Below left: Uakari Poison Frog
(Ranitomeya uakarii) from the
Amazonian lowland rainforest. Image
by Dirk Ercken.
Right: the Golden Poison Frog
(Phyllobates terribilis) is the most
toxic of all dendrbatid species. Image
by Rosa Jay.
Below: the Green-and-black Poison
Dart Frog (Dendrobates auratus) is
native to the tropical rainforest of
Central and South America. Image by
Dirk Ercken.
between aposematic colouration and
toxicity across species, whereby the
most brightly coloured species or
populations are the most toxic. For
example, across 10 populations of
O. pumilio, variation in toxicity was
strongly positively correlated with
frog colouration brightness and
conspicuousness based on avian
vision, indicating that the poison
frog colours were honest signals of
unpalatability to predators, and
creating a strong selective pressure
for the evolution of aposematic
colouration.
But aposematic colouration in
dendrobatids has since undergone
both interspecific and intraspecific
divergences, producing a wide
variety of colours and patterns. The
taxonomy of dendrobatids has there-
fore been thrown into a state of flux.
Distinguishing a species can be very
taxing, as many species are polymor-
phic, with a wide variation in colour
and pattern, and some forms can
closely resemble other species.
Interestingly, there are two instances
(Allobates zaparo and Hyloxalus
nexipus), in which conspicuous
aposematic colouration has evolved
without being a ‘truthful’ indicator
of toxicity. Tellingly, A. zaparo is
known to be a Batesian mimic of the
toxic species Ameerega bilinguis and
Ameerega parvula with which it is
sympatric. Aposematic species are
often dietary specialists, preying
upon ants, from which they sequester
defensive alkaloids.