A Structure for 261C, a Novel Tricylic Alkaloid from the Madagascan Poison Frog, Mantella betsileo

Convergent evolution of chemical defense in poison frogs and arthropod prey between Madagascar and the Neotropics

“…2). Two SpiroPs, 236 and 252A, have been previously reported in M. baroni (4), and 252B has been reported in Australian Pseudophryne frogs (5). Ant alkaloid 3,5-ds indolizidine 195B and beetle alkaloid precoccinelline 193C, both of which have also been reported in Neotropical dendrobatid and bufonid poison frogs, were detected here for what we believe to be the first time in poison frogs of Madagascar (Tables 1-3).…”

“…These shared alkaloids are unknown for all other genera within Mantellidae, Dendrobatidae, and Bufonidae. There is no doubt that alkaloid sequestration represents an apomorphic trait within each family and that the evolution of alkaloid sequestration for poison frogs in Madagascar and the Neotropics has independently occurred Table 1 multiple times (4,45). Evolutionary convergence of defensive alkaloid sequestration, similarly, has also driven evolutionary convergence for aposematic colorations, presumably in response to similar selective pressures from frog predators to this form of chemical defense.…”

“…Poison frogs have been recognized in four families: South American Melanophyrniscus (Bufonidae); Australian Pseudophryne (Myobatrachidae); Central and South American Dendrobates, Epipedobates, and Phyllobates (Dendrobatidae); and Malagasy (Madagascan) Mantella (Mantellidae) (1,(4)(5)(6)(7)(8). Additionally, trace amounts of such alkaloids have been detected in a Thai ranid frog, Limnonectes kuhli (9).…”

“…In addition to their ability to sequester and accumulate alkaloids from diet, Mantella and some dendrobatid frogs also share the following features: terrestrial eggs, small body size (Ͻ50-mm snout-vent length), toothless jaws, a specialist diet composed largely of ants, active diurnal foraging behaviors, and aposematic coloration; all features are considered to have been produced by convergent evolution (4,(41)(42)(43)(44)(45). In both groups, sequestered defensive chemicals appear to be closely associated with (i) the evolution of aposematism, as a visual warning of their toxicity to potential predators, and (ii) active diurnal foraging, a behavior that is generally rare in frogs (46).…”

“…More than 100 alkaloids of 12 classes have been detected in skin of Mantella (1,4,6,(39)(40), and many also occur in Neotropical poison frogs. In addition to their ability to sequester and accumulate alkaloids from diet, Mantella and some dendrobatid frogs also share the following features: terrestrial eggs, small body size (Ͻ50-mm snout-vent length), toothless jaws, a specialist diet composed largely of ants, active diurnal foraging behaviors, and aposematic coloration; all features are considered to have been produced by convergent evolution (4,(41)(42)(43)(44)(45).…”