Melyrid beetles ( Choresine ): A putative source for the batrachotoxin alkaloids found in poison-dart frogs and toxic passerine birds

Abstract

Batrachotoxins are neurotoxic steroidal alkaloids first isolated from a Colombian poison-dart frog and later found in certain passerine birds of New Guinea. Neither vertebrate group is thought to produce the toxins de novo, but instead they likely sequester them from dietary sources. Here we describe the presence of high levels of batrachotoxins in a little-studied group of beetles, genus Choresine (family Melyridae). These small beetles and their high toxin concentrations suggest that they might provide a toxin source for the New Guinea birds. Stomach content analyses of Pitohui birds revealed Choresine beetles in the diet, as well as numerous other small beetles and arthropods. The family Melyridae is cosmopolitan, and relatives in Colombian rain forests of South America could be the source of the batrachotoxins found in the highly toxic Phyllobates frogs of that region.Pitohui ͉ Ifrita ͉ Phyllobates ͉ APCI mass spectrometry ͉ dietary arthropods

Phylogeny of the avian genus Pitohui and the evolution of toxicity in birds

“…In the likelihood and Bayesian phylogenies, P. kirhocephalus is monophyletic as well, however, the support is poor, and parsimony analyses do not unequivocally support this monophyly. The confusing variation within this species has been long recognized (Beehler et al, 1986) and results from three highly differentiated genetic groups within P. kirhocephalus that distinguish the north-coast, south-coast, and West Papuan Island clades (Dumbacher et al, 2004). Other analyses directed at biogeography continue to support further splitting P. kirhocephalus (Dumbacher, Fig.…”

“…This in no way precludes that the toxins have an anti-ectoparasite function as well. Instead, we suggest that the toxins are likely ''broad spectrum" poisons that offer a variety of advantages (Dumbacher et al, 2004).…”

“…By mapping these data on a phylogeny using likelihood and MCMC techniques, our analyses suggested that toxicity evolved several times independently within the core corvoidea, and that toxicity is not ancestral within corvoids. Other data suggest that pitohuis are insensitive to batrachotoxins and that they likely sequester toxins from their diet (Dumbacher et al, 2004). These may be key innovations that allowed toxin sequestration to evolve multiple times, and this warrants future research.…”

Polyphyletic origin of toxic Pitohui birds suggests widespread occurrence of toxicity in corvoid birds

“…P. nigrescens, a mildly toxic species, is sister to all true Pachycephala whistlers, whereas the mildly toxic P. cristatus is closely related to Aleadryas rufinucha, a species distantly related to the Pachycephala radiation. P. ferrugineus, which has often been found to be devoid of batrachotoxins (Dumbacher et al 2004), is closely related to the Australo-Papuan Colluricincla shrike-thrushes, which were also demonstrated to have traces of batrachotoxins (Dumbacher et al 2004). I. kowaldi is not closely related to any Pitohui species.…”

“…It was also found that the bird Ifrita kowaldi contained a similar spectrum of batrachotoxins as Pitohui. At the time, however, no reliable phylogenetic framework was available to determine the relationship between Ifrita and Pitohui, and thus whether the ability to tolerate this toxin in the body is restricted to a specific avian lineage (Dumbacher et al 2004).…”