The evolution of coloration and toxicity in the poison frog family (Dendrobatidae)

Abstract

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