Beauty and the Bees

Natural History, May, 1999 by David Dilcher

In the beginning, flowers were not much to look at. Fossils of the oldest known flowers, discovered by Chinese researchers last year, reveal that as of 145 million years ago, petals had not yet made an appearance. Possibly these flowers were wind pollinated and had no need to be seen. Or perhaps they were just beginning to lure insects and hadn't yet developed special floral organs to advertise their wares.

What was there to advertise? Their sex organs--or, more precisely, free food. The reproductive success of many flowering plants depends upon their ability to attract animals--which feed on the nectar, and sometimes the pollen, provided by the blossoms--and then to send them off with a dusting of pollen for delivery to the female, pollen-receiving organ of a different flower of the same species. This cross-fertilization, with its resultant mixing of genetic material, was ensured as plants evolved variously shaped floral organs, unique patterns, and chemicals that attracted pollinators.

Showy flowers evolved approximately 125 million years ago. At that time, all petals and reproductive organs were arranged spirally and, from above, would have looked somewhat like the spokes of a wheel. Many contemporary species retain this form. About 90 million years ago, dependable pollinators appeared (most notably bees), and flowers made their next big move evolving new shapes, nectars, and symmetries. The distinctive shapes of the earliest bilaterally symmetrical flowers attracted bees but excluded insects blind to their allure. And only long-tongued bees and lepidopterans could get at the nectar of species with long floral tubes. Such indirect control of the insect's movements made pollination less of a hit-or-miss affair than it was in most radial flowers.

Since that time, flowering plants have increased remarkably in diversity. By about 55 million years ago, nutritious, attractive fruits and seeds became an important part of the reproductive plan of flowering plants. Animals ate the fruits and carried the seeds into new habitats, increasing the probability that

populations would diverge and become new species. Humans, too, have benefited from the coevolution of flowering plants and animals and have further modified the fruits and seeds--even the shapes--of flowers for our own purposes. Their value as food, as well as their beauty and fragrance, enriches and sustains our lives.

David Ditcher ("Up Front") is a graduate research professor at the Florida Museum of Natural History, University of Florida. Much of his current paleobotanical research is conducted in collaboration with Ge Sun, of the Nanjing Institute of Geology and Paleontology.