Strawberry poison frogs feed their babies poison eggs

The Strawberry poison frog lavishes care upon its offspring. In the March issue of Ecology, out Monday the 17th, Stynoski et al. report that the female frog fortifies its progeny with defensive chemicals. Also in this issue: P value debates, arctic warming, and estimating the success of biological invasions.

The strawberry poison frog (Oophaga pumilio or, formerly, Dendrobates pumilio) adorns the cover of the March issue of Ecology, released on Monday. Strawberry darts put extraordinary effort into the care and feeding their tadpoles, including, report Stynoski et al. on page 587, fortifying their young with poison. This female was photographed at La Selva Biological Station in Costa Rica. O. pumilio tolerates some habitat alteration and is sometimes found in Central American gardens. Populations are relatively healthy. The frog is protected from the pet trade by Appendix II of the Convention on International Trade in Endangered Species (CITES) and listed as “least concern” by the IUCN. Credit, author Ralph A. Saporito.

Tiny, toxic, and ostentatiously beautiful, the strawberry poison dart (Oophaga  pumilio) is the kind of frog to lavish care upon its offspring. Both parents put in the hours. Fathers brood over the eggs laid on damp forest floors of lowland Costa Rice, Nicaragua, and Panama, defending them and hauling water to keep them moist.

A phytotelma, or small pool of water, in the center of a bromeliad photographed at the Atlanta Botanical Garden by flikr user *Robin*.

But mom does most of the work. Soon after hatching, tadpoles ride piggyback on their mothers to small pools of water, cupped in the hearts of bromeliad plants. Each tadpole gets its own tiny pool, and mom makes regular rounds to feed them with her own, unfertilized, eggs (oophaga = “egg eater”) until, six weeks later, metamorphosis takes them to adulthood. The unfertilized eggs fortify the tadpoles not only with nutrients, but also poison, Jennifer Stynoski and colleagues report in the March issue of Ecology, online this week.

Dart frogs’ extravagant colors warn predators of the poison in their skin. The frogs extract toxic alkaloids from the mites, formacine ants, millipedes, and beetles that they eat, and store the poisonous compounds in glands in their skin, ready to release when the frogs feel threatened. Prominant O. pumilio’s arsenal are Pumiliotoxins, which affect contraction in the heart and muscles, most likely through voltage-gated calcium channels, causing both hyperactivity and paralysis. The strawberry dart is not the most deadly of the Dendrobatidae, but touching one will make a person very uncomfortable.

Stynoski et al. detected alkaloids in wild-caught O. pumilio tadpoles fed O. pumilio eggs, but not in tadpoles fed nontoxic eggs of the red-eyed treefrog, Agalychnis callidryas. In laboratory experiments, predatory bullet ants (Paraponera clavata) preferred to attack the nontoxic tadpoles.

Strawberry poison dart frog, Costa Rica. Credit, Yannick Ott.

Jennifer L. Stynoski, Yaritbel Torres-Mendoza, Mahmood Sasa-Marin, and Ralph A. Saporito (2014) Evidence of maternal provisioning of alkaloid-based chemical defenses in the strawberry poison frog Oophaga pumilio. Ecology 95(3):587–593.http://dx.doi.org/10.1890/13-0927.1 (open access)

Also in this issue:

Forum—P values and model selection

“Haven’t I seen this before? Do we really need another Forum on P values, hypothesis testing, and model selection?” ask Editor-in Chief of Ecology Don Strong and guest editors in their introductory editorial. Didn’t we go over this in the ’70s? the ‘80s? the ‘90s?

Yes, they conclude, we’ve been here before, but the discussion continues, and statistical hypothesis testing has been taking a beating in the ecological community. Paul Murtaugh, a statistician at Oregon State University, steps forward “In defense of P values.” Seven commentaries accompany his paper, including the Bayesian perspective (Barber and Ogle, “To P or not to P?”). Perry de Valpine’s discussion of “the common sense of P values” is particularly readable.

 [update 24 Mar 2014: read commentary from Caroline Tucker at EBB and Flow on “Debating the p-value in ecology.“

International trade brings foreign species that can have expensive environmental and economic consequences. Establishment in new lands or waters depends critically on the number of immigrants, how quickly they arrive, and the company they keep. Brockerhoff et al present a model to predict future establishments, and conclude that efforts to keep out potential invaders (such as fumigation of wood packaging to kill bark beetles) must be highly effective to be successful.

Eckehard G. Brockerhoff, Mark Kimberley, Andrew M. Liebhold, Robert A. Haack, and Joseph F. Cavey 2014. Predicting how altering propagule pressure changes establishment rates of biological invaders across species pools. Ecology 95:594–601.http://dx.doi.org/10.1890/13-0465.1 (open access)

In the Arctic, cold slows the decomposition of the dead, freezing carbon in leaf litter and other organic debris. But the Arctic is warming, and permafrost is melting. What will be the consequences for ecological communities? Natali et al. experimented with warming air, soil, and permafrost in the northern foothills of the Alaska Range.

Susan M. Natali, Edward A. G. Schuur, Elizabeth E. Webb, Caitlin E. Hicks Pries, and Kathryn G. Crummer (2014) Permafrost degradation stimulates carbon loss from experimentally warmed tundra. Ecology 95:602–608. http://dx.doi.org/10.1890/13-0602.1 (open access)