|
Vol. 37 No. 4, 1998
Zoogeography of Shore Fishes of the Indo-Pacific Region
John E. Randall
Bernice P. Bishop Museum, 1525 Bernice St., Honolulu, Hawaii 96817-2704, USA
John E. Randall (1998)
The East Indian region (Indonesia, New Guinea, and the Philippines),
with perhaps as many as 2800 species of shore fishes, has the richest
marine fish fauna of the world. The numbers of species of fishes
decline, in general, with distance to the east of the East Indies,
ending with 566 species in Hawaii and 126 at Easter Island. The
richness of the marine fauna of the East Indies is explained in terms
of its relatively stable sea temperature during ice ages, its large
size and high diversity of habitat, in having many families of shore
fishes adapted to the nutrient-rich waters of continental and large
island shelves that are lacking around oceanic islands, in having many
species with larvae unable to survive in plankton-poor oceanic seas or
having too short a life span in the pelagic realm for long transport in
ocean currents, and in being the recipient of immigrating larvae of
species that evolved peripherally. It is also a place where speciation
may have occurred because of a barrier to east-west dispersal of marine
fishes resulting from sea-level lowering during glacial periods (of
which there have been at least 3 and perhaps as many as 6 during the
last 700 000 years), combined with low salinity in the area from river
discharge and cooling from upwelling. There could also have been
speciation in embayments or small seas isolated in the East Indian
region from sea-level lowering. Sixtyfive examples are given of
possible geminate pairs of fishes from such a barrier, judging from
their similarity in color and morphology. Undoubtedly many more remain
to be elucidated, some so similar that they remain undetected today.
Fifteen examples are listed of possible geminate species of the western
Indian Ocean and western Pacific that are not known to overlap in the
East Indies, and 8 examples of color variants in the 2 oceans that are
not currently regarded as different enough to be treated as species.
Five examples of species pairs are cited for the Andaman Sea and
western Indonesia that may be the result of near-isolation of the
Andaman Sea during the Neogene. Explanation is given for distributions
of fishes occurring only to the east and west of the East Indies in
terms of extinction there during sea-level lows. The causes of
antitropical distributions are discussed. The level of endemism of
fishes for islands in the Pacific has been diminishing as a result of
endemics being found extralimitally, as well as the discovery of new
records of Indo-Pacific fishes for the areas. Hawaii still has the
highest, with 23.1% endemism, and Easter Island is a close second with
22.2%. The use of subspecies is encouraged for geographically isolated
populations that exhibit consistent differences but at a level notably
less than that of similar sympatric species of the genus. In order to
ensure continuing stability in our classification of fishes, a plea is
given not to rank characters obtained from molecular and biochemical
analyses higher than the basic morphological characters that are
fundamental to systematics.
Key words: Indo-Pacific, East Indies, Speciation, Endemism, Subspecies.
*Correspondence: Tel: (808) 2351652. Fax: (808) 8478252. E-mail: johne@bishop.bishop.hawaii.org
|
