Description | The poison frogs (family Dendrobatidae) are terrestrial anuran
amphibians displaying a wide range of coloration and toxicity.
These frogs generally have been considered to be aposematic, but
relatively little research has been carried out to test the predictions
of this hypothesis. Here we use a comparative approach to test one
prediction of the hypothesis of aposematism: that coloration will
evolve in tandem with toxicity. Recently, we developed a phylogenetic
hypothesis of the evolutionary relationships among representative
species of poison frogs, using sequences from three
regions of mitochondrial DNA. In our analysis, we use that DNAbased
phylogeny and comparative analysis of independent contrasts
to investigate the correlation between coloration and toxicity
in the poison frog family (Dendrobatidae). Information on the
toxicity of different species was obtained from the literature. Two
different measures of the brightness and extent of coloration were
used. (i) Twenty-four human observers were asked to rank different
photos of each different species in the analysis in terms of
contrast to a leaf-littered background. (ii) Color photos of each
species were scanned into a computer and a computer program
was used to obtain a measure of the contrast of the colors of each
species relative to a leaf-littered background. Comparative analyses
of the results were carried out with two different models of
character evolution: gradual change, with branch lengths proportional
to the amount of genetic change, and punctuational change,
with all change being associated with speciation events. Comparative
analysis using either method or model indicated a significant
correlation between the evolution of toxicity and coloration across
this family. These results are consistent with the hypothesis that
coloration in this group is aposematic. Originally published Proc Natl Acad Sci, Vol. 98, No. 11, May 2001 | en_US |