Macroenvironmental factors as ultimate determinants of distribution of common toad and nattejack toad in the south of Spain. -Ecography 19 305-312.We have analysed the relations betwcen the distribution areas of Btfo buju and Birji, calamira in the south of the Iberian Peninsula. In order to chardcterise the localities where the species were found, we used 24 environmental variables. and we tested their influence on the distribution of both species by nonparametric methods. By means of logistic regression we calculated the odds of finding one or other species in a locality. f h e environmental parameters that increase the probability of presence of each species and of both species together are related with the climatic stability and with the climatic subregions. Bufo bufo is more likely to be found in areas where the climate is more predictable, probably because in these areas it may exert its competitive superiority over B. calumiro. In zones with very low climatic stability B. ca/amiru is more likely to be found than B. bifo, probably because B. btc/u lacks the ability to adapt to unpredictable conditions. In areas with intermediate climatic predictability B. bufo is present, but it would be prevented from removing B. culumifu, and so the odds of finding each species are equilibrated. In these areas there would be a balance between the superior competitiveness of B. btgo and the higher adaptability of B. calamira. With the same logistic equation we charwterise the typical habitats of each species, and also the environments shared by both species.

Macroenvironmental factors as ultimate determinants of distribution of common toad and nattejack toad in the south of Spain. -Ecography 19 305-312.We have analysed the relations betwcen the distribution areas of Btfo buju and Birji, calamira in the south of the Iberian Peninsula. In order to chardcterise the localities where the species were found, we used 24 environmental variables. and we tested their influence on the distribution of both species by nonparametric methods. By means of logistic regression we calculated the odds of finding one or other species in a locality. f h e environmental parameters that increase the probability of presence of each species and of both species together are related with the climatic stability and with the climatic subregions. Bufo bufo is more likely to be found in areas where the climate is more predictable, probably because in these areas it may exert its competitive superiority over B. calumiro. In zones with very low climatic stability B. ca/amiru is more likely to be found than B. bifo, probably because B. btc/u lacks the ability to adapt to unpredictable conditions. In areas with intermediate climatic predictability B. bufo is present, but it would be prevented from removing B. culumifu, and so the odds of finding each species are equilibrated. In these areas there would be a balance between the superior competitiveness of B. btgo and the higher adaptability of B. calamira. With the same logistic equation we charwterise the typical habitats of each species, and also the environments shared by both species.

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