Using a 3D printer, scientists have unlocked the mystery of how plants called Dracula orchids use mimicry to attract flies and ensure their survival.
The research, done in the last unlogged watershed in western Ecuador, is a win in the field of evolutionary biology and helps provide information that should benefit conservation efforts. The approach could also be applicable to studies of other plant-pollinator systems, researchers say.
Tobias Policha: The view of the fly
“Mimicry is one of the best examples of natural selection that we have,” says Barbara “Bitty” Roy, a biologist at the University of Oregon. “How mimicry evolves is a big question in evolutionary biology. In this case, there are about 150 species of these orchids. How are they pollinated? What sorts of connections are there? It’s a case where these orchids plug into an entire endangered system.”
Dracula orchids grow in Central America and northwest reaches of the Andes Mountains in South America. The Dracula label literally means “little dragon” because of a face-like feature in the flowers. Some observers say they see Count Dracula as a bat that appears in vampire depictions in literature and the movies.
“Dracula orchids look and smell like mushrooms,” says Tobias Policha, an adjunct instructor and plant scientist in the Institute of Ecology and Evolution and lead author of the study that is published online in the journal New Phytologist. “We wanted to understand what it is about the flowers that is attractive to these mushroom-visiting flies.”
The researchers closely studied 22 orchids, looking piece-by-piece, to determine where specific scents are produced in the flowers and which ones possibly lure pollinators—in this case 11 species of fruit flies that thrive among wild mushrooms that grow near the orchids.
To test their work in the forest, they turned to odor-free, silicone copies of orchids made with a 3D printer.
The 3D copies—the same shape and size of real ones—allowed the researchers to apply various color patterns and extracts of the various scents. Among the mix of experiments they also used chimeras—3D copies with real and artificial parts—that allowed them to disentangle which parts were attractive. Flies were drawn to the fabricated plants as if they were real.
The findings show that the key part of the orchids’ mimicry is the mushroom-like labellum, which is attached to the plant’s narrow reproductive column.
“What the orchid wants the fly to do when it arrives is to crawl into the column, whereupon the orchid sticks a pollinium onto the fly so that the fly can’t possibly get it off,” Roy says. “The fly then goes to another orchid, which then pulls it off.”
A pollinium is gooey package, resembling a saddlebag, and contains an orchid’s pollen. Flies spend up to an hour inside the plant’s reproductive column, which is a snug fit to a select few of the more than 80 species of drosophilid flies that have been identified so far in the area.
Other researchers from the University of Oregon, Cornell University, and Aberystwyth University are coauthors of the study. The 3D versions were made by coauthor Melinda Barnadas, co-owner of Magpie Studio, which fabricates scientific artwork for museums. The National Geographic Society and National Science Foundation supported the work.
Source: University of Oregon