stock female. In mating experiment 2 (ME2), an
experimental male and a stock male were simultaneously introduced to a stock female. In ME1, effects of inherited mutations on
mating behaviour of the flies are thus an outcome of female choice
and/or activity of the male, whereas in ME2 there is also a possibility for interference among males and an opportunity for the
female to compare the two males and thus choose between them.
By comparing the effects of inherited mutations on different
aspects of mating behaviour in the two experiments we can evaluate the relative importance of female choice, interference among
males, and male activity on sexual selection for genetic quality.
In both mating experiments we recorded the following aspects
of behaviour of the experimental male or the female.
(1) Male courtship (yes/no). Male courtship was recorded as
a discrete variable: male courted or did not court the female. Any
form of male courtship behaviour (chasing, touching or producing
a courtship song) was recognized as courtship. In ME1, male
courtship was considered to indicate activity of the male. In ME2,
male courtship could also be influenced by interference among
males. We expected mutations to reduce courtship of the males.
(2) Latency to courtship (s). Latency to courtship is a measure of
how long it takes the male to start courtship (i.e. time between
beginning of the experiment and beginning of courtship). In ME1,
latency to courtship was considered to indicate activity of the male. In
ME2, latency to courtship could be further influenced by interference
among males. We expected mutations to extend latency to courtship.
(3) Amount of courtship required by female (s). Courtship of
D. montana males typically consists of periods of courting and periods
of not courting. In D. montana, forced copulations are extremely rare.
Summing the periods of active courtship before mating thus gives the
amount of active courtship required by the female before mating. The
N. Pekkala et al. / Animal Behaviour 78 (2009) 1357–1363
amount of courtship required by the female was considered to be
influenced by female choice. We expected females to require longer
courtship from males with more mutations.
(4) Mating success (yes/no). Mating success was recorded as
a discrete variable: the male mated or did not mate. In ME1, mating
success could be influenced by female choice and activity of the
male. In ME2, interference among males and relative female mate
choice could have an additional effect. We expected mutations to
reduce mating success of the males.
(5) Latency to mating (s). Latency to mating measures how long
it takes the male to mate with the female (i.e. time between
beginning of the experiment and beginning of copulation). In ME1,
latency to mating could be influenced by male activity and female
choice. In ME2, interference among males and relative female mate
choice could also play a role. We expected mutations to extend
latency to mating.
(6) Duration of mating (s). If females mate with several males,
extended copulation may be beneficial to the male because of
different aspects of sperm competition (Simmons 2001). Multiple
mating with several males is common among D. montana females,
although why this occurs is not known (Aspi 1992; Aspi & Lankinen
1992; see also Arnqvist & Nilsson 2000). Drosophila montana
females terminate the copulation by vigorously kicking with their
hindlegs to dislodge the male. The males try to resist this behaviour,
and prefer longer copula durations than females (Mazzi et al. 2009).
Duration of mating could thus depend on both female choice and
persistence (activity) of the male. We expected mutations to
shorten mating duration of the males.
(7) Order of courtship (first/second). Order of courtship was
recorded as a discrete variable (in ME2 only): the experimental
male started to court first or second. If only one of the males
courted the female, the courting male was considered to be the first
to court and the noncourting one to be the second. Order of
courtship could be affected by the activity of the male and interference among the males. We expected mutations to reduce the
probability of being the first to court.
The experiments were conducted in petri dishes (diameter
5.0 cm, height 0.7 cm) covered with nylon net. The floor of the dish
was covered with a moistened filter paper to create optimal
conditions for the flies. The paper was allowed to dry before use in
a new trial. First the male (in ME1) or males (in ME2) and then the
female were placed into the petri dish. Timing began from introduction of the female. We observed the behaviour of the flies until
copulation occurred, or until 30 min had elapsed. Both mating
experiments were performed each day in randomized order for 25
days, ME1 twice a day and ME2 four times a day. For each experiment, all treatments of radiation were observed simultaneously.
Thus, the environmental conditions (temperature, time of day, air
moisture, etc.) did not differ between the radiation treatments. In
ME1, all nine doses of radiation were included. In ME2, because of
the more demanding simultaneous observation of two males, only
doses of 0, 5, 10, 20, 30 and 40 Gy were included.
