Abstract
The smooth snake Coronella austriaca is a widespread Palearctic colubrid species. The species has been the subject of several molecular and phylogeographic studies which highlighted the occurrence of distinct genetic lineages in different areas of the species distribution, but scarce cytogenetic data are currently available on the species. In this paper we present a molecular and karyological study performed with several banding, staining methods and NOR-FISH on samples of C. austriaca from different geographical areas (Italy and Greece) of the species distribution. The molecular and phylogenetic analysis unambiguously placed the studied samples in different clades with a clear geographical pattern. The karyotype of the two female samples studied was composed of 2n = 36 chromosomes with 16 macro- and 20 microchromosomes and a mix of plesiomorphic and derivate chromosome features. All macrochromosomes were biarmed with the exception of pair 5 that was telocentric. NORs were detected on a microchromosome pair. In both females, the pair 4 was heteromorphic (and completely heterochromatic after C-banding in the Italian female), representing the first report of a ZZ/ZW sex chromosome system with female heterogamety in C. austriaca. In addition, the W chromosome showed a different morphology between the two female studied (submetacentric and subtelocentric), highlighting the occurrence of a chromosomal diversification among distinct geographical areas of the species distribution and further supporting that the species contains different diverging evolutionary clades.
Highlights
The smooth snake Coronella austriaca Laurenti, 1768, is a small sized ovoviviparous colubrid with a widespread distribution across the western Palearctic (Strijbosch, 1997)
In its large distribution range, the species have a relatively uniform morphology and only two subspecies are currently recognised: C. a. acutirostris Malkmus, 1995, from the north-western Iberian Peninsula and the nominal subspecies C. a. austriaca which occupies the rest of the geographical range of the species
In this work we present the results of a karyological study performed on smooth snake samples belonging to different populations and geographical areas of the species distribution (Italy and Greece) using several standard staining and banding methods and molecular cytogenetics
Summary
The smooth snake Coronella austriaca Laurenti, 1768, is a small sized ovoviviparous colubrid with a widespread distribution across the western Palearctic (Strijbosch, 1997). Coronella austriaca is absent from European and Mediterranean islands, except for Southern England, Sicily, the Island of Elba and the Island of Krk (Engelmann, 1993; Strijbosch, 1997; 2006). In its large distribution range, the species have a relatively uniform morphology and only two subspecies are currently recognised: C. a. Acutirostris Malkmus, 1995, from the north-western Iberian Peninsula and the nominal subspecies C. a. Austriaca which occupies the rest of the geographical range of the species. Fitzingeri (Bonaparte, 1840) was formerly described from southern Italy and Sicily, but it has been recently synonymised with the nominal subspecies (Speybroeck et al, 2016). The species has been the object of several molecular and phylogeographic studies (Santos et al, 2008; Llorente et al, 2012; Galarza et al, 2015; Jablonsky, 2019) and rep-
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