DOI: 10.5061/dryad.xsj3tx9dh
title: Understanding parapatry: How do environment and competitive interactions shape Iberian vipers’ distributions?

description: Aim: To assess if the parapatry of the three viper species present in the
 Iberian Peninsula is mainly caused by environmental conditions, historical
 events, interspecific competition among them, or a combination of these
 factors. Location: The Iberian Peninsula Taxon: Vipera aspis, V. latastei,
 and V. seoanei. Methods: We applied the concept of favourability of
 occurrence to produce commensurate distribution units unaffected by the
 prevalence of different species in the Iberian Peninsula. We compared the
 favourability of each species individually with the favourability of
 occurrence of more than one species co-occurring in their overlapping
 ranges, and identified the areas in which sympatric coexistence,
 environmental segregation, and competitive exclusion are predicted to
 occur. Results: The main driver of the parapatric pattern was competitive
 exclusion, which was mediated by gradual changes in the environmental
 conditions favouring each species. The para-Mediterranean V. aspis
 presented fragmented favourable areas outside its range that seemed to be
 unoccupied due to competitive exclusion by the other vipers. The
 Mediterranean V. latastei appeared to be limited by competition with the
 other viper species and by the environment in northwestern Iberia. V.
 seoanei prevented the other two species becoming established in the
 north-western quarter of the Iberian Peninsula due to its better adaption
 to the humid conditions in this region. Some areas of sustainable
 coexistence were detected, mainly in the upper reaches of the River Ebro.
 Main conclusions: Each species is better adapted to particular conditions.
 However, the existence of ecotones forces them to occur sympatrically and
 compete for resources. The parapatric pattern is a result of the
 evolutionary history of the species and of strong competitive interactions
 between them, which form ‘competitive-exclusion barriers’. However, these
 barriers are environmentally dependent, so changes in the environment
 could rapidly affect the limits of the species distribution.
description: The
 Iberian distributions of the three vipers were obtained from the
 distribution atlases of Spain (Pleguezuelos, Márquez, & Lizana,
 2002) and Portugal (Loureiro <i>et al.</i> 2008). This
 information was digitized and supplemented with new digitized data for
 Spain provided by the Asociación Herpetológica Española (Spanish
 Herpetological Association), recently published data (Martínez-Freiría et
 al., 2015, 2020), and unpublished data that have recently been collected.
 Species distribution data were latticed using UTM 10×10-km grid cells as
 operational geographic units.  
 References: Asociación Herpetológica Española: http://siare.herpetologica.es/ Loureiro, A., Ferrand de Almeida, N., Carretero, M. A., & Paulo, O. S. (2008). <i>Atlas dos Anfíbios e Répteis de Portugal</i>. Lisboa: Instituto da Conservação da Natureza e da Biodiversidade. Martínez-Freiría, F., Velo-Antón, G., & Brito, J. C. (2015). Trapped by climate: Interglacial refuge and recent population expansion in the endemic Iberian adder <i> Vipera seoanei </i>. <i>Diversity and Distributions</i>, <i>21</i>(3), 331–344. https://doi.org/10.1111/ddi.12265 Martínez-Freiría, F., Freitas, I., Zuffi, M. A. L., Golay, P., Ursenbacher, S., & Velo-Antón, G. (2020). Climatic refugia boosted allopatric diversification in Western Mediterranean vipers. <i>Journal of Biogeography</i>, <i>47</i>, 1698–1713. https://doi.org/10.1111/jbi.13861 Pleguezuelos, J. M., Márquez, R., & Lizana, M. (2002). <i>Atlas y Libro Rojo de los Anfibios y Reptiles de España</i>. Madrid: Dirección General de Conservación de la Naturaleza-Asociación Herpetologica Española.
description: These data are the presence/absence matrix used to modelled the
 three species distribution in a UTM 10x10 km grid cell shapefile (also
 included). <em>Vipera_spp.csv</em> contains the Iberian vipers
 distribution (in a CSV format using ";" as separator) and the
 rest of the documents <em>utm10PI.</em>xxx (<em>.CPG,
 .dbf, .prj, .sbn, .sbx, . shp, .shp.xml, .shx</em>) are the archives
 to link the distribution with the Iberian Peninsula shapefile . It is
 neccessary a GIS software to use this dataset.
 CODES:
 <strong>IBCUADR_ID</strong>: Identificator of the
 cell in the UTM grid cell of the Iberian Peninsula, used to link the
 species presence/absence matrix to the Iberian shapefile.
 <strong>V_aspis</strong>: cells with presence (1) or
 absences (0) of <em>Vipera aspis.</em>
 <strong>V_latastei</strong>: cells with presence (1)
 or absences (0) of <em>Vipera latastei.</em>
 <strong>V_seoanei</strong>: cells with presence (1)
 or absences (0) of <em>Vipera seoanei.</em>