The use of geostatistics and GIS for evolutionary history studies: the case of the nose-horned viper (Vipera ammodytes) in the Balkan Peninsula

Abstract

Geostatistics and geographical information system (GIS) procedures are novel techniques helpful for the identification of environmental correlates sustaining contact zones among subspecies or closely related species. In this paper, we tried to infer evolutionary scenarios for Vipera ammodytes across the European part of its distribution area using geostatistics and ecological niche-based models, hence trying to solve several biogeographical questions that remained unclear after the application of classical morphological tools and genetic analyses. Eleven morphological traits from 871 vipers were analysed with geostatistics and ecological niche-based modelling. Interpolation by kriging was used to generate surfaces of morphological variation, which were combined with spatial principal components analysis (SPCA). SPCA maps were used to test putative morphological differentiated groups with discriminant function analysis (DFA). Maximum entropy modelling and seven environmental variables were used to identify factors limiting the distribution of groups and areas for the potential occurrence of such groups. Three patterns of morphological variation were observed: a north-west/south-west cline, transition zones with steep clines of variation in a west-east arc, and particular character traits that disturbed the general cline. SPCA identified between three and nine putative population groups, of which three were supported by DFA. Areas of potential occurrence of these groups were coherent with the range of the three subspecies of V. ammodytes currently recognized. The distribution of all subspecies was mostly related to precipitation in the driest month. Areas of probable sympatry between subspecies are generally small and restricted. The main patterns of geographic variation of morphological characters for V. ammodytes were similar to the patterns obtained for Vipera latastei and Vipera monticola; the same environmental factors limit the distribution of differentiated groups of vipers in the Balkans and the Iberian Peninsula. The influence of humidity on the variation of morphological traits in spatially separated viper taxa from the two European peninsulas coincides with their phylogenetic relatedness. Geostatistics and GIS procedures were successful in the identification of environmental correlates sustaining contact zones among V. ammodytes subspecies in the Balkans. The same techniques should be applied for studying other parapatric forms and refugia regions.

Biogeography and conservation of viperids from North-West Africa: An application of ecological niche-based models and GIS

“…The relation between occurrence of vipers and EGVs was determined by the visual examination of response curves profiles from univariate models . Similar profiles between two vipers for a given EGV were taken as an indication of parallel relationships between the occurrence of these species and the range of variation of the EGV Martínez-Freiría et al, 2008;Tomovi c et al, 2010). This indicates also the possible occurrence of sympatry and eventual competition within the range of values of the EGV equally selected by both species.…”

“…This modelling technique requires only presence data as input, and consistently performed well in comparison to other methods (Elith et al, 2006), especially at low samples sizes (Hernandez et al, 2006;Wisz et al, 2008), and it has been used successfully in ecological niche-based modelling of viperid snakes (e.g. Brito et al, 2008;Escoriza et al, 2009;Martínez-Freiría et al, 2008;Tomovi c et al, 2010).…”

“…Three sets of environmental factors or ecogeographical variables (hereafter EGV) were selected for the ecological models according to their meaning to the ecology and distribution of viperid snakes Escoriza et al, 2009;Martínez-Freiría et al, 2008;Santos et al, 2006;Tomovi c et al, 2010). These sets included one topographical grid (USGS, 2006) that was used to derive the variable Slope, with the "Slope" function of ArcGIS; seven climate grids (Hijmans et al, 2005); and a land-cover grid from the years 2004e2006 (Bicheron et al, 2008).…”

“…Distinct niche selection in contact zones has been suggested to be related to local parapatric ranges in vipers (Brito and Crespo, 2002;Brito et al, 2008;Martínez-Freiría et al, 2008;Tomovi c et al, 2010), and this seems to be the case of both Cerastes, since C. cerastes occurs mostly in rocky habitats while C. vipera selects sandy areas Trape and Mané, 2006). Nevertheless, the contribution of climatic and other habitat factors to shape species ranges remains largely unknown.…”

Integrating classical and spatial multivariate analyses for assessing morphological variability in the endemic Iberian viper Vipera seoanei

“…, ; Tomović et al. ). On the one hand, the ectothermic physiology makes vipers highly dependent on climatic factors (e.g.…”