16
R. K. DELL
problems of definition are more difficult. Here especially a study of the
dynamics of biological migration will surely prove more fruitful than
the static studies which working within a provincial concept often
engender.
D. Endemism
Most systematists dealing with Antarctic organisms are interested
in the degree of endemism. Some few have been strong minded enough
not to calculate the percentage, or at least not to publish the results.
Most of us, while admitting the incomplete data with which we work,
persuade ourselves to carry out the exercise and publish the results.
The degree of endemism is of course of special interest for the Antarctic
since it is one of the few " objective " measures we have for the degree
to which the Antarctic fauna and flora has been isolated, and thus a
measure of the age of the biota. As such these calculations are beloved
by biogeographers. One biogeographer has recently assembled a long
list of the endemism percentages (Cailleux, 1961) given by authors for
Antarctic plants and animals, recent and fossil, marine, freshwater and
terrestrial. A somewhat modified extract from this list as it relates to
Antarctic benthic organisms is given in Table I.
There are now more up to date figures for some of these groups, but
Cailleux had demonstrated that taking the figures given by subsequent
workers for any one group may have changed the actual figures but the
general order of magnitude remains roughly the same. Some successive
percentages for a few groups illustrate this point (Cailleux, 1961).
Sponges
42 44 67 67%
Pycnogonids
84 80 80 91%
Marine isopods
45 78%
Ascidians
57 a4y0
The general high percentages listed by Cailleux ranging from 31 to
96% for a large number of animal groups bears striking testimony to
the independent character of the Antarctic fauna.
Cailleux even gave mean values for marine organisms (67%),
terrestrial organisms (57y0), marine fossils (60%) and terrestrial fossils
(62%). Whatever precise value such calculations may have, the figures
are remarkably consistent and they are remarkably high. It is hard to
escape the belief, when considering degrees of endemism of this magnitude, that the biota of the Antarctic has been isolated for a long time.
Whatever the history of the presence of a modern migration route in
the form of the Scotia Arc, two conclusions seem inevitable:
R. K. DELL
problems of definition are more difficult. Here especially a study of the
dynamics of biological migration will surely prove more fruitful than
the static studies which working within a provincial concept often
engender.
D. Endemism
Most systematists dealing with Antarctic organisms are interested
in the degree of endemism. Some few have been strong minded enough
not to calculate the percentage, or at least not to publish the results.
Most of us, while admitting the incomplete data with which we work,
persuade ourselves to carry out the exercise and publish the results.
The degree of endemism is of course of special interest for the Antarctic
since it is one of the few " objective " measures we have for the degree
to which the Antarctic fauna and flora has been isolated, and thus a
measure of the age of the biota. As such these calculations are beloved
by biogeographers. One biogeographer has recently assembled a long
list of the endemism percentages (Cailleux, 1961) given by authors for
Antarctic plants and animals, recent and fossil, marine, freshwater and
terrestrial. A somewhat modified extract from this list as it relates to
Antarctic benthic organisms is given in Table I.
There are now more up to date figures for some of these groups, but
Cailleux had demonstrated that taking the figures given by subsequent
workers for any one group may have changed the actual figures but the
general order of magnitude remains roughly the same. Some successive
percentages for a few groups illustrate this point (Cailleux, 1961).
Sponges
42 44 67 67%
Pycnogonids
84 80 80 91%
Marine isopods
45 78%
Ascidians
57 a4y0
The general high percentages listed by Cailleux ranging from 31 to
96% for a large number of animal groups bears striking testimony to
the independent character of the Antarctic fauna.
Cailleux even gave mean values for marine organisms (67%),
terrestrial organisms (57y0), marine fossils (60%) and terrestrial fossils
(62%). Whatever precise value such calculations may have, the figures
are remarkably consistent and they are remarkably high. It is hard to
escape the belief, when considering degrees of endemism of this magnitude, that the biota of the Antarctic has been isolated for a long time.
Whatever the history of the presence of a modern migration route in
the form of the Scotia Arc, two conclusions seem inevitable: