Table 2

Linear versus nonlinear models for the accumulation of hybrid incompatibility and other QTL between Solanum species. SSS, self seed set (seed sterility); PF, pollen fertility (arcsine square-root transformed); FSH, fruit shape; SSZ, fertile seed size. Model comparison 1: linear and quad1 (y = a1x + a2x2) models were compared using Zar Eq. 21.4 (23). Where P < 0.05, the more complex (quadratic) model provides a significantly better fit. Model comparison 2: linear and quad2 (y = ax2) models were compared by using AIC (24); the model that minimizes the AIC is considered the better fit [see (15)]. For results from least-squares regressions for each model (linear, quad1, and quad2) see table S4.

TraitModel comparison 1:
y = a1x vs. y = a1x + a2x2
Model comparison 2:
y = a1x vs. y = a1x2
FP valueAIC (linear)AIC (exp.)
Isolation QTL
SSS345.030.0342*6.27095.5647*
PF13.990.16634.849211.0081
Morphological QTL
FS2.290.37174.74317.4321
SSZ1.940.39645.29567.0262

*Results indicating better fit for nonlinear model.