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Updated distribution and biogeography of amphibians and reptiles of Europe

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  • 1 1Centro de Investigação em Ciências Geo-Espaciais, Alameda do Monte da Virgem, 4430-146 Vila Nova de Gaia, Portugal
  • | 2 2Department of Earth and Environmental Sciences, Università di Milano-Bicocca, Piazza della Scienza 1, 20126 Milano, Italy
  • | 3 3Museo di Storia Naturale dell’Università di Firenze, Sezione di Zoologia “La Specola”, Via Romana 17, 50125 Firenze, Italia
  • | 4 4RAVON, Postbus 1413, 6501 BK Nijmegen, The Netherlands
  • | 5 5CNRS-UMR5175 CEFE, Centre d’Ecologie Fonctionnelle et Evolutive, 1919, route de Mende, 34293 Montpellier, France
  • | 6 6Department of Biology and Ecology, Faculty of Sciences and Mathematics, University of Niš, Višegradska 33, 18000 Niš, Serbia
  • | 7 7Department of Evolutionary Biology, Institute for Biological Research “Siniša Stanković”, University of Belgrade, Despota Stefana 142, 11000 Beograd, Serbia
  • | 8 8F.R.S. – FNRS Research Associate, Behavioural Biology Unit, University of Liège, 22 Quai van Beneden, 4020 Liege, Belgium
  • | 9 9CIBIO, University of Porto, R. Campo Alegre 687, 4169-007 Porto, Portugal
  • | 10 10Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow 117071, Russia
  • | 11 11Natural History Museum of Crete, University of Crete, Knossou Ave., P.O. Box 2208, 71409 Heraklion Crete, Greece
  • | 12 12Faculty of Life Sciences and Engineering, Universitat de Lleida, Av. Rovira Roura 191, 25198 Lleida, Spain
  • | 13 13Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Animal Phylogeny and Systematics, Passeig Marítim de la Barceloneta 37-49, 08003 Barcelona, Spain
  • | 14 14Technische Universität Braunschweig, Division of Evolutionary Biology, Zoological Institute, Mendelssohnstr. 4, 38108 Braunschweig, Germany
  • | 15 15c/o Museo Civico di Storia Naturale, via San Francesco di Sales 88, 10022 Carmagnola (TO), Italia
  • | 16 16Research Institute for Nature and Forest, Kliniekstraat 25, 1070 Brussels, Belgium
  • | 17 17University of Twente, Faculty of Geo-Information Science and Earth Observation (ITC), P.O. Box 217, 7500 AA Enschede, The Netherlands
  • | 18 18Museo Nacional de Ciencias Naturales and Consejo Superior de Investigaciones Científicas, c/José Gutierrez Abascal 2, 28006 Madrid, Spain
  • | 19 19REFER Biodiversity Chair, University of Porto, CIBIO, Campus Agrário de Vairão, R. Padre Armando Quintas, 4485-661 Vairão, Portugal
Open Access

A precise knowledge of the spatial distribution of taxa is essential for decision-making processes in land management and biodiversity conservation, both for present and under future global change scenarios. This is a key base for several scientific disciplines (e.g. macro-ecology, biogeography, evolutionary biology, spatial planning, or environmental impact assessment) that rely on species distribution maps. An atlas summarizing the distribution of European amphibians and reptiles with 50 × 50 km resolution maps based on ca. 85 000 grid records was published by the Societas Europaea Herpetologica (SEH) in 1997. Since then, more detailed species distribution maps covering large parts of Europe became available, while taxonomic progress has led to a plethora of taxonomic changes including new species descriptions. To account for these progresses, we compiled information from different data sources: published in books and websites, ongoing national atlases, personal data kindly provided to the SEH, the 1997 European Atlas, and the Global Biodiversity Information Facility (GBIF). Databases were homogenised, deleting all information except species names and coordinates, projected to the same coordinate system (WGS84) and transformed into a 50 × 50 km grid. The newly compiled database comprises more than 384 000 grid and locality records distributed across 40 countries. We calculated species richness maps as well as maps of Corrected Weighted Endemism and defined species distribution types (i.e. groups of species with similar distribution patterns) by hierarchical cluster analysis using Jaccard’s index as association measure. Our analysis serves as a preliminary step towards an interactive, dynamic and online distributed database system (NA2RE system) of the current spatial distribution of European amphibians and reptiles. The NA2RE system will serve as well to monitor potential temporal changes in their distributions. Grid maps of all species are made available along with this paper as a tool for decision-making and conservation-related studies and actions. We also identify taxonomic and geographic gaps of knowledge that need to be filled, and we highlight the need to add temporal and altitudinal data for all records, to allow tracking potential species distribution changes as well as detailed modelling of the impacts of land use and climate change on European amphibians and reptiles.