Statistical Analyses
For all statistical analyses we used SPSS 12.0.1 (SPSS Inc., Chicago, IL, U.S.A.). All the P values are from two-tailed tests. The
discrete variables were tested with logistic regression. Thus,
courtship and mating success of the experimental males were
tested as the regression of the proportion of males that courted or
mated the female, respectively, on the radiation dose of the
parental males. The relationship between radiation dose and order
of courtship was tested similarly in ME2.
The latency measures, amount of courtship required by the female
and duration of mating were tested with Jonckheere–Terpstra
1359
analysis. This is a powerful nonparametric test developed for
situations where the groups to be compared have a natural order
(here radiation doses of the fathers of the experimental males;
Sheskin 2004). The trials in which courtship or mating did not happen
within the 30 min observation were excluded from the analysis of the
respective latency measures. The correlation between latency to
courtship and latency to mating was analysed with Spearman
nonparametric correlation.
Estimates for effect size (r) of mutations on all variables were
calculated from the test statistics and sample sizes following
Rosenthal (1991).
RESULTS
In ME1 with one experimental male, 95.0% of the males courted
the female and 85.1% of these mated. Mutations reduced the
probability of courtship of the males (Table 1, Fig. 2). In addition,
mutations extended the latency to courtship of the males that did
court (Table 1, Fig. 3). Total time to mating was longer for males that
started their courtship later, as latency to courtship and latency to
mating correlated positively (rS ¼ 0.273, N ¼ 337, P < 0.001).
Mutations had no statistically significant effects on the other variables measured (Table 1).
In ME2 with one experimental male and one stock male, 85.2%
of the experimental males courted the female and 69.1% of these
mated. In 59.4% of the trials one of the males and in 38.8% of the
trials both males courted the female. None of the measured variables was significantly affected by mutations of the experimental
males (Table 2). As in ME1, latency to courtship and latency to
mating were positively correlated (rS ¼ 0.445, N ¼ 326, P < 0.001).
In the vast majority of the ME2 trials, the males had some
physical contact with each other (wing vibration and touching). In
some cases the males tried to court simultaneously and interrupt
each other’s courtship. When we compared the probability of
courtship and the latency to courtship of the experimental males in
the control (0 Gy) treatment between ME1 and ME2, it was clear
that there was interference competition among males in ME2. The
presence of the competing stock male reduced the courtship
probability (Pearson c21 ¼ 7.822, P ¼ 0.005) and increased the
courtship latency of the experimental males (Mann–Whitney U
test: U ¼ 1210.5, N1 ¼ 48, N2 ¼ 83, P < 0.001). However, interference among males did not make sexual selection against deleterious mutations stronger, as no significant effects of mutations
were detected on any of the recorded variables, and the effect size
estimates were not inflated compared to ME1 (Tables 1, 2).
In both mating experiments, statistically nonsignificant effects
were not due to low power of tests, as even very weak effects of
radiation (r > 0.11) would be significant at the a ¼ 0.05 level, given
the amount of data in the study (see Tables 1, 2). See the Appendix
for descriptive statistics for all the variables measured in ME1 and
ME2.
Table 1
Effect of induced mutations on variables recorded in mating experiment 1
Variable
N
Test statistic
df
P
r
Male courtship
Latency to courtship
Amount of courtship required
by female
Mating success (all males)
Mating success (males that courted)
Latency to mating
Duration of mating
424
401
334
c2¼7.644
1
–
–
0.006
0.035
0.763
0.134
0.105
0.017
1
1
–
–
0.137
0.868
0.275
0.808
0.073
0.008
0.059
0.014
417
396
339
309
J–T¼2.105
J–T¼0.302
c2¼2.211
c2¼0.028
J–T¼1.092
J–T¼0.243
N denotes the number of mating trials and r is the effect size estimate, calculated
from the test statistic (J–T is the standardized Jonckheere–Terpstra statistic).
Significant results are indicated in bold.
