Skip to main content

Post-glacial recolonisation and Holocene anthropization impact on populations of shrews and hedgehogs from Western Europe inferred from zooarchaeology, historical biogeography and ecological modeling

Final Report Summary - SMALL_MAM_RECOL (Post-glacial recolonisation and Holocene anthropization impact on populations of shrews and hedgehogs from Western Europe inferred from zooarchaeology, historical biogeography and ecological modeling)

This 24-month Marie Curie (MC) Project (PIEF-GA-2013-629604) was intended to reconstruct the process of post-glacial recolonization of several species of shrews and the European hedgehog in Western Europe on the basis of geo-referenced and well dated occurrences. Also, as main objectives, we wanted to integrate our results into those of environment and coastlines, and to understand in which extent the Holocene accelerated anthropisation affected the past and current distributions of the studied species. Finally, if possible, we would like to contribute to general management and conservation policies of the studied species.

In order to achieve these aims, we proposed a series of operational objectives, including: 1) the re-examination of key fossil small mammal collections from Western Europe in search of shrew and European hedgehog remains to obtain an appropriate zooarchaeological corpus; 2) the discrimination among very close species of shrews through the use of geometric morphometrics; 3) the direct radiocarbon dating of insectivore bones to get a precise chronological framework; 4) taking advantage of the Inventaire Archéozoologique et Archéobotanique de France (I2AF) and the Inventaire National du Patrimoine Naturel (INPN) databases, both hosted at the MNHN; 5) taking advantage of the extensive background on molecular phylogeography and the assistance of key scholars; 6) applying cutting-edge tools for spatial analysis and ecological niche modeling.

MC fellow is Juan Rofes (JR) and scientist in charge is Anne Tresset (AT).

