Tuesday, November 22, 2011

The Arms Race in Dendrobatid Frogs

Shape dough into frogs, that's normal in a day care. At university, it is more rare. However, the biologist Mathieu Chouteau in 3600 he made a carefully painted as part of his Ph.D. project in the Department of Biological Sciences at the University of Montreal. A month of work to which his wife had worked closely.

He then divided this bestiary in sites previously identified in the middle of the Amazon rainforest. "The hardest part was carrying my models without arousing suspicion at the airport and customs controls," says Mathieu Chouteau in an interview from Peru, where he pursued a fellowship in collaboration with the National Museum of Natural History of Paris.

In an article to be published in December in Natural History that has already been the subject of a new site ScienceNOW (Helen Fields, "Why Are There So Many Colors of Poisonous Frogs", November 4, 2011), he concludes that the Predation is a natural selection factor in the development of multiple motifs in the species Ranitomeya imitator, a frog under a centimeter in various colors. The models on clay he has documented fact in the evolution of colors and patterns of dendrobates: the role of predators.

As we learned from our first visit to the Montreal Biodome, brightly colored frogs which can be seen in the rain forests launched a clear message to predators: do not approach me because I am poisoned! But why is it some green with a pattern of leopard and other yellow lines while in the same species? Presumably because predators taste the local people they do not associate with frogs in the area, hoping that these frogs are edible. "When predators are they are dealing with a different species, they attack. In the long term, this would explain the unity of the patterns and colors, "says Bernard Angers, who led the research of Mr. Chouteau.

The methodology is rather original. Three times for three days at two sites, Mathieu Chouteau noted his false attacks on frogs - mostly pecking. The least attacked were those most closely resembles the native species, while those who were most distant showed signs of aggression. He had more than 300 fake frogs per site.

Seeing that no food, some predators attacked plasticine frog.

Why play dough to observe predation? The doc had this idea by browsing the scientific literature. "We have successfully used models in clay for snakes, salamanders and also dendrobates," said Mathieu Chouteau. It was in the Peruvian jungle terrain ideal for testing the hypothesis, as two radically different colonies of frogs have been studied: one attending the plain is dotted with green and the other on top of a mountain is yellow line ... The two settlements are separated by about 10 km. False frogs were deposited in two sites in specific locations. As for colors and patterns, they differed in several combinations.

What was most surprising in this research is "the very small spatial scale at which evolutionary processes occur." In the case of Dendrobates, a distance of 10 km is sufficient to demonstrate an adaptation clearly different. "A second surprise has been the learning capacity of the communities of predators, but also the speed with which this process begins when a new aposematic signal is massively introduced exotic," said the biologist.

"We have proved empirically that avian predators can recognize and avoid aposematic signals in various sites," he wrote in conclusion of his article.

This process could be the cause of the wide variety of color patterns observed not only in frogs but also among many species of butterflies and bees and other animals. The purpose of the postdoctoral fellowship is also to explain the polymorphism in the butterfly genus Heliconius. "Given that such a project request to be on the ground regularly, I settled in the small town of Tarapoto , where I am responsible for implementing a research center to facilitate studies of mimetic neotropical butterflies, "he says via email.

Bernard Angers admiration for his student, especially as this research is only one of four components of his doctorate. Patience, creativity and discipline were to converge to implement such a protocol. It also highlights the qualities of photographer Mathieu Chouteau (including readers of Forum can get an idea on page 1).

If they are of great beauty, dendrobates are among the most toxic animals on the planet. The student has experienced when, after a hard day's work Cainarachi, it has not taken the time to wash their hands before snack. "Error! Approximately five minutes after starting to eat, I had the lips and throat stung and it ended with a serious food poisoning that lasted two days, "he recounts.

Mathieu-Robert Sauvé

No comments:

Post a Comment