Honeybees Found to Be Less Effective Pollinators Than Native Species

Originally native to Eurasia and Africa, honeybees were brought to North America in the 17th century, according to Phys.org. For centuries, they flourished, until colony collapse disorder, along with habitat loss, pesticide use, diseases, invasive species and climate change caused their numbers to decline.

In a new study, Dillon J. Travis and Joshua R. Kohn, two University of California, San Diego, ecologists, have found that native pollinators are better at pollinating flowers than honeybees.

“Here we show that, for three common native self-compatible plants in Southern California, super-abundant, non-native honeybees (Apis mellifera L.) visit more flowers on an individual before moving to the next plant compared with the suite of native insect visitors. This probably increases the transfer of self-pollen. Offspring produced after honeybee pollination have similar fitness to those resulting from hand self-pollination and both are far less fit than those produced after pollination by native insects or by cross-pollination,” the researchers wrote in the study.

The study, “Honeybees (Apis mellifera) decrease the fitness of plants they pollinate,” was published in the journal Proceedings of the Royal Society B.

In their research, the scientists compared wildflower samples that were pollinated by various types of pollinators, including butterflies, moths, honeybees and other bee species, reported Phys.org.

The researchers sat outside in fields in the San Diego area waiting for flowers to be pollinated. They limited the types of flowers they used for the study to three: Phacelia distans, black sage (Salvia mellifera) and white sage (Salvia apiana).

According to an earlier study, in San Diego County, California, wild Western honeybees are responsible for 75 percent of all pollinator visits to flowers.

The researchers in the recent study collected plant seeds that had been visited by pollinators and planted them to see how well they would grow, Phys.org reported. They also pollinated some seeds themselves.

They discovered that honeybees were not only the most frequent visitors to the flowers, but that the P. distans and white sage they had pollinated only produced about 50 percent of the seeds as those that had been pollinated by native species.

In addition, they found that P. distans grown from honeybee-pollinated seeds had fewer flowers than the plants pollinated by native pollinators.

An explanation for the seeds’ low quality could be that honeybees had a tendency to visit more flowers on an individual plant than native pollinators, which can cause inbreeding.

The offspring of plants pollinated by native species had a two to five times higher likelihood of surviving and reproducing than plants that had been pollinated by honeybees, reported New Scientist.

There are 2,400 plant species and more than 600 native bee species in San Diego County, but the effect of honeybees on this flourishing ecosystem isn’t known, said Kohn.

“If native plant fitness is reduced, there’s more open space for invasives,” Kohn said, as New Scientist reported.