Regarding the general program, we have fulfilled most of the operational objectives proposed in original project and we are in the right path to accomplish main goals as well. (1) We have gathered and successfully reviewed the material of 35 different archaeological sites (geographically and chronologically referenced) from all across French territory and abroad, with chronologies spanning from Magdalenian up to historical times. (2) JR has done a detailed inventory with all the previous data; this inventory is (and will be) the baseline to reconstruct the post-glacial recolonization process of several species of shrews and the European hedgehog in Western Europe. (3) Through JR contacts in Spain, we had access to data and materials of archaeological sites from the Iberian Peninsula (Late Pleistocene to Holocene), which is one of the main sources for north-western Europe post-glacial recolonization of insectivores. In particular, we got materials for comparison from the sites of Alorda Park (Barcelona, Iron Age), El Portalón (Burgos, Chalcolithic), Antoliñako Koba and Santimamiñe (Bizkaia, Late Pleistocene), and Artazu (Gipuzkoa, Late Pleistocene). (4) JR has reviewed and snapshot hundreds of specimens from South- and Eastern Europe stored at Charles University in Prague; Southern and Eastern Europe are also important sources for north-western Europe post-glacial recolonization. (5) JR have snapshot and land marked (with TPS software) dozens of specimens of Crocidura suaveolens (modern and archaeological) from many insular and continental sites in Western Europe (France, UK, and Spain). Also, he has land marked (and incorporated into the analyses) specimens from Mediterranean islands (Corsica, Karpathos and Cyprus) and Eastern Europe (south Italy, Serbia, and Turkey). (6) JR has been successfully trained in geometric morphometrics (GMM) theory and practice by Drs. Raphaël Cornette and Thomas Cucchi (TC) during the first year, and exclusively by TC during the second year of the project. (7) Additionally and complementarily, JR has taken 2 seminars (Montpellier and Barcelona) recommended by TC, specifically dedicated to statistical analyses with GMM data. (8) JR has thoughtfully applied those statistical techniques and training (through Morpho-J, PAST and R packages) to the data on shape and size obtained with C. suaveolens past and recent populations from Western Europe, Eastern Europe and the Mediterranean. (9) Based on previous literature, two different anatomical sections of the mandible (posterior half of the mandible in medial view and condyle in posterior view) were statistically tested to identify which was the most useful to discriminate populations. We used a landmark approach for the posterior half of the mandible and a semi-landmark approach for the condyle. (10) The posterior part of the mandible proved to be much more useful for segregating populations in terms of shape, presenting a biogeographical coherence as well, as shown by several statistical analyses (PCA, LDA, CVA, and Mahalanobis distances, among others). (11) Regarding size (log of centroid size), we tested and found the effects of insular syndrome (i.e. larger size) in populations coming both from North Atlantic and Mediterranean islands, a phenomena poorly studied in shrews up to now. A number of tests (T-test, F-test, ANOVA, Turkey’s pairwise, and Bonferroni) have been performed in order to quantify the difference between insular and continental populations. (12) The correlation between shape and size of the mandibles and environmental/geographic constrains (as the distance of islands to continent and their different areas) has been also tested for significance by means of regression analysis. (13) JR has been successfully trained in the use and dynamics of the I2AF databases by Dr. Cécile Callou. During these 2 years we have taken numerous references and distribution maps from those databases, and we are now able to contribute to them with numerous new entries. (14) JR has collected dozens of references on molecular and historical biogeography of shrews and hedgehogs; AT and JR are in permanent contact with Dr. Allan McDevitt (University College Dublin) regarding molecular phylogeography of genus Crocidura. (15) Incorporation of Dr. Jerry Herman (Department of Natural Sciences, National Museums of Scotland) during second year has been a milestone in the phylogeography front of the project, as he is bringing all his expertise on insularity and biogeography of soricids to our project. (16) Data on coastlines evolution contributed by Dr. Pierre Stephan (LETG lab, European Institute of Marine Science) and his expertise will be key to understand shape and size differences among different North Atlantic island populations as a function of their precise moment of isolation from the continent (and among them) since the beginning of the Holocene global warming and subsequent marine transgression leading to territorial fragmentation. (17) With all the samples of C. suaveolens (both modern and archaeological) that we have gotten up to now and that we already have processed with our GMM approaches together with phylogeographic data contributed by Jerry Herman and coastline evolution data given by Pierre Stephan, we will write a scientific paper whose structure is already designed by JR, AT and TC. It will be most likely sent to the prestigious Journal of Biogeography. (18) This latter paper will address the following question: Is C. suaveolens a native species in the small islands of northwestern Europe (Molène Archipelago, Ouessant, Scilly, and others)? The answer is key in the frame of our project on the post-glacial recolonization of soricids into north-west Europe from glacial refuges. If C. suaveolens is indeed native to these islands, which constitute the northern limits of its current distribution, this gives an ante quem for its arrival into the region. It should predate the period when Scilly and Ouessant got isolated from the continent (ca. 11.500 years ago), an event resulting from the sea-level uprising (due to ice melting) during the Holocene climatic optimum. (19) JR, TC and AT successfully presented preliminary results of all this work to the Association for Environmental Archaeology (AEA) Spring Meeting (Islands: Isolation and connectivity, 1-5 April 2016) in Kirkwall, Orkney Island, UK, having a productive feedback from the international audience. (20) JR hosted a 3-month research visit of a PhD student (Aitziber Suárez Bilbao, University of Basque Country UPV-EHU) during second year. Under his supervision, ASB did hundreds of snapshots of Neomys mandibles from the collections of MNHN, subsequently land marking them for GMM analyses. (21) JR successfully trained ASB in basic theory and practice of GMM, fulfilling the MC expectancy of international collaboration among institutions, interchange of students and transfer of knowledge. (22) JR and ASB succeed in segregating Neomys fodiens from N. anomalus mandibles with a semi-landmark approach using condyles in posterior view. Distinguishing these two closely related species in archaeological and paleontological contexts have previously proved to be impossible through morphoscopic and morphological approaches. Being therefore these results of general interest for archaeologists and paleontologists, they will be submitted to a scientific journal in a close future. (23) Establishing a clear and trustable difference between the two European species of Neomys is the first unavoidable condition for studying the post-glacial recolonization process of each species separately. (24) JR and AT have permanently contributed —with materials and advice— to the process of testing protocols for the miniaturization of collagen extractions (with the ultimate goal of radiocarbon dating shrew remains), a specific task undertaken by Drs. Sophie Cersoy (SC) and Antoine Zazzo (AT). (25) During second year all protocols were successfully tested by SC and pre-screening for collagen contents was performed. (26) According to FTIR estimations, all the archaeological samples provided by JR had collagen enough (i.e. more than 0.5 mg) for AMS radiocarbon dating, and precise dates were obtained. (27) Being this methodological approach (for radiocarbon dating extremely small quantities of collagen) completely new and ground-breaking for the scholar community, a scientific paper coauthored by SC, JR, AZ and others was prepared and submitted to the prestigious journal Radiocarbon. This paper will be published very soon after minor corrections.

After 2 years of project, there is only one operational objective that was not fulfilled: the ecological modeling. For reasons out of control of JR and AT, it was absolutely impossible for JR to get trained in this discipline and subsequently apply it to our corpus of data.

In summary, given the large amount of work performed up to now, and the realistic projections for the following months, we can say that we are in the right path to fulfill all our main objectives, including the reconstruction of northwestern Europe recolonization processes of soricids from glacial refuges, measuring the effects of anthropization and environmental constrains in such processes, and contributing to the general management and conservation of the studied species. We will definitely begin with results for the taxa Crocidura suaveolens and Neomys, which are currently under production.