Anatomical evidence of close affinity between endemic species of Pisidium (Bivalvia, Sphaeriidae) from some ancient lakes, and the widely distributed taxa

Abstract

Anatomical characters of three endemic taxa from the Balkan lakes Ohrid and Prespa and one species from Lake Baikal were studied and compared with those of the widely distributed species of Pisidium. A close affinity of Pisidium edlaueri Kuiper 1960 from Ohrid and Pisidium maasseni Kuiper 1987 from Prespa to the Holarctic Pisidium nitidum Jenyns 1832 was confirmed; Pisidium raddei Dybowski 1902 from Baikal is anatomically identical to the Boreo-alpine Pisidium conventus Clessin 1877. Similarity in anatomical characters between the Ohridan subspecies Pisidium subtruncatum recalvum Kuiper 1960 and the nominal subspecies was also shown. These findings are compared with the situation in other ancient lakes. The similarity in some shell characters between the nonrelated taxa inhabiting these lakes is interpreted as being the result of convergent evolution.