| Abstract |
The complex geological history of the Balkan Peninsula and especially of the Hellenic area (multiple geological events of land connections) during the late Tertiary have likely contributed to the diversification and distribution of many terrestrial animals. Located at the margin of the Eurasian and African plates, this area has experienced tremendous geological alterations since the late Tertiary. Connections offered the opportunities for biological dispersal, while submergence of land bridges brought about distributive isolation among related taxa. If this was a major element influencing the formation of the rich fauna of the Hellenic area, then the phylogenetic relationships of terrestrial taxa should reflect these paleogeographic events. Compared with what is known for the geological history of this region, the impact of those geological events on the historical biogeography of terrestrial animals is less well understood. The reconstruction of phylogenies is of primary importance in the understating of the dynamic patterns of evolution, i.e. the biogeography of a group and the bases of its biological diversity at any level. Although the phylogeny of the genus Podarcis has been the subject of much discussion the relationships among the species are still unclear. Because morphology is so uniform, it provides few characters for phylogenetic analysis, and these tend to be conflicting. Various karyological, immunological and protein electrophoretic studies have been made, but these usually involve only a minority of species, and results from different species combinations are equivocal. Wall lizards of the genus Podarcis (Sauria, Lacertidae) comprises 17-18 currently recognized species in southern Europe, where they are the predominant reptile group. The taxonomy of Podarcis is complex and unstable. Based on DNA sequence data the species of Podarcis falls into four main groups that have substantial geographic coherence (Western Island group, South western group, Italian group and Balkan group). The Balkan species are divided in two subgroups: the subgroup of P. taurica (P. taurica, P. milensis, P. gaigeae and perhaps P. melisellensis), and the subgroup of P. erhardii (P. erhardii and P. peloponnesiaca). We addressed the question of phylogenetic relations among the species of Podarcis encountered in Balkan Peninsula, as they can be inferred from partial mtDNA (cyt b and 16S) and nuclear (c-mos) sequences. Our data support the monophyly of Podarcis and suggest that there are three phylogenetic clades: the clade of P. taurica (P. taurica, P. gaigeae, P. milensis, and P. melisellensis); the clade of P. erhardii (P. erhardii and P. peloponnesiaca) and the clade of P. muralis (P. muralis and P. sicula). The phylogenetic affiliations produced from the molecular data do not agree with the species and especially subspecies groupings predicted from the morphological classification of the populations sampled. By examining intraspecific variability we have found that extant populations of P. erhardii are paraphyletic. The high level of genetic differentiation observed in the mtDNA data between the P. erhardii populations from the Crete and Pori islands and the rest of P. erhardii samples from Cyclades and continental Greece and its phylogenetic position raises questions regarding the inclusion of those populations (Crete and Pori) within P. erhardii. Since, based on morphology, P. peloponnesiaca is a well defined species found in sympatry with P. e. livadhiaca and accepted today as such, then Podarcis from Crete and Pori would also need to be raised to specific rank to avoid the paraphyly of P. erhardii. However, although the differentiation of populations from Crete and Pori islands is clear, we suggest the use of PhyloCode in order to avoid taxonomic confusion at least until further research mainly on morphology becomes available. Thus, for the time being, we refer to wall lizards of Crete and Pori P. erhardii*. With regard to morphological subspecies of P. taurica, P. gaigeae and P. erhardii, it is clear that they do not represent monophyletic units and should be re-evaluated in the light of new evidence. The topology of the phylogenetic trees produced and the genetic distances among the clades of the Podarcis may describe a biogeographic hypothesis for these species in the Balkan area. The pattern of the distribution of the proposed taxa is congruent with existing paleogeographic evidence, as inferred by the application of a molecular clock, which supports the view that DNA sequences may be a useful tool for the study of paleogeography. The data analyzed, stress the need for a reconsideration of the evolutionary history of Balkan Podarcis species and help overcome difficulties that classical taxonomy has encountered at both the species and subspecies level. As a whole, the examination of mtDNA lineages in the lizards of genus Podarcis may contribute substantially to the refining of its taxonomic status. Phylogenetic information can now be added to the knowledge of their morphology and distribution, producing a more accurate taxonomy for this group. Our results also confirm that the molecular information in conjunction with geological data can be used to resolve questions about the paleogeography of a region or on the phylogeography of a species.
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| Subject |
Μοριακή φυλογένεση, μιτοχονδριακοί δείκτες, πυρηνικοί δείκτες, μοριακό ρολόϊ, Podarcis, φυλογεωγραφία, Ελλάδα, molecular phylogeny, mtDNA and nuclear markers, molecular clock, phylogeography, Greece |
Διερεύνηση των φυλογενετικών διεργασιών στις σαύρες του γένους Podarcis (Sauria: Lacertidae) του ελληνικού χώρου