Proportion of males that performed
courtship (95% CI)
1360
N. Pekkala et al. / Animal Behaviour 78 (2009) 1357–1363
Table 2
Effect of induced mutations on variables recorded in mating experiment 2
1
0.9
0.8
0.7
Variable
N
Test statistic
df
P
r
Male courtship
Latency to courtship
Amount of courtship required
by female
Mating success (all males)
Mating success (males that courted)
Latency to mating
Duration of mating
Order of courtship
562
477
325
c2¼1.829
1
–
–
0.176
0.941
0.888
0.057
0.004
0.008
1
1
–
–
1
0.947
0.478
0.635
0.357
0.086
0.003
0.032
0.026
0.054
0.077
561
478
329
288
553
J–T¼0.074
J–T¼0.141
c2¼0.004
c2¼0.503
J–T¼0.475
J–T¼0.922
c2¼3.295
N denotes the number of mating trials and r is the effect size estimate, calculated
from the test statistic (J–T is the standardized Jonckheere–Terpstra statistic).
0.6
0
5
10
15
20
25
30
35
40
Radiation dose (Gy)
Figure 2. Proportion of experimental males that courted the female in mating
experiment 1 as a function of radiation dose of the parental males (confidence intervals are calculated following Zar 1999).
DISCUSSION
Overall, we found inherited heterozygous mutations of
D. montana males to have relatively weak effects on mating
behaviour of the flies. Most strikingly, mating success of the males
was not affected by mutations in either of the mating experiments.
However, in the experiment with only one male (ME1), we found
mutations reduced the probability of courtship of the males. In
addition, in the cases where males did court, the more mutated
males started their courtship later. These results suggest a role for
male activity in sexual selection for genetic quality in D. montana. In
nature, lower probability of courtship would inevitably lead to
lower mating success of the males: if you don’t court you don’t get
to mate. Also, latency to courtship could be crucial for mating
success of the males. In laboratory experiments, D. montana
females often accept the male that courts first (here in 76% of the
cases in the mating experiment with two males). If the same is true
in nature, beginning the courtship before other males will result in
a major benefit in competition over mates. Furthermore, longer
latency to mating is likely to decrease the overall mating success of
the males, that is, reduce the number of matings the male gets in
his entire lifetime (Shackleton et al. 2005; see also McGhee et al.
2007). In our study, mutations did not affect mating latency of the
males directly, but latency to courtship did correlate positively with
latency to mating. Other, indirect evidence for the effect of genetic
quality on male activity in D. montana can be found from the study
Latency to courtship (median, s)
50
45
40
35
30
25
20
0
5
10
15
20
25
30
Radiation dose (Gy)
35
40
Figure 3. Latency to courtship (median,s) of the experimental males in mating
experiment 1 as a function of radiation dose of the parental males.
of Hoikkala & Suvanto (1999), where they reported D. montana
males performing high-frequency courtship song to be more active
in their courtship behaviour. Courtship song frequency has been
suggested to indicate genetic quality in D. montana (Hoikkala et al.
1998).
In contrast to the experiment with one male (ME1), in the
mating experiment with two males (ME2), no significant effects of
mutations on courtship behaviour of the males were detected.
Observations of contact between the males in most of the mating
trials and reduced courting of the experimental males in the
presence of the other male indicate interference between the
males. However, no evidence for selection against mutations via
interference competition was found. Rather than amplifying the
effects of mutations seen in ME1, the presence of the other male
seemed to mask these effects in ME2. Most likely the small effects
of mutations detected in ME1 were concealed by the strong effects
of the competing male on courtship probability and courtship
latency of the males in ME2. It is difficult to relate these findings to
natural settings where the effects of male activity may be greatly
intensified compared to the confined space of a petri dish, but
interference between males may also be frequent.
Previous studies have suggested that D. montana females prefer
genetically superior males, based on evidence of relationships
between courtship song frequency and genetic quality of the males
(Hoikkala et al. 1998) and between courtship song frequency and
female preference (Ritchie et al. 1998; Hoikkala & Suvanto 1999; but
see Klappert et al. 2007). However, we found no evidence for female
mate choice against males with more mutations. In ME1, this might
be an artefact of the experimental design, females accepting any
male when they did not have better males to choose from (Hoikkala
& Aspi 1993). However, in ME2, females did have two males to
choose from, but still no significant effect of mutations on the mating
success of the males, amount of courtship required by the female,
latency to mating or duration of mating was detected.
