National parks play a key role in preserving representative natural landscapes for future generations. Understanding the spatial patterns of biodiversity and their underlying processes is a fundamental task for conservation biology. This is specially relevant for top predators, which rather than being a simple “aesthetic” component to conserve, have been recently demonstrated to be: 1) the most sensitive trophic level to environmental changes, and 2) highly relevant for ecosystem functioning, being their extinction a cause for extremely important changes in functions such as disease dynamics, wild fires and biogeochemical cycles. Among terrestrial predators, spiders are the most abundant and diverse group on Earth. Despite their abundance and pivotal role in ecosystem functioning, spiders remain poorly known and consequently are often neglected in biodiversity conservation policies. This lack of knowledge compromises the correct assessment of the representativeness and complementarity of protected areas, which are essential in establishing conservation priorities. Here we propose to circumvent these limitations by combining standarized sampling protocols developed for Mediterranean spiders with modern DNA based taxonomic techniques to gain a better understanding of the diversity of spiders in the Iberian peninsula and their biogeographic and evolutionary patterns. DNA barcoding uses standardized 500- to 800-bp sequences to accelerate and automatize species identification. In addition, DNAbarcodes help to reveal biogeographic history and refine species distributions by providing information on phylogenetic relationships and population structures and allowing identification of immature stages. Spiders are among the most diverse and ubiquitous organisms on Earth, are easy to sample and play an important role in shaping arthropod communities as the dominant predators in most terrestrial ecosystems. Because of their sensitivity to environmental changes and anthropogenic impacts, spiders have been identified as promising bioindicators. In this study, we propose to conduct semi-quantive sampling in 6 Spanish national parks, roughly representing a latitudinal and longitudinal biogeographic and climatic gradient. We will focus our sampling efforts on white oak forests because they are among the most representative Iberian forests, show high levels of endemicity, are of conservation concern, and their evolutionary history in the peninsula is relatively well-known.  We will address specific question regarding the assembly of spider communities of white of forest in a phylogenetic framework. We will specifically test if (1) climate is the main driver shaping local spider communities, (2) spider communities in recent post-glacial forests show a higher ratio of immigrant species and (3) functional diversity among forest types and parks remains constant as a results of replacement of functionally similar groups. The results of the project will greatly improve our current knowledge of the diversity and distribution of a key component of terrestrial ecosystems and will provide important information on the fine scale biogeographic patterns and main drivers of diversification of one of the richest and highly endemic yet increasingly vulnerable fauna in Europe.