Factors affecting the geographic distribution of the family Turdidae in the Iberian Peninsula
Published: Volume 53(1), June 2006. Pages 127-141.
Original Title: Determinantes de la distribución geogrÁfica de la familia Turdidae en la península Ibérica
Aims: To analyze the environmental factors influencing the large-scale distribution of 17 breeding species of Turdidae in the Iberian Peninsula. To test the predictions of global climatic change and the hypothesis of "abundance centers" on the frequency of occurrence of these species within the Iberian Peninsula.
Methods: The frequency of occurrence of each species in UTM squares of 10 x 10 km within blocks of 50 x 50 km was modeled by means of regression tree analyses using 26 geographic, climatological and land-use variables. Residuals of these models in each one of the 190 blocks of 50 x 50 km (i.e., distribution patterns in Iberia not related to autoecological-environmental preferences) were related to the distances to the European barycenter of each species.
Results: The models summarizing the basic environmental preferences of the 17 species accounted for an average 78.3 % of variation in the frequency of occurrence within the Iberian Peninsula. There was a common selection for areas located at higher altitudes or in mountains, the avoidance of agricultural landscapes, and a tight relationship with climatic variables (especially insolation). The frequency of occurrence of the 17 turdid species in Spain was not markedly influenced by the distances to their European distribution barycenters.
Conclusions: The large-scale distribution patterns of the 17 turdid species in the Iberian Peninsula can be adequately explained considering coarse-grained environmental variables. Climatic variables were highly influential, although their effects do not support current predictions on alteration of distribution patterns due to global warming. After controlling for autoecological-environmental preferences, the hypothesis of "centers of abundance2 did not play any role in determining the distribution patterns in the Iberian Peninsula.