Honeybee pollination produces plant offspring vastly inferior to plants pollinated by other species

Despite the romanticized image of honeybees, a new study unveils an unexpected truth. Not all bees are equally beneficial for the plant species they pollinate.

San Diego is an area well-known for its diverse flora and fauna. Nestled into its lively landscapes, scientists from the University of California San Diego (UCSD) are revealing intriguing insights into the world of pollinators.

Bees, recognized as key pollinators, are integral to the floral abundance of San Diego. However, the impact varies significantly among different types of bees.

For example, honeybees, foreign to the Americas, produce plant offspring of considerably lower quality than those pollinated by native bees.

How we learned that honeybee pollination is inferior

These findings were detailed in the study recently published in Proceedings of the Royal Society B. They offer a new perspective on the role of honeybees in local biodiversity.

This study is considered a pioneering piece of research that compares offspring quality or ‘fitness’ between plants pollinated by honeybees and those pollinated by other floral visitors.

Earlier research had hinted at the dominance of feral honeybees in San Diego. They account for over 90 percent of pollinators observed around local flowers.

Dillon Travis is a recent graduate from UCSD’s School of Biological Sciences. Travis, along with Professor Joshua Kohn, authored this research.

They have discovered that honeybees visit approximately twice as many flowers on a single plant, compared to native insects, before moving to the next one.

Their meticulous foraging behavior, however, seems to be counterproductive. The reason being, most pollen delivered to the flowers comes from the same individual plant. This is a process known as self-pollination. It often results in lower-quality offspring.

What happens when honeybee pollination dominates a region

To examine the effect of such pollination practices, the researchers conducted a range of experiments. They evaluated the fitness of plant offspring across different factors. These included seed maturation, germination, survival, growth, and reproduction.

The team used three common plant species native to San Diego County for their research. They conducted their work at locations like the Elliott Chaparral and Dawson Los Monos Canyon Reserves under the University of California Natural Reserve System.

The team explored a variety of conditions. These included natural pollination, no pollination, honeybee pollination, native bee pollination, and both self- and cross-hand pollination.

Plants pollinated by native insects produce better offspring

After four to six weeks, they collected seeds from each scenario and compared the fitness of each. Their findings were surprising. Offspring resulting from pollination by native insects, mainly various species of bees, were two to five times more likely to mature, germinate, grow, and reproduce. Thus, they were deemed more ‘fit’ than those resulting from pollination by honeybees.

Professor Kohn, a professor in the Department of Ecology, Behavior, and Evolution, commented, “While honeybees are perceived as beautiful mutualists that are helping plants with reproduction, it turns out they may not be as good for plants as many native pollinators. We have found that they deliver lower quality pollen than do native pollinators.”

Interestingly, honeybees’ tendency to visit more flowers per plant than other pollinators leads to higher levels of self-pollination. This results in lower quality offspring. A related study indicated this pattern was consistent across 44 different plant species. Those included both crop and non-crop plants.

Originating from Europe, Western Asia, and Africa, honeybees were introduced to the Americas in the 17th century. Today, they account for around 13 percent of all global floral visits to native vegetation.

In San Diego, often dubbed as ‘honeybee heaven’, honeybees visit flowers more frequently than nearly anywhere else in the world. The region is also home to over 650 species of native bees and other pollinating insects that interact with at least 2,400 types of plants. That’s more than any other county in the United States.

Honeybee pollination opens the door to invasive species

The researchers worry that honeybees lowering seed fitness of native plants might increase the susceptibility of the native plant community to invasion by introduced plant species that don’t require insect pollination. These are often invasive grasses and other species that contribute to the spread of wildfires.

Travis points out, “People see honeybees as providing a valuable service, which is pollination, but there’s a decent amount of evidence to show that they’re competing with native insects for resources like pollen and nectar.”

Travis also expressed concern over the potential risk of viruses transmitted from honeybees to native bees.

“Many conservation efforts are focused on saving the honeybee, but they are not in any danger of going extinct. In fact, their numbers have been increasing. The organisms that do need our help are the native plants and bees.” he concluded.

These findings challenge us to rethink the role and impact of different pollinators in our ecosystems and conservation efforts.

More about honeybees

Honeybees, known scientifically as the genus “Apis,” are a group of insects famed for their role in pollination and for producing honey and beeswax. Here’s a comprehensive look at honeybees:

Origin and Distribution

Honeybees are native to Europe, Western Asia, and Africa. They have also been introduced to other parts of the world, including North and South America, Australia, and New Zealand. There are several species of honeybees, including the European honeybee (Apis mellifera), which is most commonly kept by beekeepers.

Physical Characteristics

Honeybees are generally about 15 mm long and oval-shaped, with a golden-yellow and brown to black coloration. They have a pair of compound eyes, a pair of antennae, and three simple eyes on the top of the head. Honeybees have two pairs of wings and a stinger.

Social Structure

Honeybees live in colonies housed in hives. Each colony has a single queen, many workers (which are female), and drones (which are male). The queen’s primary role is reproduction. She can lay up to 2000 eggs per day during spring buildup.

Worker bees perform a range of tasks, including foraging for nectar and pollen, making honey, building and repairing the hive, and guarding the colony. Drones’ sole function is to mate with a new queen.

Honey Production

Honeybees make honey from the nectar they collect from flowering plants. Inside the beehive, they use their wings to evaporate water from the nectar, creating honey. The honey is then stored in the honeycomb, which bees make out of beeswax.

Honeybee Pollination

As honeybees go from flower to flower to gather nectar, they spread pollen among the blooms. This pollination is crucial for the fertilization and reproduction of many plants, including a large number of crops that people rely on for food.

Communication

Honeybees use complex communication methods. One of the most notable is the “waggle dance,” which worker bees use to inform others about the location of food sources. They also use pheromones for communication.

Threats

Honeybees face numerous threats, including pesticides, habitat loss, parasites (like the Varroa mite), disease, and climate change. Colony Collapse Disorder (CCD) is a significant problem in some parts of the world, where worker bees suddenly disappear, leaving the queen and a few nurse bees behind.

Conservation

There are various efforts underway to protect and conserve honeybee populations. This includes research into diseases and pests that affect honeybees, breeding programs to create more resilient bees, regulations to reduce pesticide use, and initiatives to plant more wildflowers to provide food for bees.

Honeybee Product

In addition to honey, honeybees produce several other products that humans use. These include beeswax (used in candles, cosmetics, and food), pollen (collected by bees and used as a health food), royal jelly (a food for bee larvae and queens that is also used in health supplements), and propolis (a resinous material used in natural health products).

Beekeeping

Honeybees are kept in beehives by beekeepers, who often provide the bees with a human-made hive. Beekeepers may manage bees to harvest honey and other bee products, to provide pollination services for crops, or for enjoyment.

Remember, while honeybees are beneficial and generally not aggressive, they can and will sting to defend their hive. It’s always important to respect their space and handle them properly if you’re a beekeeper.