Review Reconstructing the soil food web of a 100 million-year-old forest: The case of the mid-Cretaceous fossils in the amber of Charentes (SW France) Sina Adl a, * , Vincent Girard a, b, c , Gérard Breton c , Malvina Lak c , Ardhini Maharning a , Aaron Mills a , Vincent Perrichot c , Maxime Trionnaire c , Romain Vullo c , Didier Néraudeau c a Department of Biology, Dalhousie University, Halifax, Nova Scotia B3H 4J1, Canada b Senckenberg Forschungsintitut und Naturmuseum, Senckenberganlage 25, 60325 Frankfurt am Main, Germany c University of Rennes 1, UMR CNRS 5118, 263 Avenue du Général Leclerc, 35042 Rennes Cedex, France article info Article history: Received 18 May 2010 Received in revised form 30 November 2010 Accepted 4 December 2010 Available online xxx Keywords: Amber Community structure Cretaceous soil Forest ecology Fossil microorganisms abstract Over the past decade, the mid-Cretaceous amber deposits of Charentes (SW France) have been inten- sively studied. The fossils investigated were not only limited to arthropods preserved in amber, but also included microorganisms, plant debris and vertebrate remains. This plethora of analyses provided important data about the ecology of the overall system, including sources of litter input into the soil and of the above-ground ecology. More precisely, they showed that most of the microfossils were those of soil organisms or organisms that participated in the ecology of the forest soil. This new discovery provided the opportunity to study the ecology of the soil as preserved in the 100 million years old Charentes amber. Indeed, the trophic links of the fossil forest soil have been reconstructed on the basis of the fossil assemblage discovered in amber outcrops and overlayed on a model ecological forest soil food web. We relied on existing phylogenetic information to discuss the absence of certain taxonomic groups in the fossilized specimens. Our synthesis shows that although the organisms of this ancient forest of Charentes were different from those of modern soils, the soil food web was organized functionally the same as modern soils. It also demonstrated that trophic links of the soil community were already diverse, including various means of predation, parasitism and organic matter decomposition. The most obvious differences are the absence of evidence for symbiotic root nitrogen fixation and mycorrhizae. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Common attempts at reconstructing ancient forest habitats tend to focus on the above-ground vegetation and animals. Such descriptions have been used to recreate animated documentaries and graphics which can leave a lasting impression with the public. One neglected aspect of these reconstructions is the soil biota. Soils contain a diversity of species that contribute to decomposition of the organic matter and recycling of nutrients into plant available forms. Decomposition provides nutrients that roots compete for, and returns CO 2 to the air for photosynthesis. In addition, there are lessons that can be learned from the fossil record by reconstructing ancient communities, pertinent to our understanding of similar modern habitats (Jackson and Erwin, 2006). Amber is a fossil tree resin that polymerized and fossilized over millions of years. The Charentes region (SW France) is known to be an important area providing amber of mid-Cretaceous age. This amber has been dated to be 100 million years old, from the uppermost Albian to the lowermost Cenomanian (Néraudeau et al., 2002, 2003, 2005, 2008, 2009; Perrichot et al., 2007b), and it has been used to describe many specimens from a variety of taxa. These include fossilized tissue fragments and individuals from prokary- otes and all the eukaryote super-groups of Archaeplastida, Ani- malia, Fungi, Amoebozoa, Stramenopila, Rhizaria, and Excavata (Adl et al., 2005). This review attempts to reconstruct the food web of a forest soil community from fossilized specimens in mid-Cretaceous amber from SW France. One definition used in ecology for soil was proposed by Adl (2003) as “soil is the result of combined mixture of organic matter and unconsolidated minerals and it provides habi- tats for thousands of specific soil species”, which is different from that used in geology and familiar to paleontologists. In this defi- nition, the inorganic part of the soil which is soil texture consists of clay, silt, gravel or sand. The organic part includes the litter such as fallen leaves, woody debris, and animal parts. It also contains secretions and excretions from living organisms such as coprolites * Corresponding author. Tel.: þ1 902 494 2753; fax: þ1 902 494 3736. E-mail address: sadl@dal.ca (S. Adl). Contents lists available at ScienceDirect Soil Biology & Biochemistry journal homepage: www.elsevier.com/locate/soilbio 0038-0717/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.soilbio.2010.12.003 Soil Biology & Biochemistry xxx (2010) 1e10 Please cite this article in press as: Adl, S., et al., Reconstructing the soil food web of a 100 million-year-old forest: The case of the mid-Cretaceous fossils in the amberof Charentes(SW France), Soil Biology & Biochemistry (2010), doi:10.1016/j.soilbio.2010.12.003