Travel Reference
In-Depth Information
Tissue samples were ultimately obtained from 13 geographically dis-
tinct nautiloid populations among the "species"
Nautilus pompilius, N.
macromphalus, N.
stenomp/ia!us,
N. belauensis,
and
N. scrobiculatus
from nu-
merous localities in Fiji, Samoa, Australia, New Guinea, the Philippines,
Palau, and New Caledonia. These tissue samples were analyzed first in the
lab of David Woodruff of the University of California at San Diego, using a
technique called gel electrophoretics, and later, using more powerful DNA
sequencing techniques, by geneticist Charles Wray at the American Mu-
seum of Natural History. Both sets of analyses yielded the same surprising re-
sult: Only two distinct groups emerged. One group was composed of
Nautilus
scrobiculatus,
which (according to the molecular "clock" approach of analyz-
ing genetic distance, which compares differences in DNA results to an esti-
mated rate of change in all DNA molecules) appears to have descended from
an unknown
Nautilus
species sometime in the Miocene Epoch, or about 15
million years ago. The other group was composed of all other
Nautilus
"species."
"Nautilus" scrobiculatus
is so different in its gene sequences from
Nautilus
that
David Woodruff suggested to me that it might not even belong in the same
family
as
Nautilus,
let alone the same genus.
The results suggested that not only did the many isolated populations
of N.
pompilius
all fall into the same species (which was at least comforting)
but so too did
N. belauensis, N. stenomphalus,
and (to a slightly lesser extent)
N.
macromphalus.
The genetic results suggested that separating out these lat-
ter as distinct species of
Nautilus
made little biological sense, and indeed
Saunders and I provided independent confirmation of this with our discov-
ery that
Nautilus stenomphalus,
which we captured for the first time alive in
1986, was apparently breeding with
N. pompilius
on the Great Barrier Reef of
Australia.
If the genetic evidence was to be believed, then the long-accepted clas-
sification of the living species assigned to
Nautilus
had crumbled. Not only
did
N. scrobiculatus
appear to represent a different genus, but the slight dif-
ferences in shell morphology of the other species classically placed in
Nau-
tilus
appeared to be of little or no taxonomic significance. We had gone from
five species belonging to one genus, to two genera, each with one species. In-
