Comparative biocenological analysis of Gastropoda on the Macedonian part of Lake Ohrid and its watershed

Abstract

Lake Ohrid represents a refugial ecosystem which harbors a great number of endemic and relics living forms. Though the whole Lake’s fauna characterizes high biodiversity and endemism, this is most obvious in the class of Gastropoda. Unlike the Lake, the fauna of the adjacent waters fairly differs from the Lake’s fauna, i.e., it is poorer both in term of diversity and endemism. The main goal of our study was to perform comparative biocenological researches on the gastropod fauna from Lake Ohrid and the adjacent waters in the watershed of the Lake. Based on the results we have obtained, it could be clearly noted that different habitats are characterized with different qualitative composition of the gastropod fauna not only when compared the gastropod settlement between the Lake and its surrounding waters, but also in the Lake for itself. Total of 50 species of gastropods have been recorded in the littoral regions of the lake and its coastal waters during 2009/2010. They belong to subclass Orthogastropoda (50 taxa). 21 species out of 50 are recorded in the adjacent waters: 13 of them settle both the adjacent waters and the Lake, while 8 strictly inhabit the adjacent waters. In terms of endemism, 17 are endemic and 4 cosmopolitan. The remainig 29 (out of 50 recorded) settle up only the littoral zone of the Lake: 25 are endemic and 4 are cosmopolitan. The percentage of endemism based on the recorded species for the class Gastropoda is 84%.