Evolution in Family Dendrobatidae (Poison Frogs)

Introduction

The family Dendrobatidae, part of the class Amphibia, and more broadly, the kingdom Animalia, are a group of toxic frogs. These animals are commonly referred to as poison arrow frogs, dart poison frogs, or poison dart frogs. Frogs within this family are found living in the tropical climates of Central America and the northern portion of South America. They are usually small in size, and are known for their vivid coloration, although there are exceptions to this trait. Their diet consists of ants and mites, which research has suggested are suppliers of the precursor molecules that make up the amphibians toxins. Frogs in this family derive their common name from the Columbian practice of rubbing blow darts on the backs of frogs to coat them in poison for hunting. They produce alkaloid poisons, and some of the most highly toxic ones known at that. Many species’ toxins are strong enough to be lethal to vertebrates in even a small dose.

Examples of bright coloration found in various species within the Dendrobatidae family. Image source

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Evolution

Phylogenetic tree of the four genera of Dendrobatidae used by Summers and Clough with representative species of each pictured.

Coloration and Toxicity
Members of the amphibian family Dendrobatidae are considered to be aposematic, meaning their coloration serves as an adverse warning that protects them from predation. For this notion to be true, it is implied that the frogs’ bright appearance and toxicity would have evolved in parallel. Research conducted by Summers and Clough set out to prove this hypothesis. Previously to this study, investigations of this hypothesis failed to account for phylogenetic relationships, which can cause a bias in results. Summers and Clough, however, made use of mitochondrial DNA from the gene regions cytochrome b, 12s RNA, and 16s RNA, in order to create a phylogenetic basis for their study. From this they developed four genera within the Dendrobatidae: Phyllobates, Dendrobates, Epipedobates, and Minyobates. This wide range of diversity within the family lead the researchers to a comparative method of analysis. For the twenty one representative species from each of the four genera examined in the study, data on toxicity was collected from literature, and coloration rated by both human observers and a computer program. When determining evolutionary correlation between the two phenomena, Comparative analysis on the data using models of both gradual and punctuated evolution showed that they were significantly correlated. The work of Summers and Clough effectively proved that frogs in the family Dendrobatidae, are in fact, aposematic. Their insight into the evolutionary processes in these animals are crucial, and provide an understanding of a constant relationship between two things that still are wildly varied within the group's population.

While species in the family are morphologically very similar to each other, great phenotypic diversity is seen in coloration and patterning. Image source

Self Toxin Resistance

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Microbiome

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References

Edited by Sydney McCallie, student of Joan Slonczewski for BIOL 116 Information in Living Systems, 2020, Kenyon College.