Biology Reference
In-Depth Information
Figure 9.6. Geographical distribution of 18 species of Scomberomorus, 2 species of
Grammatorcynus, 23 species of Copepoda and 17 species of Monogenea. Species
numbers restricted to certain seas are given beside the large circles which indicate
different seas, numbers of species shared by different seas are given near or on the lines
that indicate sharing. Circles: fish; squares: copepods; triangles: Monogenea. Note:
the Indian Ocean is defined as not including the coastal zone along the west coasts of
Malaysia, Indonesia and Australia. Note: one copepod species only recorded from
Port Elizabeth, South Africa, but not from the rest of the Indian Ocean, hence
connection between W. Pacific and Indian Ocean indicated by dotted line. The
result shows that not a single species (with the exception of four circumtropical ones)
is shared by the eastern Pacific and western Pacific. Reprinted from Rohde, and
Hayward (
2000
), with permission from Elsevier.
differences in diversity between oceans. Species of Scomberomorus and
Grammatorcynus in seas of low diversity have relatively more parasite species
than those in seas of high diversity. However, when considering only
endemic fish and parasite species, the two centers of diversity, i.e., the
Indo-West Pacific and the West Atlantic, have parasite/host ratios (
ΒΌ
relative
species richnesses) of 1.75 and 1.25, respectively, versus a ratio of 1.00 for
all other seas. These differences in relative species richness in different seas
suggest that more parasite species could be accommodated at least in the
poorly infected fish; the differences in relative species richnesses of ende-
mic and all parasite species suggest that historical factors are responsible for
the differences. Apparently, fish in low-diversity regions have acquired
