122
The Migrant Biota
Tortonese (1951, p.232) was ofthe opinion that: ''The faunistic poverty ofthe
Eastern Mediterranean is a certain fact not due to the incomplete research ... It is
to assume that future research will demonstrate the eastward extension of some
species but this will not change the present views on the quantitative relationship
between the two great mediterranean basins." The same author (Tortonese, 1973)
later emphasizes the fact that since the "Calypso" cruise in the Aegean sea many
western species have been discovered there. This only proves the necessity for a
good subdivision within the Eastern Mediterranean separating the Aegean from
the Levant Sea.
This becomes especially clear in the careful study made by Fredj (1972, 1974)
on the distribution of 1244 file-indexed species of benthie invertebrates of the
Mediterranean. Unfortunately, when subdividing the Eastern Mediterranean (minus the Adriatie Sea) Fredj distinguishes a N orth Eastern Mediterranean ("Mediterranee orientale de Nord"), a Central Eastern Mediterranean and a South Eastern Mediterranean. While the northern subdivision is a natural one and includes
only the Aegean Sea, the "Central" one extends in a broad zone from the Israel
coast near Haifa, along the Anatolian coast, including the southern part of Greece
together with the big islands, and ends on the western shore of the peninsula near
Corfu. The South-East Mediterranean is only slightly more homogenous since it
comprises the shores from Haifa, along Egypt and Libya, ending at Cape Bon
whieh faces the Straits of Sicily.
Even so, Fredj calculates that the Eastern Mediterranean as a whole contains
only 48.4% of the 1244 species analyzed while the Western Mediterranean contains 92%. The Eastern Mediterranean has only 4.2% of the species strictly
limited to this basin while 35.4% of the species indexed by Fredj can be found
only in the Western Mediterranean. Ofthe 247 endemie species found among the
1244 indexed species (19.8%), 82.2% arefound in the Western Mediterranean and
only 22.8% in the Eastern. Of the total 247 endemie species, 49.8% are exclusive
to the Western Mediterranean and only 4.5% are found exclusively in the Eastern
Mediterranean.
With the exclusion of the Aegean Sea and Greek Peninsula, these figures
would have been more impressively in disfavor of the species diversity of the
Levant Basin. One must also keep in mind the limitation of the method used by
Fredj, who artificially selected the animal groups whieh form his species list: the
main groups are the Echinodermata, Polychaeta, Sipuncula, Solenogastres, Polyplacophora, Scaphopoda, Pelecypoda, Cephalopoda, and Decapoda. The Gastropoda are not included, and the Polychaeta, a group in whieh the distributional
information is still incomplete, form more than one quarter of the 1244 species
studied. Nevertheless, the zoogeographie study of Fredj (1974) is the first noteworthy attempt to quantify the zoogeographie patterns of the Mediterranean
fauna.
Almost all positive traits of the Eastern Mediterranean as a mediterranean
subregion result from the phenomenon of Lessepsian immigration, which should
be analyzed separately. It is difficult to fmd any positive trait in the species
diversity ofthe Levant Basin of one disregards the additions which have occurred
since the opening ofthe Suez Canal.
The Migrant Biota
Tortonese (1951, p.232) was ofthe opinion that: ''The faunistic poverty ofthe
Eastern Mediterranean is a certain fact not due to the incomplete research ... It is
to assume that future research will demonstrate the eastward extension of some
species but this will not change the present views on the quantitative relationship
between the two great mediterranean basins." The same author (Tortonese, 1973)
later emphasizes the fact that since the "Calypso" cruise in the Aegean sea many
western species have been discovered there. This only proves the necessity for a
good subdivision within the Eastern Mediterranean separating the Aegean from
the Levant Sea.
This becomes especially clear in the careful study made by Fredj (1972, 1974)
on the distribution of 1244 file-indexed species of benthie invertebrates of the
Mediterranean. Unfortunately, when subdividing the Eastern Mediterranean (minus the Adriatie Sea) Fredj distinguishes a N orth Eastern Mediterranean ("Mediterranee orientale de Nord"), a Central Eastern Mediterranean and a South Eastern Mediterranean. While the northern subdivision is a natural one and includes
only the Aegean Sea, the "Central" one extends in a broad zone from the Israel
coast near Haifa, along the Anatolian coast, including the southern part of Greece
together with the big islands, and ends on the western shore of the peninsula near
Corfu. The South-East Mediterranean is only slightly more homogenous since it
comprises the shores from Haifa, along Egypt and Libya, ending at Cape Bon
whieh faces the Straits of Sicily.
Even so, Fredj calculates that the Eastern Mediterranean as a whole contains
only 48.4% of the 1244 species analyzed while the Western Mediterranean contains 92%. The Eastern Mediterranean has only 4.2% of the species strictly
limited to this basin while 35.4% of the species indexed by Fredj can be found
only in the Western Mediterranean. Ofthe 247 endemie species found among the
1244 indexed species (19.8%), 82.2% arefound in the Western Mediterranean and
only 22.8% in the Eastern. Of the total 247 endemie species, 49.8% are exclusive
to the Western Mediterranean and only 4.5% are found exclusively in the Eastern
Mediterranean.
With the exclusion of the Aegean Sea and Greek Peninsula, these figures
would have been more impressively in disfavor of the species diversity of the
Levant Basin. One must also keep in mind the limitation of the method used by
Fredj, who artificially selected the animal groups whieh form his species list: the
main groups are the Echinodermata, Polychaeta, Sipuncula, Solenogastres, Polyplacophora, Scaphopoda, Pelecypoda, Cephalopoda, and Decapoda. The Gastropoda are not included, and the Polychaeta, a group in whieh the distributional
information is still incomplete, form more than one quarter of the 1244 species
studied. Nevertheless, the zoogeographie study of Fredj (1974) is the first noteworthy attempt to quantify the zoogeographie patterns of the Mediterranean
fauna.
Almost all positive traits of the Eastern Mediterranean as a mediterranean
subregion result from the phenomenon of Lessepsian immigration, which should
be analyzed separately. It is difficult to fmd any positive trait in the species
diversity ofthe Levant Basin of one disregards the additions which have occurred
since the opening ofthe Suez Canal.