Abstract

A precise knowledge of the spatial distribution of taxa is essential for decision-making processes in land management and biodiversity conservation, both for present and under future global change scenarios. This is a key base for several scientific disciplines (e.g. macro-ecology, biogeography, evolutionary biology, spatial planning, or environmental impact assessment) that rely on species distribution maps. An atlas summarizing the distribution of European amphibians and reptiles with 50 × 50 km resolution maps based on ca. 85 000 grid records was published by the Societas Europaea Herpetologica (SEH) in 1997. Since then, more detailed species distribution maps covering large parts of Europe became available, while taxonomic progress has led to a plethora of taxonomic changes including new species descriptions. To account for these progresses, we compiled information from different data sources: published in books and websites, ongoing national atlases, personal data kindly provided to the SEH, the 1997 European Atlas, and the Global Biodiversity Information Facility (GBIF). Databases were homogenised, deleting all information except species names and coordinates, projected to the same coordinate system (WGS84) and transformed into a 50 × 50 km grid. The newly compiled database comprises more than 384 000 grid and locality records distributed across 40 countries. We calculated species richness maps as well as maps of Corrected Weighted Endemism and defined species distribution types (i.e. groups of species with similar distribution patterns) by hierarchical cluster analysis using Jaccard’s index as association measure. Our analysis serves as a preliminary step towards an interactive, dynamic and online distributed database system (NA2RE system) of the current spatial distribution of European amphibians and reptiles. The NA2RE system will serve as well to monitor potential temporal changes in their distributions. Grid maps of all species are made available along with this paper as a tool for decision-making and conservation-related studies and actions. We also identify taxonomic and geographic gaps of knowledge that need to be filled, and we highlight the need to add temporal and altitudinal data for all records, to allow tracking potential species distribution changes as well as detailed modelling of the impacts of land use and climate change on European amphibians and reptiles.

Introduction

A good knowledge on the geographical distribution of organisms is pivotal for macro-ecological and evolutionary studies, as well as to inform policy makers in decisions on land management, health, climate change and biodiversity conservation (Jetz, McPherson and Guralnick, 2011). The availability of reliable maps that depict the historical and current distribution of species therefore constitutes an important component in conservation-related research. Data on their extent of occurrence are crucial for assigning IUCN threat categories to species (IUCN, 2001). This has for instance been a strategy in the Global Amphibian Assessment (Stuart et al., 2004) which provided the first comprehensive estimate of threat categories and distribution ranges of amphibians worldwide, a taxon that constitutes an important model group in conservation biology (e.g. Hopkins, 2007). Furthermore, many amphibian species and at least some groups of reptiles are undergoing severe global declines (Wake and Vredenburgh, 2008; Sinervo et al., 2010; Böhm et al., 2013), making their conservation a prime challenge and gathering data on their current distribution a top research priority.

In European herpetology, shortly after the Societas Europaea Herpetologica (SEH) was established in 1979, it became evident that a comprehensive assessment of the distribution of all European amphibians and reptiles should receive priority, as basic maps where lacking. A mapping committee of the SEH was established in 1983, coordinated by a team based at the Muséum National d’Histoire Naturelle in Paris. From the work of regional and national coordinators, more than 85 000 grid records were collected and shown in maps of 50 × 50 km resolution produced by the Service du Patrimoine Naturel (Paris, France). This resulted in a distribution atlas published in 1997 (Gasc et al., 1997). This work, which in the following will for brevity be referred to as ‘the 1997 European Atlas’, has subsequently provided the basis for numerous studies, such as several conservation-oriented modelling approaches (e.g. Araújo and Pearson, 2005; Araújo et al., 2005; Araújo, Thuiller and Pearson, 2006; Araújo et al., 2008).

