128
The Migrant Biota
For a statistical analysis the number of migrant species is too small, since
specific information on each species of this extremely diversified list is quite
unequal. Therefore, number symbols have been used in an attempt to express the
parameters of the time-distance analysis which will be presented below. The
analysis of the faunal diversity of the migrants and of their success as colonizers
will, for purposes of elarity, follow the time-distance analysis, rather than precede
it.
The information compiled here is by necessity based on incomplete records,
an uneven amount of data, both in time and,space with regard to the different
taxa, as is the raw material on which every zoogeographical analysis of whole
faunas is always based. There has never been a sustained effort in this area crisscrossed by political and cultural boundaries. The different taxa of Lessepsian
migrants, besides the fact that they behave differently on the zoogeographical
scene are also better or less known on the taxonomie and distributional level.
Nevertheless, an attempt to quantify the conelusions has been made, not only
to avoid wordiness or to better express conelusions which were known apriori,
but also in the hope of obtaining new insights into the migration phenomenon.
3.5 Time-Distance Analysis
193 of the 204 species were divided into the categories reported below (see
Table 5). Ofthese, 119 or 61.65% are known to have progressed through the Suez
Canal before invading the Mediterranean. The remaining 74 species or 38.35%
have not been reported from the Suez Canal either due to incomplete records or
because they passed the Canal in "one jump" (without having established stable
populations in the waterway). Since it is reasonable to assume that at least half of
these 74 species do in fact have (or did have) Suez Canal populations, one can
ass urne that the great majority of the Lessepsian migrants (tentatively 80%) are
indeed recruited from species which were able to build up populations in the Suez
Canal environments.
A second point to be analyzed is more complicated: namely, the correlation
which exists between three parameters: (1) the date of settlement of a given species in the Suez Canal; (2) the speed of its migration into the Mediterranean; and
(3) the area it occupies in the Mediterranean.
For these three parameters I have used a set of three-digit symbols, ranging in
the first two cases from "early" to "late", and in the third case from "elose" to
"distant". The species not reported from the Suez Canal are designated by 4.0.0.
In a 3-digit symbol each of the three parameters will have their specific position.
1. The first parameter, "date of the first report in the canal", is subdivided as
follows:
1.0.0 Species reported from the canal before 1906. This period ineludes the
collections by Fuchs, Keller, Krukenberg, Tillier and Bavay (see Chap. 2.2).
2.0.0 Species reported from the Canal before 1930. This period ineludes the
extensive collections ofthe Cambridge Expedition of 1924.
The Migrant Biota
For a statistical analysis the number of migrant species is too small, since
specific information on each species of this extremely diversified list is quite
unequal. Therefore, number symbols have been used in an attempt to express the
parameters of the time-distance analysis which will be presented below. The
analysis of the faunal diversity of the migrants and of their success as colonizers
will, for purposes of elarity, follow the time-distance analysis, rather than precede
it.
The information compiled here is by necessity based on incomplete records,
an uneven amount of data, both in time and,space with regard to the different
taxa, as is the raw material on which every zoogeographical analysis of whole
faunas is always based. There has never been a sustained effort in this area crisscrossed by political and cultural boundaries. The different taxa of Lessepsian
migrants, besides the fact that they behave differently on the zoogeographical
scene are also better or less known on the taxonomie and distributional level.
Nevertheless, an attempt to quantify the conelusions has been made, not only
to avoid wordiness or to better express conelusions which were known apriori,
but also in the hope of obtaining new insights into the migration phenomenon.
3.5 Time-Distance Analysis
193 of the 204 species were divided into the categories reported below (see
Table 5). Ofthese, 119 or 61.65% are known to have progressed through the Suez
Canal before invading the Mediterranean. The remaining 74 species or 38.35%
have not been reported from the Suez Canal either due to incomplete records or
because they passed the Canal in "one jump" (without having established stable
populations in the waterway). Since it is reasonable to assume that at least half of
these 74 species do in fact have (or did have) Suez Canal populations, one can
ass urne that the great majority of the Lessepsian migrants (tentatively 80%) are
indeed recruited from species which were able to build up populations in the Suez
Canal environments.
A second point to be analyzed is more complicated: namely, the correlation
which exists between three parameters: (1) the date of settlement of a given species in the Suez Canal; (2) the speed of its migration into the Mediterranean; and
(3) the area it occupies in the Mediterranean.
For these three parameters I have used a set of three-digit symbols, ranging in
the first two cases from "early" to "late", and in the third case from "elose" to
"distant". The species not reported from the Suez Canal are designated by 4.0.0.
In a 3-digit symbol each of the three parameters will have their specific position.
1. The first parameter, "date of the first report in the canal", is subdivided as
follows:
1.0.0 Species reported from the canal before 1906. This period ineludes the
collections by Fuchs, Keller, Krukenberg, Tillier and Bavay (see Chap. 2.2).
2.0.0 Species reported from the Canal before 1930. This period ineludes the
extensive collections ofthe Cambridge Expedition of 1924.