Abstract
Abstract. The Balkans is a biogeographically highly diverse region and a worldwide hotspot of endemic freshwater diversity. A substantial part of this diversity is attributed to well recognized and potential ancient lakes in its southwestern part. However, despite considerable research efforts, faunal relationships among those lakes are not well understood. Therefore, genetic information from native representatives of the mussel genus Dreissena is here used to test the biogeographical zonation of the southwestern Balkans, to relate demographic changes to environmental changes, to assess the degree of eco-insularity, to reconstruct their evolutionary history, and to explore the potential of native taxa for becoming invasive. Phylogeographical and population genetic analyses indicate that most studied populations belong to two native species: D. presbensis (including the distinct genetic subgroup from Lake Ohrid, "D. stankovici") and D. blanci. In addition, the first confirmed record of invasive D. polymorpha in the southwestern Balkan is presented. The distribution of native Dreissena spp. generally coincides with the biogeographical zonations previously suggested based on fish data. However, there is disagreement on the assignment of the ancient lakes in the area to respective biogeographical regions. The data for Lake Ohrid are not conclusive. A closer biogeographical connection to lakes of the Vardar region and possibly the northern Ionian region is, however, suggested for Lake Prespa. The reconstruction of the evolutionary history of Dreissena spp. suggests that populations underwent demographic and spatial expansions in the recent past. Expansions started around 320 000–300 000 years ago in "D. stankovici", 160 000–140 000 years ago in D. blanci, and 110 000–70 000 years ago in D. presbensis. These time frames are discussed within the context of available paleogeological data for lakes Ohrid and Prespa. It is suggested that regional environmental changes may have had pronounced effects on the population histories of native Dreissena spp., though the high buffer capacity of Lake Ohrid may have lessened these effects in "D. stankovici". In addition, local events influencing individual lakes had very likely considerable effects on the demographic histories of Dreissena spp. as well. The observed patterns of immigration and emigration in and out of ancient lakes may suggest that limited gene flow enabled the survival of few isolated subpopulations and that later on eco-insularity (selective advantages of locally adopted groups) may have prevented excessive hybridization and sympatry of closely related taxa. As for the potential invasiveness of native Dreissena spp., the inferred spatial expansions are not human-mediated and all taxa still appear to be restricted to their native ranges. A concern, however, is that today D. presbensis and D. blanci also occur in artificial water bodies, and that invasive D. polymorpha has reached the area.
Highlights
The Balkans, a mountainous area in southeastern Europe, have long been recognized as a worldwide hotspot of endemic freshwater biodiversity (Radoman, 1985; Banarescu, 1991; Griffiths et al, 2004; Strong et al, 2008)
Wilke et al.: Native Dreissena freshwater mussels in the Balkans the major European Pleistocene refugia (e.g. Denefle et al, 2000; Tzedakis, 2009; Lezine et al, 2010), (ii) its rich geological history, for example, the upheaval of various mountain ranges, the interplay of Tethys and Paratethys, and the former contact to Anatolia (Radoman, 1985; Banarescu, 1991), (iii) its various biogeographical zones (Banarescu, 2004), and (iv) its high diversity of freshwater habitats ranging from cold springs, glacial lakes and mountain streams to ephemeral rivers and extended lake systems, including a number of actual or potential ancient lakes
Sub-network I comprises all haplotypes of native Dreissena presbensis, including those of “D. stankovici”, sub-network II all haplotypes of native D. blanci, and sub-network III the single haplotype of invasive D. polymorpha (Fig. 2)
Summary
The Balkans, a mountainous area in southeastern Europe, have long been recognized as a worldwide hotspot of endemic freshwater biodiversity (Radoman, 1985; Banarescu, 1991; Griffiths et al, 2004; Strong et al, 2008). The southwestern Balkans arguably are home to all the ancient lakes in Europe, except for the Caspian Sea (Albrecht and Wilke, 2008; see Fig. 1). These lakes comprise ancient Lake Ohrid, situated in the Former Yugoslav Republic of Macedonia (from hereon called Macedonia) and the Republic of Albania (from hereon called Albania), as well as Lake Prespa (Macedonia, Greece, Albania). As ancient lakes have often existed continuously for hundred thousand or even millions of years, and as they can harbour a high degree of endemic faunal elements, they are popular systems for reconstructing faunal relationships and changes in species composition in space and time (e.g. Martens, 1997)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