After the publication of the 1997 European Atlas, there has been a high intensity of mapping efforts and related research in Europe. Numerous regional and national societies have since then produced detailed amphibian and reptile distributional information covering large parts of Europe, more detailed and reliable than the 1997 European Atlas. Many of these were published in the form of regional or national atlases (e.g. Bitz et al., 1996; Günther, 1996; Pleguezuelos, 1997; Cabela, Grillitsch and Tiedemann, 2001; Hofer, Monney and Dušej, 2001; Pleguezuelos, Lizana and Márquez, 2002; Głowaciński and Rafiński, 2003; Puky, Schad and Szövenyi, 2006; Sindaco et al., 2006; Jacob et al., 2007; Lanza et al., 2007; Laufer, Klemens and Sowig, 2007; Proess, 2007; Creemers and van Delft, 2009; Corti et al., 2010; Loureiro et al., 2010). Some of them (e.g. UK, Netherlands, Wallonia, Flanders, Switzerland) were published also through publicly available internet resources. Others, like the atlas of Sweden, were published exclusively on the internet. This wealth of novel data claims for an update of the herpetofaunal distribution data also at the European level, to quantify Europe-wide the improvement in knowledge since the previous Atlas, as well as a first step towards tracking potential changes in the distribution of the European herpetofauna in the context of global change.

Novel technologies for mapping species distributions currently available, such as newly developed Geographic Information Systems (Longley et al., 2010) and their extensions, offer the possibility of establishing extensive databases of distribution records, with associated metadata such as voucher specimen lists or photos. Citizen-science online tools allow contributors entering their observations, and directly link them to analysis tools such as spatial modelling or the production of customised maps. The current Mapping Committee of the SEH (established in 2006), together with the SEH Council and some associated fellows, has acknowledged that distribution atlases should be conceived as dynamic tools, implemented in a way that allows for continuous updates, extension changes, and customised data extraction while respecting the copyright that particular organisations or individuals might hold on parts of the underlying data. The goal is to establish a Spatial Data Infrastructure, a system of geographically distributed systems, where the original data remain on the servers controlled by national or regional herpetological societies, and through an online network it is possible to make data queries via the SEH portal (Sillero et al., 2014; see http://na2re.ismai.pt). For countries that do not have national databases, the SEH works on establishing a connected database linked to an internet portal for data collection.

A dynamic online atlas of European amphibians and reptiles based on an underlying distributed database of distribution records represents a major logistic challenge and is time-consuming. However, considering the current conservation crisis faced by many European amphibians and reptiles (Cox, Chanson and Stuart, 2006), it is an urgent task to make updated distributional information on these organisms available. The species distribution maps of the 1997 European Atlas (Gasc et al., 1997) have never been made available in GIS format. However useful and original at the time, they are now outdated due to the considerable accumulation of new distribution data, and especially because of the taxonomic progress that resulted in multiple changes of genus-level classification, and a large number of new species descriptions (Speybroeck, Beukema and Crochet, 2010; Vences et al., 2013). This new taxonomy resulted in many species being split into multiple entities for which the exact distribution limits are poorly known.

The goal of the present study is to provoke and facilitate filling of these gaps by making updated distribution maps for the European herpetofauna available. For this purpose, we have compiled information from a large number of published and partly unpublished mapping efforts at a variety of spatial scales and transformed those data into a 50 × 50 km UTM grid, similar to the one used for the 1997 European Atlas. Based on this new compilation of maps, all of which are made available (see online Supplementary Atlas S1-S5 online), we here (1) identify the major spatial and taxonomic gaps in the currently available knowledge in order to identify future research priorities, and (2) analyse patterns of species richness, endemism and main distribution types (i.e. groups of species with similar distribution patterns) for European amphibians and reptiles.

