Morfološka varijabilnost i distribucija roda Theodoxus Montfort, 1810 (Neritomorpha, Gastropoda) u centralnom delu Balkanskog poluostrva i na južnom obodu Panonske nizije
Morphological variability and distribution of Theodoxus Montfort, 1810 (Neritomorpha, Gastropoda) in the central Balkan and southern edge of Pannonian plain
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The study includes a large number of data collected on the field, as well as the literature data. The spatial distribution and relationships between species are investigated. The spread and estabished dominance of T. fluviatilis in large lowland rivers, and much wider distribution of species T. danubialis i T. transversalis in the past were noted. Studied rivers Una, Sana and Vrbas are noted as potential corridors for the spread of T. fluviatilis, and connecting its Pannonian and Dalmatian range of distribution. It schould be mentioned that some of this species previous findings, apart of its typical habitats (potamon rivers) schould be rechecked. Distribution of T. transversalis, suffered the biggest change, resulting in a drastic reduction in its range. In the past, there have been records from several sites on the Danube, from Novi Sad through the Iron Gate to the mouth of the Timok River. Furthermore, reports were from other rivers ae well (the Sava River, the Moravica River). Despiteliterature data, the findings of this rare species in some localities in the Danube River suggests that it is still present but very rare. The site on which it is found (Stari Slankamen), could acts as one of the few remaining refugia for this rare species in the Danube. Findings from the Tisa River (Martonoš) and the Crni Timok River (Zaječar), schould be noted also. The analyses of its recent distribution showed that the Velika Morava River – Južna Morava River – Nišava River river system is the main refuga for the species. Results of preformed analysis have confirmed the general preferences of the species regarding the river type. Species T. danubialis i T. transversalis are the most present in river type 2 (large rivers outside of the Pannonian basin), while T. fluviatilis is dominant in river type 1 (large lowland rivers). Regarding its relation to water chemistry it has been showed that the most important of studied physico-chemical parameters on Theodoxus community were oxygen content, orthophosphates, ammona and water temperature. Multivariate analyzes indicate increased tolerance of T. fluviatilis to the low oxygen content and higher water temperature, as well as for increased ammona concentrations. Unlike the other two species are less tolerante to this conditions, especially T. danubialis. It is somewhat interesting that the rarest species T. transversalis has increased tolerance to organic nutrients (orthophosphates and nitrates)...
Keywords:Theodoxus; Interspecific variability; Intarspecific variability; Balkan; Tradicional morphometry; Morphometic indices; Multivariate statistics
Source:University of Belgrade, Faculty of Biology, 2014, 1-124