Understanding parapatry: How do environment and competitive interactions shape Iberian vipers’ distributions?

Aim: To assess if the parapatry of the three viper species present in the Iberian Peninsula is mainly caused by environmental conditions, historical events, interspecific competition among them, or a combination of these factors. Location: The Iberian Peninsula Taxon: Vipera aspis, V. latastei, and V. seoanei. Methods: We applied the concept of favourability of occurrence to produce commensurate distribution units unaffected by the prevalence of different species in the Iberian Peninsula. We compared the favourability of each species individually with the favourability of occurrence of more than one species co-occurring in their overlapping ranges, and identified the areas in which sympatric coexistence, environmental segregation, and competitive exclusion are predicted to occur. Results: The main driver of the parapatric pattern was competitive exclusion, which was mediated by gradual changes in the environmental conditions favouring each species. The para-Mediterranean V. ...