Materials and methods

Study area

This compilation included almost the same area as the 1997 European Atlas (Gasc et al., 1997). We used the limits for Europe (see Supplementary fig. S1 online) provided by Geocommons (http://geocommons.com/overlays/76975). The geographical limits of the previous SEH 1997 European atlas were those defined by Mertens and Wermuth (1960), covering parts or the whole of 45 countries. Partial territories included were: north-western tip of Turkey (European Turkey), territories in the Russian Federation west of the Urals, north-eastern tip of Azerbaijan, north-western tip of Kazakhstan, Greece minus the Sporades Islands. However, the Geocommons limits do not include parts of Azerbaijan and Kazakhstan, while the Ural limits are defined more precisely. These limits for Europe are widely accepted by many geographical atlases (e.g. Cheers, 2005).

Taxa

For historical consistency and to facilitate reading, in this paper we use the traditional term ‘reptiles’ for the paraphyletic group including the vertebrate orders Squamata, Testudines, Crocodylia, and Rhynchocephalia, i.e. Sauropsida excluding birds (of which only Squamata and Testudines are represented in Europe’s extant fauna). The species-level taxa considered in this compilation were determined by the SEH, using Speybroeck, Beukema and Crochet (2010) as starting point (see Supplementary Text S1 online). In numerous cases, although the species status of two or more related taxa is undisputed, we were unable to assign all available records to a species. This was either because the original databases had been compiled following an outdated taxonomy, or because many records could not be identified up to species level in the field (such as for instance, Triturus marmoratus and T. pygmaeus in the Iberian Peninsula). In these cases, we merged the respective species into a single entry in our database, which therefore in several cases represents a simplification of current taxonomy.

The sampling effort was obviously not homogeneous across the whole study area. Some countries have a very good knowledge on the ranges of their species while others have large gaps of chorological information. Although the present compilation is represented at a rather coarse scale (50 × 50 km grid), gaps in the species distributions are still observable. Similarly, not all national and regional data sets are fully consistent in their treatment of marine and introduced species. Where available, our compilation includes terrestrial as well as marine taxa (i.e. marine turtles). Besides native species and populations, a number of national data sets also included introductions, i.e. introduced species from outside Europe as well as introduced populations of European species occurring outside their natural range. In this case our compilation is not fully consistent. For marine turtles, some countries included records on sightings (on coast and ocean) and reproduction places (i.e. Portugal and Spain), while other countries only included reproduction places (i.e. Italy and Balkan countries). In general, we did not include single records of escaped exotic species where there was no indication of naturalised populations. For non exotics, we considered as introduced those cases where the origin of the introduction is well known and can be traced back into recent history, such as the populations of Discoglossus pictus in southern France and in Spain (Catalonia), but not those cases where ancient introductions are suspected (e.g. various species on Mediterranean islands). In this sense, much of the actual herpetofaunal composition in the Mediterranean is probably related to or at least influenced by human activities (Corti et al., 1999).

Database compilation

Our goal in compiling updated distribution maps for the European fauna was to cover as many European countries as possible with national atlas data or new personal records. The species data included in these updated maps were obtained from different data sources, namely (1) published (in books or websites) or on-going national atlases, (2) personal data kindly provided to the SEH, (3) the 1997 European Atlas, and (4) the Global Information Facility (GBIF: www.gbif.org). Because the GBIF data originate from many different data sources and contain numerous errors and discrepancies, we tried to minimise their use as explained below. However, a few of the national atlas data were directly available only from GBIF (e.g. Denmark and Norway) and in these cases, the data were labelled as National Atlas Data rather than as GBIF data. Some countries provided databases used in already published atlases (whole database with temporal data series: e.g. Spain and Portugal; simplified database: e.g. The Netherlands) or before publishing as an atlas (e.g. Slovenia and France). For other countries, we digitised the data from published books (e.g. Hungary). We also included large unpublished databases for several countries compiled by some co-authors of this study (e.g. S.L. Kuzmin, P. de Pous). In the case of territories of former Yugoslavia, J. Crnobrnja Isailović and collaborators provided some of the original data used in the 1997 European Atlas. National atlases and personal databases were subsequently merged in one database, which in the following will be referred to as COUNTRIES. A second database, hereafter named SEH/GBIF database, contained the data of the 1997 European Atlas and GBIF, but only for those countries for which no national atlas data were available. For the final compilation, the same exclusion strategy was also employed at the level of single UTM squares. Whenever a record from the COUNTRIES database was available for a UTM grid (only in personal databases: e.g. S.L. Kuzmin’s personal database) we used that one rather than the duplicate record from the SEH/GBIF database. This process was performed using spatial queries in ArcGIS 9.3.

