Plants and Pollinators: An Overview

Discover the evolution of flowers and bees, while learning how you can bring more diversity and flowers to your garden.


| September/October 2017



Anatomy of a Honey Bee

Anatomy of a honey bee.

Photo by Storey Publishing
When we observe animals pollinating nearly 90 percent of the plant species found on earth, we are witnessing a process more than 250 million years in the making. Sexual reproduction among plants, from a botanical standpoint, is nothing more than the transfer of pollen grains from a flower’s male anthers to a flower’s female stigmas, enabling fertilization. Once transferred, pollen grains germinate, grow pollen tubes into the plant’s ovaries, and deliver gametes to produce seed and endosperm.

In very primitive plants, this process was carried out by wind or water. Between 245 million and 200 million years ago, however, the first flowering plants arose, with the earliest fossil records containing relatives of today’s magnolias and water lilies. During this prehistoric time frame, flowering plants evolved two major reproductive adaptations: exposed male stamens that bear small, nutrient-rich pollen grains; and enclosed female carpels that protect ovules. These adaptations accelerated plant reproduction (and pollinator diversity), leading to diverse and dominant communities of flowering plants that almost 100 million years ago had spread across the globe.

Plants Meet Pollinators

Beetles, flies, and wasps are thought to be the first pollinators, accidentally spreading pollen while feeding on flowers. This set the stage for more complex plant-pollinator relationships to evolve, including prehistoric flowering plants that first attracted passive pollinators by providing sugary nectar, protein-packed -pollen, fragrant resins, and vitamin-rich fats.

Flowers then responded to particular pollinators, co-evolving with them to provide diverse bloom times, colors, scents, shapes, sizes, and rewards, and improving their reproductive efficiency. For example, flattened, large, scented, off-white flowers with accessible pollen, such as magnolia, attracted beetles, while tubular, large, scented, white flowers that bloom at night attracted moths.

Meanwhile, flowers also developed a variety of strategies to avoid self-fertilization and encourage genetic diversity:

  • self-incompatibility
  • physical distance between (male) anthers and (female) stigmas
  • male and female flower structures that are fertile at different times
  • separate male and female plants

Enter the Bees

The widespread distribution of diverse flowering plants 100 million years ago coincided with the appearance of intentional pollinators: bees. Bees are believed to have co-evolved with flowers from predatory wasps. In general, both bees and wasps consume sugars as adults and proteins as larvae. Herbivorous bee larvae eat pollen as their protein source, however, while wasp larvae are typically carnivorous.





elderberry, echinacea, bee hive

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