Only a few empirical studies have examined the role of sexual
selection in removing deleterious mutations, despite theoretical
models suggesting that this may affect the reproductive output of
individuals and thus the viability of populations, and even the
maintenance of sexual reproduction (reviewed in Whitlock &
Agrawal 2009). Whitlock & Bourguet (2000) as well as Sharp &
Agrawal (2008) documented how mutations that reduce female
fecundity and egg-to-adult survivorship may also reduce male
mating success in Drosophila melanogaster. MacLellan et al. (in
press) showed, again in D. melanogaster, that deleterious mutations
may harm males’ ability to find mates. However, all of these studies
used single or a few mutations with clearly visible phenotypic
effects, either homozygous recessives (Whitlock & Bourguet 2000;
MacLellan et al., in press) or heterozygous mutations with phenotypically dominant effects (Sharp & Agrawal 2008). In nature,
mutations can, however, occur in many different loci and have any
N. Pekkala et al. / Animal Behaviour 78 (2009) 1357–1363
degree of dominance. In a more realistic setting with bulb mites,
Rhizoglyphus robini, Radwan (2004) found that sexual selection
eliminated randomly induced heterozygous mutations from populations, but he did not identify the process by which less mutated
males were favoured. We found that random mutations decreased
the courting probability and increased the latency to courtship in D.
montana males. To influence population fitness, sexual selection
would have to remove mutations that reduce the reproductive
output of the population. With the current data set we are unable to
determine whether the induced mutations only affected male
mating behaviour, or if they also affected other fitness traits.
However, given the presumed multitude of loci affecting condition
(Rowe & Houle 1996; Kotiaho et al. 2001; Tomkins et al. 2004), it
would be surprising if randomly induced mutations only influenced
courtship behaviour of the males.
The good genes models of sexual selection and the great amount
of related research emphasize the role of females choosing goodquality males to mate with (Zahavi 1975, 1977; Pomiankowski
1988; Maynard Smith 1991; Andersson 1994; Kokko et al. 2006).
However, it is often forgotten that the mechanisms generating
mating bias cannot be inferred from possible indirect fitness
benefits from mating with genetically superior males; if genetic
quality and male competitiveness or male activity are correlated,
genetically superior males will be more successful even without
active female choice (Kokko et al. 2003; Kotiaho & Puurtinen 2007).
We found no evidence for active female mate choice for genetically
superior males; nor did we find evidence for direct male–male
competition acting against inherited mutations of the males.
Instead, the results suggest that sexual selection for genetic quality
may operate simply via the effects of male activity.
Acknowledgments
We thank Professor Anneli Hoikkala for practical advice with the
mating experiments. We also thank the staff of the Radiology
Hospital of Central Finland Health Care District in Jyväskylä, who
kindly gave their equipment and expertise for our use, in particular
physicist Pekka Sjöholm. The study was funded by Academy of
Finland’s Centre of Excellence in Evolutionary Research.
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APPENDIX
Table A1
Number of mating trials (N total) and number and proportion of males that courted and mated in ME1
Radiation dose (Gy)
0
5
10
15
20
25
30
35
40
Total
N total
% Mated (from total)
% Mated (from courted)
50
49
49
49
46
49
47
48
37
N courted
49
48
49
46
45
45
44
44
33
% Courted
98.0
98.0
100.0
93.9
97.8
91.8
93.6
91.7
89.2
N mated
43
38
42
37
40
40
41
36
26
86.0
77.6
85.7
75.5
87.0
81.6
87.2
75.0
70.3
89.8
79.2
85.7
82.6
88.9
91.1
93.2
81.8
78.8
424
403
95.0
343
80.9
85.1
Radiation dose expresses the radiation dose of the fathers of the experimental males.
Table A2
Latency to courtship and mating in ME1
Radiation dose (Gy)
Latency to courtship (s)
N
0
5
10
15
20
25
30
35
40
Total
Latency to mating (s)
Mean
SE
Median
Mean
SE
Median
48
48
49
46
45
45
44
44
32
93.3
131.0
152.7
76.7
108.8
205.0
103.5
147.3
80.7
32.3
39.0
41.7
23.5
20.3
46.0
18.6
46.7
15.8
33.0
35.5
36.0
28.0
49.0
45.0
41.5
47.5
42.0
N
42
36
42
37
40
40
41
35
26
482.9
308.0
329.5
385.7
421.0
431.9
491.0
309.2
471.7
79.0
44.5
45.5
53.8
57.8
62.2
68.8
50.0
79.2
237.5
204.5
230.5
296.0
305.0
305.5
343.0
234.0
425.0
401
123.5
11.6
37.0
339
403.6
20.5
281.0
N denotes number of mating trials. Radiation dose expresses the radiation dose of the fathers of the experimental males.
