A renowned orchid expert recently showed a group of Selby Gardens staff, volunteers and guests examples of how advances in genetics have expanded our understanding of orchids—their origin, their specialization and relationships between various orchid species.
Dr. Mark W. Chase, a senior scientist specializing in orchids at Royal Botanic Gardens, Kew, noted that orchids are related to plants in the order Asparagales, which includes daffodils, century plants, hyacinth, iris and asparagus.
“The big question is, how do you get something that looks like an orchid flower from something that looks like a hyacinth flower, which has six equally-shaped parts? Orchids are very different looking,” Chase said. “Orchids are characterized by having one petal turned into a lip, and that is quite an unusual structure. It has always been a question as to how this has come about. Why is one petal so different from the others?”
Chase explained that researchers now know the genetic basis for that difference. There are floral genes that control the flower shape. In most plants, such as the hyacinth, there is just one, which makes the petals look the same. In orchids a duplication of a gene creates the lip. Various combinations of genes and the duplication of some give the orchid flower the great capacity to have different shapes.
Chase discussed the importance of the orchid lip to the orchid’s ability to attract pollinators. “The capacity of the orchid to change its floral shape makes it more adaptable to a variety of pollinators than other plants, “he said. “The ability to make a petal differently shaped allows the orchid to specialize in pollinators in a way other types of plants could not possibly do.
“All of the orchid flower is designed to be seen by insect eyes,” he added. “So in some cases what looks to us to be very ugly may be to the insect very beautiful.”
He cited the fly orchid (Ophrys insectifera) found the United Kingdom and other parts of Europe. This orchid fascinated Charles Darwin, who said its flower looked like a wasp or fly. The insect thinks so too, and the male thinks it looks like the female of its species. It’s attracted by the shape and color of the lip and the smell it emits, which mimics the insects’ sex pheromones.
“So it looks and smells like a female wasp. The wasp tries to consummate the relationship but it’s a failure because it’s not a wasp, it’s a plant. But it fools the wasp very effectively. It’s a waste of his energy.”
Chase also cited orchids found in Central and South America called Coryanthes speciosa. This bucket orchid collects liquid in the bucket, the highly modified lip. Special glands on the flower produce a scent that attracts bees, which fall into the bucket and carry the flower’s pollen on their way out. “There is no other group of plants with this type of pollination where the insect falls into liquid and has to climb out,” he said.
Genetic sequencing has determined that orchids are one of the oldest families of flowering plants, dating back more than 100 million years, Chase said. Previously it was thought that orchids developed much later in time because until recently very few orchid fossils had been found.
But using a molecular clock that is based on changes in DNA sequences, it was determined that orchids date back 110 million years. Since then, researchers have found more orchid fossils.
“People are now finding orchid fossils because they are looking at older rocks,” Chase said, explaining why such fossils were not found previously. “It’s human nature…we get an idea of what we are looking for and we tend to disregard the things around the edges. Now we find fossils that go back 35 or 45 million years because we are adjusting the search to look for orchids in rocks we previously wouldn’t have looked at. “
The specialization within the orchid family—there are 26,800 species with 200 new ones discovered each year– is a product of the amount of time they’ve had to become specialized, Chase added.
Chase interrupted his vacation in St. Petersburg to speak at Selby Gardens at the request of long-time friend Dr. Antonio Toscano de Brito, head of Selby’s Orchid Research Center, with whom he has collaborated on several projects. A senior researcher at Royal Botanic Gardens since 1992, Chase has published more than 500 research papers and eight books. He recently co-authored Plants of the World: An Illustrated Encyclopedia of Vascular Plant Families (Kew Publishing and University of Chicago Press, 2017), which he described as a “complete photographic encyclopedia” of plants.