Hybridization between a Euro‐Siberian (Vipera berus) and a Para‐Mediterranean viper (V. aspis) at their contact zone in western France

Abstract

Western European vipers are well‐defined species with parapatric distributions that reflect contrasting thermal niches and climatic adaptations. Contact zones are usually narrow, coincide with steep ecological gradients and are associated with clear habitat segregation. Natural hybridization has been demonstrated between several species but has not been detected in others. The cold‐adapted adder (V. berus, subgenus Pelias) is not known to hybridize with the warm‐adapted aspic viper (V. aspis subgenus Vipera). For over 12 years, we have monitored sympatric populations of V. berus and V. aspis in western France where the two species exhibit very similar life cycles. We tested for possible hybridization because individuals with intermediate morphological traits have been reported in the past and were recently detected in the study population. Our results demonstrate that hybridization actually occurs and is directional since it involves females V. aspis viper and male V. berus in all analyzed cases. We discuss our results in the frame of previous findings on contact zones to evaluate in which conditions hybridization may occur.

Genotyping validates photo‐identification by the head scale pattern in a large population of the European adder (Vipera berus)

“…We intentionally only show images of adult adders, to exclude aberrant scalation patterns that could lead to lower survival abilities during immature life stages. The two rightmost scalation patterns on the bottom row resemble those of hybrids between Vipera berus and V. aspis from western France (compare to drawings in Table of (Guiller et al., ))…”

“…Most remarkable was the fragmentation of the largest elements of the pileus, that is, the frontal and especially the parietal scales. In some of our adders, fragmentation of these shields was so pronounced that they resembled individuals from western France that were shown to be natural hybrids of V. berus and V. aspis (Guiller, Lourdais, & Ursenbacher, ). Such hybrids are, however, unlikely to occur in our area, as the nearest population of V. aspis is located at 240 km SE.…”

“…We intentionally only show images of adult adders, to exclude aberrant scalation patterns that could lead to lower survival abilities during immature life stages. The two rightmost scalation patterns on the bottom row resemble those of hybrids between Vipera berus and V. aspis from western France (compare to drawings inTable 1of(Guiller et al, 2016)) T A B L E 1 Summary statistics (first line: median (interquartile range), second line: range) of the number of head scales in distinct scale groups (seeFigure 2) in male (n = 1,678) and female (n = 1…”

Evaluating taxonomic inflation: towards evidence-based species delimitation in Eurasian vipers (Serpentes: Viperinae)

“…Yet, relying on mtDNA as the only source for phylogenetic inference could be problematic (see Ballard and Whitlock, 2004), and thus, the phylogenetic patterns retrieved here should be interpreted with some caution. The existence of local hybridization between highly differentiated species (e.g., Tarroso et al, 2014;Guiller, Lourdais and Ursenbacher, 2017) and the growing evidence for extensive gene flow in more recently differentiated taxa (Zinenko et al, 2015(Zinenko et al, , 2016 highlight the importance of nuDNA analyses. However, despite being commonly used in species delimitation studies, the sequenced nuDNA markers were too conserved to consistently differentiate between otherwise well supported species of Eurasian vipers.…”

Cytochrome b mitochondrial gene analysis-based phylogeography of a Sand lizard in the Crimea: ancient refugium at the peninsula, late expansion from the North, and first evidence of Lacerta agilis tauridica and L. a. exigua (Lacertidae: Sauria) hybridization

“…Дискриминантный анализ 2005; Zinenko 2004Zinenko , 2006. Напротив, признаки интрогрессии между видами прослеживаются на ограниченных участках с особыми условиями природной среды (Guiller et al 2016), хотя узость гибридной зоны может свидетельствовать и о недавнем контакте их ареалов (Ефимов и др. [Yefimov et al] 2008).…”