Biogeographical Problems of the Red Sea Area Exemplified by Hydroids
287
systematic discussion. The number of species in each group will increase with further
studies. On the other hand, these results could reduce (esp. the AM species) or increase
the number of known Suez Canal migrants in both directions. In future, if the faunistic
regions are more intermingled, it will become increasingly difficult to determine the
migratory route of a hydroid.
Zoogeographers are frequently confronted with the decision to divide species and
(local) varieties. Often literature gives no certain help and it is necessary to study the
available material. The synonymy in the case of the hydroids is rather complicated and
makes decisions difficult. A further problem occurs when it is stated that a species is
well distributed. How often must it be recorded and from how many regions of an area?
Thus the author's division into different groups may not be accepted without reservations.
The present results show 5 Mediterranean species which have been transported into
the Red Sea and only 2 which penetrated the opposite way, a proportion which is normally
reserved (STEINITZ, 1968). This might be caused by the absence of coral reefs and of any
extensive rocky substrata in the eastern Mediterranean. At a radius of some 200 km,
NE of Port Said the bottom is covered, almost exclusively by sediment which provides
good conditions for only a few species of hydroids.
287
systematic discussion. The number of species in each group will increase with further
studies. On the other hand, these results could reduce (esp. the AM species) or increase
the number of known Suez Canal migrants in both directions. In future, if the faunistic
regions are more intermingled, it will become increasingly difficult to determine the
migratory route of a hydroid.
Zoogeographers are frequently confronted with the decision to divide species and
(local) varieties. Often literature gives no certain help and it is necessary to study the
available material. The synonymy in the case of the hydroids is rather complicated and
makes decisions difficult. A further problem occurs when it is stated that a species is
well distributed. How often must it be recorded and from how many regions of an area?
Thus the author's division into different groups may not be accepted without reservations.
The present results show 5 Mediterranean species which have been transported into
the Red Sea and only 2 which penetrated the opposite way, a proportion which is normally
reserved (STEINITZ, 1968). This might be caused by the absence of coral reefs and of any
extensive rocky substrata in the eastern Mediterranean. At a radius of some 200 km,
NE of Port Said the bottom is covered, almost exclusively by sediment which provides
good conditions for only a few species of hydroids.