Amber-preserved stingless bee carrying pollinia
of Meliorchis caribea, the first unambiguous
fossil orchid known to science.
This discovery enabled researchers to calculate
the time of origin of the orchid family.
(Credit: Santiago Ramírez)
First Orchid Fossil Puts Showy Blooms At Some 80 Million Years Old
ScienceDaily
(Aug. 30, 2007) —
Biologists at Harvard University have identified the ancient fossilized remains of a pollen-bearing bee as the
first hint of orchids in the fossil record, a find they say suggests orchids are old enough to have co-existed
with dinosaurs.
Their analysis, published recently in the journal Nature, indicates orchids arose some 76 to 84 million years ago, much longer ago than many scientists had estimated. The extinct bee they studied, preserved in amber with a mass of orchid pollen on its back, represents some of the only direct evidence of pollination in the fossil record.
"Since the time of Darwin, evolutionary biologists have been fascinated with orchids' spectacular adaptations for insect pollination," says lead author Santiago R. Ramírez, a researcher in Harvard's Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology. "But while orchids are the largest and most diverse plant family on Earth, they have been absent from the fossil record."
The fossil record lacks evidence of orchids, Ramírez says, because they bloom infrequently and are concentrated
in tropical areas where heat and humidity prevent fossilization. Their pollen is dispersed only by animals, not wind, and disintegrates upon contact with the acid used to extract pollen from rocks.
Orchids' ambiguous fossil record has fed a longstanding debate over their age, with various scientists pegging the family at anywhere from 26 to 112 million years old. Those arguing for a younger age have often pointed to the lack of a meaningful fossil record as evidence of the family's youth, along with the highly specialized flowers' need for a well-developed array of existing pollinators to survive. Proponents of an older age for orchids had cited their ubiquity around the world, their close evolutionary kinship with the ancient asparagus family, and their bewildering diversity: Some 20,000 to 30,000 species strong, the showy plants comprise some 8 percent of all flowering species worldwide.
