ANNALES • Ser. hist. nat. • 11 • 2001 • Suplement - Abstracts
Interdisciplinary Workshop "Pattern and Process in Balkan Biodiversity", Koper, September 25-28 2001
DIVERSITY OF AMPHIBIANS AND REPTILES ON THE BALKAN PENINSULA
Georg DŽUKIČ
Institute for Biological Research "Siniša Stankovič", Belgrade, FR Yugoslavia
Miloš L. KALEZIČ
Institute for Biological Research "Siniša Stankovič", Belgrade, FR Yugoslavia and Institute of Zoology, Belgrade, FR Yugoslavia
The Balkan amphibians and reptiles are diversified in many respects. First of all, there is an enormous species- 
richness in the Balkan Peninsula. Approximately 100 species of these vertebrates live in this part of Europe, with also 
the realistic possibility of the existence of a number of morphologically cryptic taxa.
Secondly, batrachofauna (amphibians) and herpetofauna (reptiles) of this part of Europe has diverse bio- 
geographical origins and connections with other regions. Namely, the Balkans appear to have been centre of inten­
sive speciation within some taxa. There is evidence that new species emerged during Tertiary (mostly Miocene and 
Pliocene), whilst subspecies origin was confined to the Pleistocene. Furthermore, there were intense migrations of 
amphibians and reptiles from other zoogeographical areas via two main migration routes (the Pontic Bridge and 
mostly the Morava River Corridor). In the first place, there is a large front of contact with steppes to the east and 
northeast, whilst the Aegean Islands constituted a connection with the African and Asian fauna. In addition, in con­
trast to the Iberian and Apennine peninsulas, the Balkan Peninsula is not separated by a mountain barrier from the 
European mainland, and thus is widely connected with central Europe and therefore, the rest of continent. This has 
crucial importance for the European batracho- and herpetofauna, because it has been shown that central and north­
ern Europe were populated by expansions from a Balkan refugium in the Holocene. Also, some groups have with­
drawn from northern and mid European latitudes, some of them now being restricted to southern refugial areas.
On zoogeographical grounds, the Balkan Peninsula is also characterised by numerous discontinuities; i.e. the zoo- 
geographical map is very complex with elaborate subdivisions, as well as with a wealth of preglacial faunal elements. 
Also, this area is the strongest centre of reptile and amphibian endemnicity in Europe, with the more than 45 endemic 
species, and many relict taxa. Due to these facts, some parts of the Balkans, in particular the Adriatic triangle (broadly 
speaking Prokletije Mt. area), are recognised as being one of Europe's main biogenetic reserves. As these isolated 
populations are mostly at species' range limits, there are numerous cases of range shrinking in the Balkan area. Of all 
species living in Balkans, 53% have range limits there. Although most of these peripheral populations are not going to 
evolve into distinct entities, there is still an astonishing potential for further evolutionary diversification.
In terms of general biological phenomena, Balkan amphibians and reptiles usually have much more inter- and 
intrapopulation genetic variability (in terms of allelic variation and a number of distinct genomes) when compared 
with other European areas. Diverse types of hybridisation and intergradation zones, which are differently spatially 
orientated (N-S, NW-SE directions, vertical distribution), are common on the Balkan Peninsula. Interspecific and in­
traspecific heterochronic phenomena expressed as a retention of ancestral larval features by a reproductively mature 
adult descendent (paedomorphosis and paedogenesis, respectively) are common among Balkan tailed amphibians. 
Paedomorphosis characterises the only European real cryptobiont (Proteus anguinus), while the existence of alterna­
tive life-history pathways among individuals of the same population (paedogenesis) is extremely high in Balkan 
newts (Triturus), especially along the Dinaric Alps. Also, it seems that hybridogenesis occurs in a number of green 
frog complexes (Rana kleptons), more than elsewhere. Finally, as in other places in Europe, there are more repro­
ductive modes (oviparity vs. viviparity) within a single species (Lacerta vivipara).
In general, genesis of the present day diversities of the Balkan amphibians and reptiles was influenced by numer­
ous factors, e.g. habitat heterogeneity, topographic diversity (mostly influenced by Pleistocene glaciations), great 
variation in climate, differences in rates of immigration, evolutionary and ecological time, etc. It should be stressed 
that geological history and palaeogeography of the Balkan Peninsula has undergone complex perturbations, espe­
cially during the Tertiary. Also, there is a correspondence of zoogeographical boundaries with the distribution of 
deep lithospheric breakages (crustal megablocks), so that these geological events might profoundly effect the evolu­
tionary history at least of some Balkan amphibians (e.g. Triturus cristatus superspecies).
However, for a more comprehensive picture of Balkan amphibians and reptiles we still lack many relevant data 
on longstanding taxonomic problems, population structure, distributional characteristics of some taxa (size, shape, 
boundaries, overlaps and locations of geographic ranges), especially those which can be considered as a "zoo- 
geographic paradoxes" (occurrence of isolated populations in "unexpected places"). Also, historical biogeographical 
patterns remains almost unexplored thus far, including the phylogenetic relationships of species and, especially, 
taxon-area cladograms.
Key words: reptiles, amphibians, evolution, diversity, tectonics
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