A study documents evidence for an orchid fossil trapped in Baltic amber dating back 45-55 million years ago, breaking the record of 20-30 million years in Dominican amber.
The orchid family has about 28,000 species – more than twice the number of bird species and four times the number of mammalian species. Of course, they have been on Earth for a long time.
“It wasn’t until just a few years ago that we had evidence of ancient orchids because there was nothing preserved in the fossil record,” George Poinar, Jr., emeritus professor of entomology at the Oregon State University College of Sciences, said in a statement. and lead author on the study, published in the Botanical Journal of the Linnean Society.
“But now we are beginning to find evidence of pollen associated with insects trapped in amber, opening the door to some new discoveries.” Orchids have their pollen in small sac-like structures called pollinia, which are attached by supports to viscidia, or sticky pads, that can adhere to the various body parts of pollinating insects, including bees, beetles, flies, and mosquitoes. The entire pollination unit is known as a polinary.
In this study, a small female fungus gnat carried the polinaria of an extinct species of orchid when it was trapped in amber more than 45 million years ago. The polinaria was attached to the base of the mosquito’s hind leg. Amber preserves fossils so well that the researchers were able to identify a frozen blood droplet on the tip of the mosquito’s leg, which had broken shortly before it was entombed in amber.
At that time, all the continents had yet to distance themselves. The fossil shows that orchids were well established in the Eocene and it is likely that the lineages extended back to the Cretaceous period. Until such forms are discovered, the present specimen provides a minimal date that can be used in future studies determining the evolutionary history and phylogeny of orchids.
How the orchid pollen in this study ended up attached to the fungus gnat and eventually entombed in amber near the Baltic Sea in northern Europe is a matter of speculation. But, Poinar says, orchids have developed a surprisingly sophisticated system for attracting pollinating insects, which may have led to the mosquito’s demise.
“We probably shouldn’t say this about a plant,” Poinar joked, “but orchids are very smart, they have developed ways to attract small flies, and most of the rewards they offer are based on deception.”
Orchids use the color, smell, and charm of nectar to attract potential pollinating insects. Orchids give off an odor that suggests the promise of food to hungry insects, but after entering the flower they will realize that the promise of food was false.
Likewise, females can pick up a fungal odor from many orchids, attracting them as a place to lay their eggs because decaying fungal tissue is a source of future nutrition. Unfortunately, it is a ruse again. In frustration, they can go ahead and lay their eggs, condemning their offspring to probable death from lack of food.
Eventually, male insects are attracted to the scent of female flies and will actually attempt to copulate with a part of the orchid that they think is a potential mate. All three of these processes are based on deception, Poinar said, and they all have the same end result.
“Although the deception works in different ways, the bottom line is that the orchid is able to attract pollinating insects, which involuntarily collect pollen that sticks to its legs and other parts of the body, and then move onto the flowers of other orchids. “, said.