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. 2012 Mar 21;279(1739):2855–2861. doi: 10.1098/rspb.2012.0181

Table 1.

Sources of variation in fertilization rates when sperm have direct access to eggs (no-choice experiment) and the direction of sperm movement and subsequent fertilization rates in dichotomous choice trials (egg-choice experiment) in the mussel, Mytilus galloprovincialis. For each model, sums of squares (SS) and degrees of freedom (d.f.) were computed individually for each block and summed to estimate the mean squares (MS) for each analysis. Significance levels for male and female effects were assessed by dividing their respective mean squares by the interaction mean squares [21]. Significant effects are presented in bold text. The d.f. associated with the error variance for each block was calculated from the formula NM NF (n − 1), where NM = 2, NF = 2, and n = number of replicate crosses = 2. As with d.f. associated with main effects, error d.f. were summed across blocks for the final analysis [21].

source of variation d.f. SS MS F p
(a) no-choice experiment: fertilization
male 15 0.091 0.006 1.076 0.445
female 15 3.548 0.237 41.94 <0.0001
interaction 15 0.085 0.006 1.945 0.036
error 60 0.174 0.003
(b) egg-choice experiment: sperm numbers
male 15 3 544 513 236 301 2.820 0.027
female 15 2 169 863 144 658 1.727 0.151
interaction 15 1 256 763  83 784 2.049 0.026
error 60 2 453 150  40 886
(c) egg-choice experiment: fertilization
male 13 1.560 0.120 4.065 0.008
female 13 1.062 0.082 2.767 0.039
interactiona 13 0.384 0.030 1.472 0.160
error 52 1.043 0.020

aThe interaction term for fertilization rates in the egg-choice experiment was marginally significant (p = 0.05) when data from one block with high residual error variance (on average 5.2 times higher than all other replicates) was removed from the analysis.