Aim: As parapatric distributions are traditionally studied by pairs of species, this study aims to evaluate the causes of the maintenance of parapatry, specifically to assess whether the case 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. aspis presented fragmented favourable areas outside its range that seemed to be unoccupied due to competitive exclusion by the other vipers.The Mediterranean V. latastei appeared to be limited by competition with the other viper species and by the environment in north-western Iberia. V. seoanei prevented the other two species becoming established in the north-western quarter of the Iberian Peninsula due to its better adaption to the humid conditions in this region. Some areas of sustainable coexistence were detected, mainly in the upper reaches of the River Ebro. Main conclusions:Each species is better adapted to particular conditions. However, the existence of ecotones forces them to occur sympatrically and compete for resources. The parapatric pattern is a result of the evolutionary history of the species and of strong competitive interactions between them, which form 'competitive-exclusion barriers'. However, these barriers are environmentally dependent, so changes in the environment could rapidly affect the limits of the species distribution. K E Y W O R D S biogeography, distribution boundaries, interspecific competition, parapatric species, Vipera | 1323 CHAMORRO et Al. B I OS K E TCH Darío Chamorro is a PhD candidate at Biogeography, Diversity and Conservation research group (https://bioge ograf ia-uma. com/, Universidad de Málaga, Spain) interested in the factors that produce the biogeographical patterns of species distribution and their dynamics, on an ongoing global change context and with special concern for conservation. Author contributions: D.C. analysed the data; D.C. and A.-R.M.

Winters have become warmer under the impact of climate change, which has modified the phenology as well as the distribution ranges of birds. The African Long‐legged Buzzard Buteo rufinus cirtensis has recently colonized Europe via the Strait of Gibraltar. We aim to explain the native distribution of this species and to predict favourable areas in newly colonized parts of Europe using geospatial modelling to identify the most influential factors in this process. We applied the favourability function, a generalized linear model describing environmental favourability, for the presence/absence of breeding areas in northern Morocco and the southern Iberian Peninsula, according to a set of variables describing climate, topography, human activity, vegetation and purely spatial trends. A model was built using some known breeding sites in northern Morocco, and was used to forecast future suitable breeding areas in Europe. A second model was built with the available data for northern Morocco and Europe to explain the current distribution of breeding sites. Both models were assessed according to discrimination, calibration and parsimony criteria, and the influence of each factor was analysed using variation partitioning. We conclude that the Iberian Peninsula could provide new suitable areas for the species and facilitate its northward expansion. This result, together with the increasing number of records available, suggests that this species could soon spread throughout Europe. Steady temperatures and abundant but seasonally distributed precipitation showed the strongest predictive power in the models. This indicates a close relationship between the species’ distribution and climate in the study area, and suggests that this species finds its most favourable environments in the Mediterranean biome. Topography and vegetation, specifically cliffs and woods near hunting zones, point to a fine‐scale habitat selection for breeding. As the case of the African Long‐legged Buzzard is not a unique event, our results may be useful to determine whether a northward expansion of the Mediterranean biome could be followed by distribution shifts of bird species that have so far been restricted to Africa.

The recent modification of species distribution ranges in response to a warmer climate has constituted a major and generalized biogeographic change. The main driver of the shift in distribution is the disequilibrium of the species ranges with their climatic favourability. Most species distribution modelling approaches assume equilibrium of the distribution with the environment, which hinders their applicability to the analysis of this change. Using fuzzy set theory we assessed the response to climate change of a historically African species, the Atlas Long-legged Buzzard. With this approach we were able to quantify that the Buzzard’s distribution is in a latitudinal disequilibrium of the species distribution with the current climate of 4 km, which is driving the species range northwards at a speed of around 1.3 km/year, i.e., it takes 3 years for the species to occupy new climatically favourable areas. This speed is expected to decelerate to 0.5 km/year in 2060–2080.

Background: The current modification of species distribution ranges, as a response to a warmer climate, constitutes an interesting line of work and a recent challenge for biogeography. This study aimed to determine if the climatic conditions of southern Europe are adequate to host a typical African species, the House Bunting, which is registered regularly during the last years, still in low numbers. To this end, the distribution of the species in its native range was modelled, both in the present and in future climate scenarios, using its current breeding distribution areas and a set of environmental variables. Results: The results showed that the southern half of the Iberian Peninsula exhibits high values of favourability to host this African species for the current climatic conditions. Furthermore, future forecasts indicated an increase in favourability for this area. The favourable areas we detected in the south of the Iberian Peninsula are already regularly receiving individuals of the species. These observations are very likely vagrant birds dispersing from recently colonised breeding areas in northern Morocco, which may indicate a continuous process of colonisation towards the north, as has occurred during the last decades in Northern Africa. Conclusions: We cannot anticipate when the House Bunting will establish on the European continent because colonisation processes are usually slow but, according to our results, we predict its establishment in the near future. We have also identified those areas hosting favourable conditions for the species in Europe. These areas are a potential focal point for the colonisation of this and other African birds if the climate continues to warm.

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