Bocas del Toro Research Station - Smithsonian Tropical Research ...

OSCAR PUEBLA, FREDERIC GUICHARD
AND ELDREDGE BERMINGHAM
McGill University and STRI
Color pattern as a “magic trait” driving
ecological speciation of Hypoplectrus coral reef
fishes
A well-documented mechanism for the formation
of new species, referred to as allopatric speciation,
hypothesizes that new species are established when
a geographic barrier such as a mountain range
emerges. Animal populations separated by a barrier
follow distinct evolutionary trajectories due to
chance and to different environmental conditions.
Ultimately, they may become reproductively
isolated and a new species is formed.
Geographical barriers are not obvious in marine
systems except at the scale of entire ocean basins,
e.g., the separation of the Atlantic and Pacific
Oceans by the Isthmus of Panama. It is therefore
not clear to what extent allopatric speciation can
account for the high diversity of marine ecosystems.
Another, more controversial, mechanism of
speciation posits that a new species is established
when one population splits through ecological
processes, without geographical separation. Puebla
and colleagues’ work on Caribbean coral reef fishes
of the genus Hypoplectrus presents one of the few
potential cases of ecological speciation documented
in the marine realm.
They have shown that sympatric Hypoplectrus
color morphs mate assortatively and are genetically
distinct, and can therefore be considered incipient
species. Furthermore, they have identified ecological
conditions conducive to speciation by presenting
behavioral evidence of aggressive mimicry, whereby
predatory color morphs mimic the color patterns
of non-predatory reef fish species to increase their
success as they approach and attack prey.
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Can ecological processes drive speciation? Hypoplectrus coral reef fish
mimic the colors of other fish on the reef. This mimicry prevents their prey
from recognizing them as predators.
By censusing fish along the reef, researchers begin to understand the
evolutionary dynamics of coloration and mate choice.