Abstract
Numerous Pliocene large-mammal assemblages have been discovered in Chad over the last decade. They offer a unique opportunity to understand the settings in which important chapters of Hominid evolution took place in Central Africa. However, it is crucial to first investigate both sampling and taxonomic homogeneity for these Chadian assemblages because they occur over large sectors in a sandy desert that offers virtually no stratigraphic section. Using cluster analysis and ordination techniques, we show that the three Pliocene sectors from Chad are homogeneous and adequate sampling units. Previous stable isotope analyses on these assemblages have indicated that the environment became richer in C4 plants between approximately 5.3 and 3.5–3 Ma. To test whether this environmental change has affected the structure of palaeo-communities, we assigned body mass, trophic and locomotor eco-variables to mammal species from the three sectors. Statistical analysis shows that the overall ecological structure of the assemblages is not linked with the opening of the plant cover, and eco-variables show no temporal trend from the oldest sector to the youngest. For example, there is no significant change in the relative diversity of grazing and browsing taxa, although mixed feeders are less diversified in the youngest sector than in the preceding one. This pattern apparently does not result from potential biases such as methodological artefacts or taphonomic imprint. Instead, it seems that local heterogeneous environmental factors have played a major role in shaping the ecological spectrum of Chadian mammal palaeo-communities during the Pliocene.
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Acknowledgements
We thank the Chadian authorities [Ministère de l'Education Nationale, de l'Enseignement Supérieur et de la Recherche (MENESR), Université de N'Djaména and Centre National d'Appuià la Recherche (CNAR)], the French Ministère des Affaires Etrangères and the Université de Poitiers. This study is part of the Centre National de la Recherche Scientifique (CNRS) Eclipse II and of the National Science Foundation/Revealing Hominid Origins Initiative (NSF/RHOI) programmes. E.F. acknowledges a CNRS post-doctoral fellowship. We thank all the members of the MPFT for work in the field and taxonomic identifications as well as M.A. Buzas and three anonymous reviewers for their comments on the manuscript.
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Fara, E., Likius, A., Mackaye, H.T. et al. Pliocene large-mammal assemblages from northern Chad: sampling and ecological structure. Naturwissenschaften 92, 537–541 (2005). https://doi.org/10.1007/s00114-005-0041-6
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DOI: https://doi.org/10.1007/s00114-005-0041-6