The unknown reptiles of Slovenia

If you believe that the reptiles and amphibian species of central Europe are well known, think again. Here, I present a tentative species list, as a basis for discussion. 
 
 
How many species of amphibians and reptiles occur in Slovenia?
The easy answer is 19 amphibian species and 23 reptile species. This is including a non-breeding species (loggerhead turtle) and a recent discovery (Danube crested newt – which naturally occurs near the Hungarian border). Also, it includes the cat-snake, of which there are no recent observations: it may be locally extinct.
 
This number does not include Balkan whip snake: there is a single convincing observation, documented with a photograph, in a habitat which looks suitable. However, despite intensive searches, the species could not be found again, so there may not be a population present. It also does not include the scheltopusik, which is sometimes mentioned for southwestern Slovenia. The alleged locality (Panovec forest) has an entirely unsuitable habitat for the species and it is hard to believe that there would be a practically unrecorded population in this place, which is frequently visited by herpetologists. Gekko’s and tortoises occur nearby and are occasionally found in Slovenia, but there is no evidence that there is an established population here, so they are not on the list either. 
 
I also did not count alien species, of which two are established: red-eared slider terrapins and Balkan frogs; Pelophylax (ridibundus) kurtmuelleri. Like in other parts of the world, we also have our share of incidental escapes, releases and accidentally transported amphibians and reptiles: they are not on the list. 

This is the easy part, just a matter of deciding yes or no. Read on for the more interesting part … 

 

New research methods = more species

With every new research method, we discover more diversity in the natural world. This seems especially so with DNA research, but, differences which are discovered on basis of DNA are surprisingly often just a reason to publish morphological differences as well. And, field-workers are often well aware of these morphological differences, long before the DNA evidence gives a hint that we are looking at different species. So, which cases do we have in Slovenia? Here is a list, based on literature as well as personal gut feeling. 

Zootoca: all available evidence indicates that there are two full species of viviparous lizards in Slovenia. Z. vivipara and Z. carniolica. The latter differs because of its reproductive mode (egg-laying), ventral scale count, femoral pore count and ventral colouration in males. there is also evidence for reproductive isolation in a contact zone in Italy. 

Podarcis muralis: the coastal wall lizard subspecies nigromaculatus may well be a separate species: it differs in relative dimensions, ventral colour in males and dorsal colour of males. It is unclear if there is reproductive isolation, some introduced populations outside of its distribution may be hybridising with nominate wall lizards.

Lacerta viridis: for a long time it is known that there are two green lizard species in Slovenia, but now it appears that the western is an undescribed species rather than L. bilineata. In the Pannonian plain of hungary there may be an undescribed taxon as well: smaller, browner coloured than L. viridis and in appearance a bit sandlizard-like. Would this also occur in Slovenia?

Hierophis viridiflavus: could the eastern black form of the green whip snake be a distinct species? If so, it would just mean a name-change, since the nominate green subspecies is not found in Slovenia, just the black one is. 

Proteus anguinus: genetic evidence indicates that the cave-dwelling olm consists of several full species. One of these is the black olm, which has moderately well developed eyes (Proteus parkelj). However, there are also several “white olms” … 

Lissotriton vulgaris: In Slovenia, there are two subspecies of the smooth newt, which are are highly distinct, especially in the appearance of males in breeding season. I know that some research has been done on the distribution and possible hybrid zone, but I don’t know the outcome. 

Bufo bufo: Slovenian common toads look pretty much like the French Bufo spinosus, but apparently they are not the same species. In general common toads in Europe may be a species complex which hides several good species. Who would be interested to sponsor a serious research project?

Hyla perrini: the Italian treefrog likely does not occur in Slovenia, but there is introgression in the border region. So, some of the genes of H. perrini may have found their way into the local Slovenian H. arborea populations.

 

And some hybrids: 

In Slovenia, there are several cases of naturally hybridising amphibian species. The best known is the case of green frogs, in which hybrids between pool- and marsh frog are often included in species lists under the name Pelophylax kl. esculentus. With a google search, you will find a lot of information about this highly interesting species complex, so I will not write too much here. 

Also, in Slovenia, there is a hybrid zone between yellow- and fire-bellied toads. And the recently discovered population of Danube crested newts appears to hybridise with Italian crested newts. 

 

So, how many species of amphibians and reptiles are there in Slovenia?

Well, that depends on how you count them. I made a list below and let’s see what future research brings for new insights!

Written by Paul Veenvliet on 16.12.2018

Turtles of Slovenia

Emys orbicularis orbicularis
Emys orbicularis hellenica
Trachemys scripta elegans (alien species, established)
Caretta caretta (non-breeding but regularly present)

Lizards of Slovenia

Zootoca vivipara
Zootoca carniolica
Lacerta agilis
Lacerta viridis
Lacerta cf. viridis (undescribed species)
Podarcis muralis
Podarcis (muralis) nigromaculatus
Podarcis melisellensis
Podarcis siculus (or, is it going to be P. campestris?)
Iberolacerta horvathi
Algyroides nigropunctatus
Anguis fragilis

Snakes of Slovenia

Natrix natrix (including striped colour variety, which is not a separate subspecies)
Natrix tesselata
Coronella austriaca
Zamenis longissimus
Elaphe quatuorlineata
Telescopus fallax (possibly locally extinct)
Hierophis (viridiflavus) carbonarius
Vipera berus (Alpine clade)
Vipera berus bosniensis
Vipera aspis
Vipera ammodytes

Salamanders and newts of Slovenia

Proteus anguinus
Proteus (anguinus) parkelj
Proteus cf. anguinus (undescribed species)
Salamandra salamandra
Salamandra atra
Lissotriton vulgaris vulgaris
Lissotriton vulgaris meridionalis
Mesotriton alpestris (should be Ichtyosaura alpestris, I know, but I don’t like that name: it’s a marine dinosaur!)
Triturus carnifex
Triturus dobrogicus

Frogs and toads of Slovenia

Bombina variegata
Bombina bombina
Bufo cf. bufo (undescribed species)
Bufotes viridis
Pelobates fuscus
Hyla arborea
Rana temporaria
Rana arvalis
Rana dalmatina
Rana latastei
Pelophylax lessonae
Pelophylax ridibundus
Pelophylax ridibundus kurtmuelleri (established alien species)

Hybrid amphibians and reptiles of Slovenia

Triturus carnifex x T. dobrogicus
Bombina variegata x B. bombina
Pelophylax kl. esculentus = P. lessonae x P. ridibundus
P. ridibundus kurtmuelleri x P. ridibundus ridibundus

There are incidental findings of hybrid vipers, Vipera spp.
Podarcis (muralis) nigromaculatus may hybridise with P. m. muralis in places where nigromaculatus is introduced

Emys orbicularis orbicularis has hybridised with introduced other subspecies

The alien Trachemys scripta elegans occasionally hybridises with T. s. scripta, which is also introduced. Such hybrids have also been in trade any may be released in the wild.

Unclear or unconfirmed

Testudo hermanni: no extant populations, but may have been present in the past
Dermochelys coriacea: possible vagrant, recorded elsewhere in the Adriatic sea

Tarentola mauretanica: may be present in the coastal cities
Hemidactylus turcicus: may be present in the coastal cities
Lacerta cf. viridis undescribed Pannonic taxon: if it is a distinct taxon, it may also occur in the Pannonian part of Slovenia
Pseodopus apodus: unlikely: the single record may refer to a transported or introduced specimen, or may be incorrect

Hierophis gemonensis: 1 observation, occurrence needs confirmation

Hyla perrini: present close to the Slovenian border in Italy

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