Early-Middle Pleistocene structural changes in mammalian communities from the Italian peninsula

The late Early and Middle Pleistocene mammal fossil record of Italy has been revised by grouping faunal lists into discrete faunal complexes, termed cluster units, by means of bootstrapped cluster analysis which allows the evaluation of group partition sharpness. These complexes have been compared with previously erected Italian biochrons and then analysed for their body size (by cenogram analysis) and diversity trends. Some considerations about changes in predator-prey ratios are made. It is shown that diversity increased sharply at the onset of the middle Galerian mammal age, coincident with the well-known shift from 40 to 100 ka glacial-interglacial periodicity. This increased diversity was entirely driven by the concurrent arrival in Italy of some large ungulates. Cenograms reveal that the climate became wetter and markedly cooler following the and conditions that characterize the late Early Pleistocene. Wetter environments are generally expected to sustain a higher proportion of large herbivore species. Because carnivore species did not respond in the same way, the predator-prey ratio changed in favour of prey. In summary, the transition from Early to Middle Pleistocene faunas (from early to middle Galerian mammal ages) represents a major reorganization in the large-mammal complexes from the Italian peninsula. This was reflected in both the diversity and trophic structure of large-mammal communities.