Friday, July 1, 2016

[Herpetology • 2016] Vipera walser • A New Vertebrate for Europe: The Discovery of A Range-restricted Relict Viper in the western Italian Alps

Vipera walser
Ghielmi, Menegon, Marsden, Laddaga & Ursenbacher, 2016

We describe Vipera walser, a new viper species from the north-western Italian Alps. Despite an overall morphological resemblance with Vipera berus, the new species is remarkably distinct genetically from both V. berus and other vipers occurring in western Europe and shows closer affinities to species occurring only in the Caucasus. Morphologically, the new species appear to be more similar to V. berus than to its closest relatives occurring in the Caucasus, but can be readily distinguished in most cases by a combination of meristic features as confirmed by discriminant analysis. The extant population shows a very low genetic variability measured with mitochondrial markers, suggesting that the taxon has suffered a serious population reduction/bottleneck in the past. The species is extremely range-restricted (less than 500 km2) and occurs only in two disjunct sites within the high rainfall valleys of the Alps north of Biella. This new species should be classified as globally ‘endangered’ due to its small and fragmented range, and an inferred population decline. The main near-future threats to the species are habitat changes associated with reduced grazing, along with persecution and collecting.

Keywords: Vipers; Vipera berusVipera walser; reptile conservation; new species; bPTP species delimitation model; Alps; biogeography; climate change

Vipera walser
Ghielmi, Menegon, Marsden, Laddaga & Ursenbacher, 2016 

Figure 6. Pattern variation in adult male (left) and adult female (right) of Vipera walser sp. nov.

Figure 7. Variation in head scalation in adult female (upper four photographs) and adult male (lower four photographs) of Vipera walser sp. nov.
 DOI: 10.1111/jzs.12138  


Vipera walser
Ghielmi, Menegon, Marsden, Laddaga & Ursenbacher sp. nov. 

Holotype: Adult female: MSNG34485, collected in S. Giovanni d'Andorno, on the road to Oropa in the Biella prealps, at about 1300 m a.s.l. by A. Rosazza in the summer of 1930 (Fig. 5).

Paratypes: One adult male: MSNG33638M collected at Monte Rosso del Croso, on 30 August 1933. One juvenile male: MSNG33637B and one subadult male: MSNG30818C collected at Alpe Finestre by Felice Capra, respectively, on 28 July 1930 and 15 August 1928. One adult female: MSNG30818A, one subadult female: MSNG30818B, and two juvenile females: MSNG33637C and MSNG33637D collected by Felice Capra at Alpe Finestre between August 1928 and August 1939. One juvenile female: MSNG30286 collected by F. Capra at Monte Rosso del Croso on 12 September 1934; one adult female MSNG33637A collected by F. Capra at Alpe le Piane on 5 August 1937; one adult female MSNG41663 collected by A. Margiocco at Piedicavallo in September 1967.

Type locality: San Giovanni d'Andorno, strada per Oropa at 1300 m a.s.l. in the Alps north of town of Biella, a subrange of the Pennine Alps, north-western Italy.

Differential diagnosis: Vipera walser sp. nov. is generally similar to the species of the subgenus Pelias and can be confused with V. berus, which co-occurs on the Alps in allopatry (Fig. 6, Table 2). The species differs in a generalized higher count of cephalic scales, in particular the ones listed below (V. berus in parentheses): higher number of crown scales: 7–30, mean 17.4 (versus 4–22, mean 13.0); loreals: 4–15, mean 9.36 (versus 2–12, mean 6.72); and, to a lesser extent, perioculars: 16–23, mean 19.8 (versus 13–23, mean 18.4) (see Table 2). V. walser, in contrast to V. berus, also shows a marked tendency towards fragmentation of the cephalic large shields: the parietal scales are often completely broken down into several smaller scales: 2–14, mean 6.3 (versus 2–10, mean 2.4; see also Fig. 7). Less commonly, also the frontal scale is fragmented into smaller scales. Some individuals exhibit a dorsum of the head covered in small, irregular scales, like in V. aspis. V. walser has between 1.5 and 2 rows of subocular scales on both sides of the head in 85% of the analysed specimens (V. berus has typically one row of suboculars, with the exception of some populations in the southern Alps). The dorsal zigzag is often broken down into separate bars as in Vipera aspis (Linnaeus, 1758) or Vipera berus bosniensis (see Fig. 6). Despite the lack of a strictly diagnostic morphological character, V. walser can be readily distinguished from populations of V. berus from Central and northern Europe by a combination of several characters (e.g. the number of subocular scales, fragmentation of parietals and number of apicals). Identification based solely on observation of external morphology is less obvious if individuals of V. berus from southern Alps are considered. Despite this, discriminant analysis correctly identified individuals to species in 94% of females and 88% of males, based on a set of analysed characters (see Figs 2 and 3). The mean p-distance, based on a combined dataset of about 3000 base pairs of mitochondrial genes, between V. berus and V. walser is 5.36%. Based on our current knowledge of its distribution, Vipera walser is restricted to the Alps north of town of Biella, a subrange of the Pennine Alps, west of the river Ticino, north-western Italy (Fig. 8).

Etymology: Vipera walser sp. nov. is named after, and dedicated to, the Walser people with whom it shares an extraordinary beautiful and wild area of the south-western Alps.

Figure 8. Currently known extent of occurrence of Vipera walser sp. nov. (in blue) and V. berus (in red) in north western Italy
 DOI: 10.1111/jzs.12138  

Figure 6. Pattern variation in adult male (left) and adult female (right) of Vipera walser sp. nov.
Figure 9. Habitat of Vipera walser sp. nov; Valle Mastallone at 2,070 m (left) and Valle Strona at about 1,800 m (right)

The present study described and named a new viper species, V. walser, which shows strong genetic divergence and clear morphological differentiation from all other known European viper species. The new taxon occurs in a restricted area of the south-western Italian Alps and shows close affinities with the Caucasian species V. dinniki, V. darevskii and V. kaznakovi, opening unexpected and interesting biogeographic scenarios. The very small extent of occurrence of the new species implies a particularly high threat level, and thus conservation managements should be developed. The protection of its habitat, the limitation of the forest regrowth, but also the evaluation of its likely future distribution given climatic changes (for the long term) or struggle against culling (short term) are key elements to investigate. Involvement of local authorities, foundations and other stakeholders will be crucial in realizing effective protection of this species.

Samuele Ghielmi, Michele Menegon, Stuart J. Marsden, Lorenzo Laddaga and Sylvain Ursenbacher. 2016. A New Vertebrate for Europe: The Discovery of A Range-restricted Relict Viper in the western Italian Alps. Journal of Zoological Systematics and Evolutionary Research.  54(3); 161–173.  DOI: 10.1111/jzs.12138