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Nature manuscript 2004-04-18179. Vieites et al. Post-mating clutch piracy
in an amphibian
Supplementary material
Supplementary material A. Temporal daily pattern of spawning over the entire
breeding period in 2001. Bars indicate the percent of clutches deposited at a
certain time. Hours of permanent observation are shaded with grey. No
nocturnal spawning occurred as verified by clutch counts at each morning.
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Supplementary material B. Statistical procedure to calculate the Imates
parameter.
Following Shuster and Wade (2003), the opportunity for sexual selection
(the Imates parameter) can be estimated from the opportunity of selection in
males and females in the population1. To test for the presence of sexual
selection in the population, we estimated the Imates parameter assuming a
conservative scenario and in absence of clutch piracy. The opportunity for
selection of females (Ifemales) can be calculated as the variance in fitness (as
offspring numbers) among females divided by the squared average in fitness
among all females. All females that approach a water body during the breeding
season do so for reproduction, and they spawn only one clutch per year. Our
count of clutches is therefore a precise estimate of the number of females
present in the population (119). Both, the variance and the average in progeny
numbers were calculated from 31 control clutches reared in the laboratory and
not exposed to clutch piracy, and these values were considered to be
representative for the whole female population.
Imales is the opportunity for selection of males and can be calculated by
using the same formula. However, in this case, the total number of males
estimated in the population by mark-recapture was higher than the number of
females (250 males), suggesting than in absence of clutch piracy more than the
half of the males would not be able to reproduce with a female. We
unambigously determined the paternal male for many clutches in the
population, but this information is not available for all clutches. Hence, we
cannot know the fraction of males that mated with more than one female, but
we can perform a conservative estimate in which we assume that each male
mated only once (again, clutch piracy is not considered in the calculation).
Under this assumption, out of 250 males in the population, 119 males would
have mated with a female, the remaining 131males would not have mated; their
fitness in terms of offspring would be zero. Hence, we assumed that the data
from the 31 tested clutches were representative for the fitness values of the
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portion of mated males (the 31 parentals of the 31 clutches make up 26% of the
total of 119 parentals in the populations). The whole variance and squared
mean for the males in the population can be calculated by including the same
proportion of males (26% out of 131 males that did not reproduce) from the nonmated category.
Imates can then be estimated using the following formula, proposed by
Shuster and Wade (2003):
Imales – Ifemales = (Ro - 1)*Ifemales + I mates
Being Ro the mean operational sex ratio (OSR).
References
1. Shuster, S. M. & Wade, M. J. Mating Systems and Strategies. Monographs in Behavior and
Ecology. (Princeton University Press, New Jersey, 2003).
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Supplementary material C. Microsatellite loci used for the paternity analysis,
primer sequences, number of alleles observed in the population, and number of
adult specimens genotyped. Observed and expected heterozygosities for the
adult population are also shown.
Heterozygosity
Locus
Primer sequence (5' - 3')
RtU4
GGCTTCAAAGTAGAATAAAG
No. of alleles
n
Obs.
Exp.
Reference
8
57
0.719
0.739
1
12
58
0.914
0.804
1
5
58
0.759
0.642
2
10
58
0.603
0.763
2
16
57
0.877
0.851
3
AATCTTTTCCTTACTGTA
RtU7
GCATTATTACAGCATTCTGGAT
TTAATGGCTTGGATAGATTTACC
Rtempµ4 TCATGCAGGCAATCA
AGAACCGCTGGTGTCCCAAC
Rtempµ6 TCTTCTTTACATATATATGGATG
CCTAGTTGGGGATTGGTCAG
Rtµb
AAAGACAGACGGATTCCCCATTCA
GGTTGTAGTGTCAAGTTTTCAGAG
References
1. Berlin, S., Merilä, J. & Ellegren, H. Isolation and characterization of polymorphic microsatellite
loci in the common frog, Rana temporaria. Mol. Ecol. Notes 9, 1919-1952 (2000).
2. Rowe, G. & Beebee, T. J. C. Polymerase chain reaction primers for microsatellite loci in the
common frog Rana temporaria. Mol. Ecol. Notes 1, 6-7 (2001).
3. Pidancier, N., Gauthier, P., Miquel, C. & Pompanon, F. Polymorphic microsatellite DNA loci
identified in the common frog (Rana temporaria, Amphibia, Ranidae). Mol. Ecol. Notes 2, 304–
305 (2002).
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Supplementary material D. Snout-vent lengths of parental males and females
in pairs of Rana temporaria in amplexus (data from 2001, 2002 and 2003).
Parental sizes were significantly correlated in 2001 (Spearman rank correlation,
rs = 0.61, P = 0.0032, n = 21) and over the whole three-year period (rs = 0.49, P
= 0.0004, n = 48) suggesting size-assortative mating. Symbols represent data
from year 2001 (squares), 2002 (triangles) and 2003 (circles).