Dendrobates

Abstract: Aposematism is the association, in a prey organism, of the presence of a warning signal with unprofitability to predators. The origin of aposematism is puzzling, because of its predicted low probability of establishment in a population due to the prey's increased conspicuousness. Aposematism is a widespread trait in invertebrate taxa, but, in vertebrates, it is mostly evident in amphibians, reptiles, and fishes. Poison frogs (Dendrobatidae) are one of the most well known examples of the co-occurrence of warning coloration and toxicity. This monophyletic group of mostly diurnal leaf-litter Neotropical anurans has both toxic/colorful and palatable/cryptic species. Previous studies suggested a single origin of toxicity and warning coloration, dividing the family in two discrete groups of primitively cryptic and more derived aposematic frogs. Recent molecular phylogenetic analyses using mostly aposematic taxa supported this conclusion and proposed a single tandem origin of toxicity and conspicuous warning coloration. By using expanded taxon and character sampling, we reexamined the phylogenetic correlation between the origins of toxicity and warning coloration. At least four or five independent origins of aposematism have occurred within poison frogs; by using simulations, we rejected hypotheses of one, two, or three origins of aposematism (P < 0.002). We also found that diet specialization is linked with the evolution of aposematism. Specialization on prey, such as ants and termites, may have evolved independently at least two times.

Abstract: Litter frogs at two rainforest locations in Panama elect prey in a pattern similar to that found for litter frogs in lowland Peru (Toft, 1980) despite differences in the frog fauna between Panama and Peru. Species of litter frogs form a continuum from species that specialize on ants and mites, through generalists, to species that avoid ants and mites. Modes of foraging and predator defense and taxa of litter frogs are correlated with position along the continuum. Atelopus and Bufo (Bufonidae) and Dendrobates (Dendrobatidae) are poisonous, searching foragers which eat many small prey, primarily ants and mites, per day. Colostethus (Dendrobatidae) eat ants, but to a lesser degree, and have a more sedentary foraging behavior than Dendrobates. Eleutherodactylus (Leptodactylidae) are cryptic, sit-and-wait foragers which eat few large prey per day, with the exception of E. vocator, which eat ants in proportion similar to Colostethus. Evidence within the Dendrobatidae suggests that specialization on ants is derived from a generalized mode of foraging. Ecological correlates of foraging mode in litter anurans are summarized and are generally similar to

Abstract: Poison frogs (Family Dendrobatidae) are common leaf litter inhabitants of New World tropical rainforests. The name of this group derives from several genera (especially Dendrobates, Minyobates, and Phyllobates) that are aposematically coloured and have toxic skin to varying degrees. Other species in the family, primarily the genus Colostethus, are cryptically coloured and non-toxic. Recent studies have revealed that the toxic compounds in the skin, which are lipophilic alkaloids, may have a dietary origin. Diets and associated characteristics, prey size, prey number, and niche breadth, of nine species in five genera, three of which have poisonous species, were examined. Interpretation of these characteristics in light of an independently constructed cladogram revealed the inclusion of a high percentage of Formicidae (ants) in the diets of toxic species. Although alkaloids have been reported in several insect groups, more alkaloids are known from ants than any other group. Species in the genus Dendrobates, which are poisonous and have many other derived characters, have diets composed of 50–73% ants, whereas percentages of ants used by non-toxic species in the genus Colostethus was 12–16%. Ants are the major prey category consumed by the five poisonous species considered in this study. In general, frogs separated into two groups. More basal groups with non-toxic skin and cryptic coloration had diets with low percentages of ants, low numbers of prey per individual, and high niche breadths, indicating inclusion of a broad range of prey categories in their diets. Species with poisonous skin and aposematic coloration had diets with large percentages of ants, large numbers of prey per individual, and low niche breadths, indicating diets with relatively few prey categories. Thus, diet, and the subsequent evolution of uptake systems for alkaloids, may be the primary character that led to the development of toxic skin and permitted aposematism, leading to radiation of poisonous species.