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+1

+2

+3

Mean

0.488 ± 0.066

1.064 ± 0.037

0.982 ± 0.049

0.917 ± 0.224

0.527 ± 0.145

1.046 ± 0.043

0.919 ± 0.051

0.798 ± 0.222

1.008 ± 0.056

0.919 ± 0.065

1.047 ± 0.041

0.947 ± 0.182

0.941 ± 0.039

0.947 ± 0.037

0.952 ± 0.026

0.870 ± 0.138

1.113 ± 0.040

1.136 ± 0.044

1.082 ± 0.073

1.115 ± 0.028

1.077 ± 0.067

1.114 ± 0.052

1.204 ± 0.109

1.048 ± 0.107

1.104 ± 0.039

1.079 ± 0.059

1.114 ± 0.067

1.083 ± 0.024

1.003 ± 0.237

0.984 ± 0.077

0.942 ± 0.083

0.970 ± 0.038

+1

+2

+3

0.039

−0.018

−0.063

P = 0.271

P = 0.214

P = 0.023

−0.068

0.028

−0.094

P = 0.014

P = 0.182

P < 0.001

−0.036

−0.021

0.122

P = 0.133

P = 0.221

P = 0.019

−0.101

−0.095

−0.172

P = 0.152

P = 0.016

P = 0.001

Therefore, although the trade-off pattern is general, it cannot be universal. Which is more important in considering and discussing evolutionary trade-offs? Is the glass two-thirds full, one-third empty, or partly inverted? The prediction must be that trade-offs will generally occur, but they may fail to happen in some or even many individual instances, and correlated responses may sometimes even be opposite in sign to those expected under the trade-off hypothesis.

Quantitative Relationship Between Direct and Correlated Responses

The previous section dealt with the qualitative aspects of the trade-off hypothesis, as indicated by the sign of the correlated response. Levins’ (1968) principle of allocation also predicts a quantitative association between the magnitude of adaptation to one environment and its trade-off



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