Many original databases contained erroneous records. The databases were therefore reviewed and validated by members of the SEH Council and its Mapping Committee in various rounds. Erroneous records were excluded from the two main databases (COUNTRIES and SEH/GBIF) and stored in a different file. During this revision of the point locality data in the COUNTRIES and SEH/GBIF database, we furthermore flagged introduced species and species locations, and these were transferred to a third database hereafter called INTRODUCED. As such, we never deleted a record: keeping all erroneous records rather than simply deleting them allowed tracking validation errors and makes our decisions verifiable. Introduction records were defined using our current knowledge, which is not homogeneous, thus bias may be present for some species and regions.

The three databases were composed by point records. The numerous data (table 1; 30 databases) have been received in multiple digital formats, with disparate information and in different spatial resolutions (ranging from point centroids of 50 × 50 km UTM grid cells to very precise GPS point locality records). Therefore, the databases were homogenised, deleting all other information except species names, coordinates, and data source, and projected to the same coordinate system (WGS84).

Table 1.

List of databases used in this atlas compilation. Resolution, records, and sources refer to data obtained and used for the compilation of the European atlas. References to published atlases are mentioned. Some of these databases included more than one country (e.g. S.L. Kuzmin). See table 2 for number of records per country.

Table 1.

Map production

As an atlas is usually the representation of the species’ distributions by uniform units (Sillero, Celaya and Martín-Alfageme, 2005; Loureiro and Sillero, 2010), record points were transformed into a grid. We used the official UTM grid of 50 × 50 km, that it is freely available from the European Environment Agency (http://www.eea.europa.eu/). This grid is based on the one used for the European Atlas of Flora, the first biological distribution atlas for Europe (Jalas and Suonuinen, 1972). It includes 4524 land squares. Therefore, each point database (COUNTRIES, SEH/GBIF, and INTRODUCED) was transformed to a grid file, by spatially overlapping with the 50 × 50 km UTM grid. This transformation from the point databases (e.g. GPS points, as well as centroids of grids of 1 × 1 km, 4 × 4 km, 5 × 5 km, 10 × 10 km, and 50 × 50 km squares) to a grid database was performed by a set of GIS scripts for ArcGIS 9.3 (see Supplementary table S1 online) in which for each species, each grid was assigned 0 for absence or 1 for presence.

Figure 1.
Figure 1.

Example of species distribution map (Ichthyosaura alpestris) showing, in different colours, records corresponding to the COUNTRIES (red), SEH/GBIF (green) and INTRODUCED (purple) databases used in this study. Brown colours represent higher elevations. We used the official UTM grid of 50 × 50 km from the European Environmental Agency (www.eea.europa.eu/). COUNTRIES database included data from published or on-going national atlases, and from personal data kindly provided to the SEH. SEH/GBIF included data from the 1997 European Atlas and the Global Information Facility (GBIF: www.gbif.org). We only included data from SEH/GBIF when data from COUNTRIES database were not available. Datasets for introduced species were not available in all countries.

Citation: Amphibia-Reptilia 35, 1 (2014) ; 10.1163/15685381-00002935

The species maps (see example in fig. 1; all maps are provided online in Supplementary Atlases S1 and S2, and the corresponding GIS files in Supplementary Atlases S3 and S4; species codes are provided in Supplementary Atlas S5) were created automatically by overlapping the three grid files (COUNTRIES, SEH/GBIF, and INTRODUCED), using a script written in the R language (R 2.15, R Development Core Team, 2012). The script (included online in Supplementary Text S2) looked sequentially for each species in the three grids, representing them with different colours. The resulting maps were exported to images in .jpg format. Species richness maps for amphibians and reptiles were calculated by the sum of all species present in each grid cell. We then compared species richness maps with those based entirely on the original data of the 1997 European Atlas, and for each grid cell we subtracted the old from the new number of species occurring therein. The resulting valu