Table A3
Amount of courtship reqiured by female and duration of mating in ME1
Radiation dose (Gy)
Amount of courtship required by female (s)
N
0
5
10
15
20
25
30
35
40
Total
Duration of mating (s)
Mean
SE
Median
Mean
SE
Median
41
35
42
37
39
40
39
36
25
212.3
99.6
170.3
199.1
211.8
174.1
199.4
150.9
180.6
34.5
15.5
27.3
30.6
43.0
29.8
33.6
28.1
30.7
133.0
64.0
116.0
144.0
85.0
84.0
147.0
80.5
135.0
N
40
31
40
35
38
34
37
29
25
243.7
251.6
235.8
246.5
241.1
267.3
240.7
239.5
255.7
8.7
11.5
8.0
8.2
8.3
13.9
9.6
8.9
12.0
236.5
251.0
235.0
238.0
231.5
248.5
236.0
237.0
245.0
334
178.6
10.6
101.0
309
246.3
3.3
238.0
N denotes number of mating trials. Radiation dose expresses the radiation dose of the fathers of the experimental males.
Table A4
Number of mating trials (N total) and number and proportion of experimental males that courted and mated in ME2
Radiation dose (Gy)
0
5
10
20
30
40
Total
N total
% Mated (from total)
% Mated (from courted)
98
97
97
99
91
80
N courted
83
85
85
87
75
64
84.7
87.6
87.6
87.9
82.4
80.0
% Courted
54
55
65
59
51
47
55.1
56.7
67.0
59.6
56.0
58.8
65.1
64.7
76.5
67.8
68.0
73.4
562
479
85.2
331
58.9
69.1
Radiation dose expresses the radiation dose of the fathers of the experimental males.
N mated
N. Pekkala et al. / Animal Behaviour 78 (2009) 1357–1363
1363
Table A5
Latency to courtship and mating for experimental males in ME2
Radiation dose (Gy)
Latency to courtship (s)
N
0
5
10
20
30
40
Total
Latency to mating (s)
Mean
SE
Median
Mean
SE
Median
83
84
84
86
75
65
172.2
164.9
132.4
171.0
159.9
160.3
32.6
26.5
23.6
27.8
29.0
25.1
70.0
74.5
51.5
70.5
54.0
81.0
N
54
54
65
59
51
46
387.4
453.4
355.1
403.2
367.5
466.9
51.5
60.1
47.3
58.3
47.2
65.4
221.5
268.5
193.0
251.0
214.0
329.5
477
160.1
11.3
69.0
329
402.7
22.4
249.0
N denotes the number of mating trials. Radiation dose expresses the radiation dose of the fathers of the experimental males.
Table A6
Amount of courtship required by female and duration of mating in ME2
Radiation dose (Gy)
0
5
10
20
30
40
Total
Total amount of courtship required by
female (s)
Amount of courtship required by female
(s)
Duration of mating (s)
N
N
N
Mean
SE
Median
Mean
SE
Median
Mean
SE
Median
71
70
79
75
65
55
141.8
169.2
114.8
148.7
155.3
163.6
20.6
21.2
14.1
24.4
19.7
27.5
63.0
102.5
61.0
76.0
95.0
76.0
54
54
64
57
51
45
117.4
127.0
100.1
119.8
112.7
132.7
23.9
22.6
14.7
23.2
17.4
27.8
47.0
64.5
46.5
59.0
75.0
48.0
51
44
60
48
45
40
248.1
254.1
255.6
239.5
228.8
259.3
7.7
12.3
6.2
10.6
6.4
11.3
248.0
236.0
250.5
238.0
230.0
241.0
325
147.5
8.6
82.0
325
117.4
8.7
57.0
288
247.6
3.7
240.5
Total amount of courtship is the amount of courtship of the two males (experimental male and stock male) together. Amount of courtship required by female and duration of
mating are expressed for experimental males. N denotes the number of mating trials. Radiation dose expresses the radiation dose of the fathers of the experimental males.