Skip to main content
. 2016 Jun 12;6(14):4711–4730. doi: 10.1002/ece3.2243

Table 1.

The linear and nonlinear effects of daily protein (P) and carbohydrate (C) intake on (A) male sex pheromone expression (3H2B, 2MT, 4E2M) and (B) female clutch size and gestation time

Trait Linear effects Nonlinear effects
P C P × P C × C P × C
(A) Males
 3H2B
 Coefficienta ± SE −0.243 ± 0.054 0.539 ± 0.054 0.024 ± 0.049 −0.172 ± 0.027 −0.131 ± 0.104
 t 239 4.546 10.068 0.482 6.279 1.265
 P 0.0001 0.0001 0.630 0.0001 0.207
 2MT
 Coefficient ± SE −0.227 ± 0.053 0.557 ± 0.053 0.030 ± 0.049 −0.170 ± 0.027 −0.188 ± 0.102
 t 239 4.278 10.484 0.608 6.289 1.834
 P 0.0001 0.0001 0.544 0.0001 0.068
 4E2M
 Coefficient ± SE −0.131 ± 0.061 0.495 ± 0.061 0.011 ± 0.058 −0.149 ± 0.032 −0.254 ± 0.121
 t 239 2.163 8.161 0.197 4.670 2.097
 P 0.032 0.0001 0.844 0.0001 0.037
(B) Females
 Clutch size
 Coefficient ± SE 0.105 ± 0.070 0.351 ± 0.070 −0.079 ± 0.073 −0.142 ± 0.044 −0.356 ± 0.113
 t 226 1.489 5.004 1.082 3.263 3.151
 P 0.138 0.0001 0.280 0.001 0.002
 Gestation timeb
 Coefficient ± SE 0.022 ± 0.072 0.227 ± 0.072 0.034 ± 0.078 −0.039 ± 0.046 0.067 ± 0.120
 t 226 0.308 3.144 0.436 0.842 0.560
 P 0.759 0.002 0.663 0.401 0.576
a

The linear regression coefficients (i.e., P and C) describe the linear slope (given by β i) of the relationship between nutrient intake and the response variable, whereas the quadratic regression coefficients (i.e., P × P and C × C) describes the curvature (given by γ ii) of this relationship, with a negative γ ii indicating a convex relationship (i.e., a peak on the response surface) and a positive γ ii indicating a concave relationship (i.e., a trough on the response surface). The correlational regression coefficient (i.e., P × C) describes how the covariance between the two nutrients (γ ij) influences the response variable, with a negative γ ij indicating that a negative covariance between nutrients increases the response variable and a positive γ ij indicating that a positive covariance between nutrients increases the response variable. Full details of this approach are provided in Lande and Arnold (1983).

b

The sign of standardized gestation time was reversed for analysis to make this response variable directly comparable to other traits (i.e., a short gestation time is good for reproductive potential).