Biogeographic regions of the Iberian Peninsula: butterflies as biogeographical indicators

The objective definition of geographic regions based on biotic criteria is useful for summarizing biodiversity as well as for predicting the geographically differential effects of general trends and for planning an adequate distribution of the protected areas. We propose a regionalization of the Ibero-Balearic area based on butterfly presence-absence data and a synthesis of several clustering methods (similarity, parsimony analysis and multivariate techniques), and characterize the sub-regions on the basis of diagnostic species. Seven regions are proposed. The results showed two basic gradients, which apparently lead the butterfly species distributions within the study area: a north-east-south-west one, related to altitude and species richness, and a west-east one, implying a humidity or lithologic gradient. The Balearic Islands remain as an independent region in all cases. The observed divisions probably reflect the distribution of species richness in the study area. Characteristic species for each of the regions were identified using a numerical preference index. The network of protected areas is well represented in all of the sectors proposed, although three of the proposed sub-sectors are under-represented if sampling effort is taken into consideration.