Gj. Vermeij et G. Rosenberg, GIVING AND RECEIVING - THE TROPICAL ATLANTIC AS DONOR AND RECIPIENT REGION FOR INVADING SPECIES, American malacological bulletin, 10(2), 1993, pp. 181-194
After the middle Pliocene uplift of the Central American seaway (3.1 t
o 3.6 million years ago), the western Atlantic fauna became isolated f
rom that of the eastern Pacific, but connections with the tropical Ind
o-West-Pacific and eastern Atlantic were maintained. By analyzing the
distibution, fossil record, and relationships of shallow-water shell-b
earing molluscs (those living in less than 100 m depth) in die western
Atlantic, we ascertained the extent to which the western Atlantic has
served as a recipient and as a donor region for invading taxa. At lea
st 33 species in the western Atlantic are late Pliocene or Pleistocene
invaders from the Indo-West-Pacific (17 species) or eastern Atlantic
(16 species), whereas at least 39 species dispersed eastward across th
e Atlantic from die Americas to West Africa. Eleven species derived fr
om the Indo-West-Pacific are included in both tallies, because they pr
obably first dispersed westward from the Indian Ocean around southern
Africa to Brazil and the Caribbean region before spreading eastward ac
ross the Atlantic to West Africa. Most of this dispersal is probably b
y means of planktonic larvae, but some species could have been spread
as rafting adults. Oceanic currents and prior extinction histories det
ermine the pattern of interchange among tropical marine biotas. Within
the tropics, the western Atlantic suffered the greatest molluscan ext
inctions since the early Pliocene (about 60 to 70%); it is also the re
gion in which the great majority of immigrants have become common and
geographically widespread. Extinction in die eastern Atlantic, eastern
Pacific, and Indo-West-Pacific has been much less, and immigrants to
these regions often have restricted geographical distribution there, a
nd could be represented by populations that are not self-sustaining.