Predictable structure of Miocene insectivore (Lipotyphla) faunas in Western Europe along a latitudinal gradient Marc Furió a, ⁎, Isaac Casanovas-Vilar a , Lars W. van den Hoek Ostende b a Institut Català de Paleontologia, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Spain b Netherlands Centre for Diversity Naturalis, Leiden, The Netherlands abstract article info Article history: Received 31 August 2009 Received in revised form 15 December 2009 Accepted 30 January 2010 Available online 6 February 2010 Keywords: Lipotyphla Nested subsets Species composition Paleobiogeography Micromammals Iberian Peninsula Paleoclimate Paleohumidity The insectivores (Grandorder Lipotyphla) have been seldom used in mammal-based paleoenvironmental inferences because this group is generally considered insufficiently represented or studied. Nevertheless, a recent compilation on the insectivore record of Western Europe has shown that this is not the case. From the insectivore occurrences themselves a major paleobiogeographical pattern seems to be present: the faunas of the Mediterranean regions of Western Europe are poorer and seem to be a subset of those occurring at higher latitudes. This kind of pattern, where smaller assemblages seem to be a ‘nested subset’ of the richer ones, is known as nestedness. In this work we analyze the prevalence of nestedness in the Miocene insectivore record of western Europe. The calculations are carried separately for each MN (Mammal Neogene) zone and a measure of nestedness or order is given. The probability that a similarly nested pattern could be obtained at random for each MN is assessed by permutation. Our results show the prevalence of nestedness in all the MN zones except the MN 1. In the second step, we study the causes of nestedness. A significant correlation of the nested structure with latitude is found in 8 out of 12 matrices, thus confirming that the southern assemblages are a subset of the northern ones. This must be related to some underlying latitudinal gradient that already existed during the Miocene. Latitudinal gradients in temperature seem to have been unimportant until the Late Miocene yet the nested pattern existed as early as the Early Miocene. A precipitation gradient, which was already present by the Early Miocene, seems to be the most important structuring factor. Independent evidence has confirmed that the Central European regions were more humid than the Mediterranean ones thus explaining the higher diversity of insectivores in that area as this group is more diverse in humid climates. The structure of the southern assemblages is a highly predictable subset of that of the northern ones. In the south the species that seem to have required higher levels of environmental moisture are missing. This applies for instance to many talpids and dimylids which never reached the Iberian Peninsula. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Paleontologists working on small mammals often see the insecti- vores as the ‘poor fellows’ of rodents. This mammalian order is much less common and diverse than that of rodents and has been regrettably overlooked during decades, even though sufficiently complete collec- tions were available. The introduction of field methods for gathering huge small-mammal samples (see Daams and Freudenthal, 1988 for a review) triggered the application of rodents in paleoecology and biostratigraphy. Rodents were used to define and characterize biochro- nological or biostratigraphical units (for early examples see Mein, 1975; Daams et al., 1977) and their cheek teeth were counted in a similar fashion as pollen grains for inferences on paleoclimatology (see Van de Weerd and Daams, 1978 for the first application of this methodology). Even though their value as paleoenvironmental indicators was usually recognized, the insectivores were generally excluded from these analyses well until the 2000s (see Van den Hoek Ostende, 2001b; Van Dam, 2006; Van Dam et al., 2006; García-Alix et al., 2008). The emergence of the insectivores in paleoecological studies is probably related to previous demonstrations of their sensitiveness and depen- dence on physical environmental conditions (Reumer, 1989, 1995; Rzebik-Kowalska, 1995; Hernández Fernández, 2001). Even so, insecti- vores are generally used indiscriminately. The proportion of the group relative to rodents is considered a proxy for humidity. However, there are indications – in fact justified in the present paper – that some genera were more resilient to drier conditions than others. As for the use of insectivore taxa for biostratigraphical/biochrono- logical purposes, they are not generally considered in the definition of local or regional chronological divisions, even though they have been included in some charts (see for example Van Dam et al., 2001). The claims that this group is insufficiently known and/or represented are often used to justify their exclusion (see for example De Bruijn et al., 1992). In order to emend this perceived misconception, a group of Palaeogeography, Palaeoclimatology, Palaeoecology 304 (2011) 219–229 ⁎ Corresponding author. Marc Furió, Institut Català de Paleontologia, Universitat Autònoma de Barcelona, Edifici ICP, Campus de la UAB s/n, E-08193 Cerdanyola del Vallès, Barcelona, Spain. Tel.: +34 935868331; fax: +34 935868333. E-mail address: marc.furio@icp.cat (M. Furió). 0031-0182/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.palaeo.2010.01.039 Contents lists available at ScienceDirect Palaeogeography, Palaeoclimatology, Palaeoecology journal homepage: www.elsevier.com/locate/palaeo