Folia Historico-Naturalia Musei Matraensis - A Mátra Múzeum Természetrajzi Közleményei 9. (1984)

Kinzelbach, R. K.–Roth, G.: Patterns of distribution of some freshwater molluscs of the Levant region

PATTERNS OF DISTRIBUTION OF SOME SELECTED SPECIES i. Unio elongatulus eucinus (BOURGUIGNAT, 1857) (Fig. 1). Middle Eastern subspecies of Unio elognatulus C. PFEIFFER, 1825, formerly Unio mancus (LAMARCK), which is known from the western Mediterranean since the Pliocene and which spread eastward through southern Greece (e. g. Lake of Kopias) and Anatolia (e. g. Lake Sugla near Konya) as far as Iran. Starting from the Çukurova region this species colonized many of the Levantine coastal rivers down to Palestine but was unable to invade the Levantine rift valley. Further south it reached the Nile, where it is represented by the subspecies dembeae SOWERBY (MODELL 1951). Its occurence in the lower course of the Orontes river indicates, that this part of the Orontes was a coastal river in the past. The rivers Quwaiq and Sagur were colonized by this mussel from the Euphrates system, after their being separated from the Orontes. 2. L7m'o terminális terminális (BOURGUIGNAT, 1852) (Fig. 2). According to MODELL (1951) Unio terminális originated from the Lower Danube and reached the Levant region through the Vardar depression and the Levant region throught the Vardar depression and the Egean lakes. As an easily distinguishable subspecies, U. t. terminális, it appeared within the Antakya basin (Amik Gölü) and the Gab rift valley during the Pliocene and disappeared from there during the Pleistocene. In the southern Levantine rift valley this subspecies still exists,- it invaded the Nahal Quison, using the Yisrce'l plain as a pathway. 3. Unio terminális delicatus (LEA, 1863) (Fig. 2). After the extinction of 17. t. terminális in the northern Levantine rift valley the region was colonized by L7. t. delicatus from southern Anatolia. At this time there were no connections from the Orontes to the Quwaiq nor to the Euphrates. A short termed connection between the upper Orontes and the Mediterranean Sea via the Gate of Horns during the late Pleistocene allowed U. t. delicatus to penetrate into the Nahr al-Kabir (S) and several temporarily connected rivulets north of its mouth. An isolated occurence in the Lake of Muzairib was caused by recent introduction, maybe by fishes of the genus Tilapia from fish-hatcheries of the Gab. The two taxa listed here as subspecies are possibly already isolated at the specific level. 4. Corbicula fluminalis (O. F. MÜLLER, 1774) (Fig. 3). Within the Levant this species, which already during the Tertiary was widely spread in Africa and the Middle East, was originally restricted to the entire Levantine rift valley. Apparently, it invaded this area coming from the Euphrates system. During the Pleistocene it dispersed into the 116