FIGURE 4 Average values for eight environmental variables over 17 windows that follow the Bufo bufo – B in Environmental correlates of the European common toad hybrid zone

FIGURE 4 Average values for eight environmental variables over 17 windows that follow the Bufo bufo – B. spinosus hybrid zone from the Atlantic coast (window 1) to the Mediterranean (window 17). Variables shown are those selected by a logistic regression analysis, with 'species' as dependent variable and explanatory variables available for selection as in table 1. Units are as in table 1; see also Hijmans et al. (2005). Values for B. bufo and B. spinosus are shown by small and large dots, respectively. Grey areas indicate that values for B. bufo are lower than for B. spinosus. The graph at the top left provides AUC model fit values along with major topographical references. Rectangles indicate stretches of the species contact for which the environmental models have good fit (AUC> 0.8), with consistent results indicated by green shadings. For the other windows with less than good model fit, signals are likely to be absent or void, either from poor sampling (window 1), the presence of rivers (windows 5–9, 13–14), or a thin or absent species' contact (windows 16–17) (see fig. 3).