Exploring paleo food-webs in the European Early and Middle Pleistocene: A network analysis

Food webs are networks of feeding (trophic) interactions among species. As any other network approach, research on food webs focuses its analysis on the structure of direct and indirect interactions among diverse species, rather than looking at the particularities of certain taxa. In recent times, scholars have collected an impressive amount of empirical food-web data to study present day terrestrial and aquatic habitats. More restrictively, this approach has also been applied to trophic interactions represented in the fossil record of extinct ecosystems. Nevertheless, to our knowledge, none of them has addressed the role played by the different Pleistocene hominin species as part of such food-webs. In this work, we aim at filling this gap by focusing on the Early and Middle Pleistocene paleo-communities in Western Eurasia. Our goal is to improve our understanding on changes experienced by large mammals' interactions during this period, and shed some light on the influence of and on Homo species of those changes. We have constructed up to 27 paleo food-webs from the archaeo-paleontological record of European assemblages, covering from the Middle Villafranchian to the Late Galerian. Only large mammals have been considered, including a couple of Homo species that are present in 8 food-webs. Then, we have developed a two-steps analysis. First, we have calculated the main structural features of all the networks, and have compared them across geographical areas, periods and cases with and without Homo species. Second, we have calculated different structural centrality measures in order to assess the relevance of Homo species in their corresponding food-webs. The obtained results show that the Pleistocene food webs under study shared basic features with modern food webs, although differences in the values of some parameters might be significant. Moreover, when comparing the networks across periods, we found a marked change that could be related to the Mid-Pleistocene Revolution. Finally, our results also highlight the trophic position of hominins in the web as a central species that channeled energy fluxes. (C) 2015 Elsevier Ltd and INQUA. All rights reserved.