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Abstract SPECIATION ON A ROUND PLANET: PHYLOGEOGRAPHY OF THE GOATFISH MULLOIDICHTHYS. Harilaos A. Lessios and D. Ross Robertson The goatfish Mulloidichthys is a pantropical genus, abundant
on most coral reefs of the world. We constructed a mitochondrial
DNA phylogeny of its species, based on the entire ATPase 8 and 6
coding region (843 bp) and the 5' end of the control region (582
bp). The reconstruction revealed that the Indo-Pacific M. phlugeri
diverged first, followed by M. flavolineatus, also
from the Indo-Pacific, followed by the Atlantic M. martinicus,
which is an outgroup to a polytomy composed of the eastern Pacific
M. dentatus and the Indo-Pacific M. vanicolensis
and M. mimicus. Genetic divergence in previously published
isozyme evidence agrees with the phylogenetic placement of these
species by mtDNA. The divergence between M. martinicus
and the Pacific tritomy is significantly smaller than divergence
in the same DNA fragment in six other fish genera likely to have
been split by the rise of the Isthmus of Panama 3.1 mya. Mulloidichthys,
therefore, is likely to have maintained genetic contact between
the Atlantic and the Indian Ocean around the tip of S. Africa and
through the Benguela upwelling up until the Pleistocene. Gene flow
within each of the species is high, even over different oceanic
regions. M. vanicolensis, in particular, which was formerly
thought as not distributed East of the Central Pacific, is actually
found in abundance at the Clipperton Atoll and even at the shore
of the Americas.
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