According to new research published in the journal Ecology, specific flower characteristics have a bearing on bumble bee health by controlling the spread of the dangerous pathogen called Crithidia bombi. The University of Massachusetts Amherst research, in particular, demonstrates how the length of a flower’s corolla, or flower’s petals, affects how this pathogen spreads among bees because shorter corollas mean that fewer bee feces wind up inside the flower itself and in the path of the bees seeking nectar.
Recent scientific warnings about the “insect apocalypse,” or widespread extinction of the world’s bugs, have been issued. According to some estimates, the insect population of the planet has decreased by 75% over the previous 50 years. The decline of pollinator species, some of which scientists estimate have died back by 90% in the US over the previous twenty years, is one of the numerous ecological repercussions of this holocaust.
Although there are other causes for the end of the world, such as habitat loss, the misuse of pesticides, and others, one factor is the destruction caused by diseases. A common affliction affecting bumble bees is a parasite known as Crithidia bombi, which is frequently spread by bee excrement.
Planting pollinator gardens has been a well-known and successful initiative to conserve bees. But what kinds of plants should we be growing? asks Jenny Van Wyk, the principal author of the study and a postdoctoral researcher in biology at the University of Massachusetts Amherst. “In order to think beyond knowledge that is exclusive to a single species, we are aiming to collect data on how floral features affect pollinator health.” By doing so, we might be able to make generalizations about species that share comparable features and, hence, inform planting choices.
Particularly, shorter-petalled blooms of the same species may be less likely to spread diseases than flowers with longer petals.
This is due to the fact that bees delve deep into blooms in search of nectar. A bee may be able to fit its complete body inside lengthy petals. The next bee that visits the bloom in search of nectar and pollen will end up covered in another bee’s poop since the defecating bee’s feces are left inside the blossom. The second bee would be highly susceptible to infection if the dung turned out to contain Crithidia bombi.
Van Wyk claims that bees’ bottoms hang out in shorter-petaled flowers, where their feces harmlessly fall to the ground.
Van Wyk and her colleagues used an army of UMass Amherst graduate and undergraduate students to plant native wildflower areas that were protected by tents in order to come to this conclusion. In these tents, bumble bees were left unattended. Van Wyk and her colleagues dyed the half of the bees that were healthy blue to make identification easier. The other half received Crithidia bombi vaccinations.
To determine which characteristic had the most impact on bee health, the researchers then changed the morphological characteristics of the flowers in each tent. Van Wyk and her team cut approximately 105,000 flowers with small scissors to measure the length of the corollas. The researchers placed some flowers on the plant in a cross-like arrangement and others in a more linear shape to see if the orientation of the blooms on the plant had an impact.
Additionally, they investigated if the availability and dispersion of nectar affected bee health. The team tested whether the amount of nectar per flower played a role by inserting a tiny, nectar-filled pipette into more than 6,500 flowers and squirting more of the sweet substance. They also sprayed entire groups of plants with sugar water to see whether the distribution of nectar had an impact on bee health. Finally, the team contrasted plantings of blooming plants that were closely packed together with those that were spread out.
Van Wyk and her colleagues gave the bees fluorescent paint in order to identify where the bees’ waste fell. They used a black light to find the glowing poop to determine where the infection had been dumped.
After all of this, the scientists discovered that disease transmission was decreased by trimming the corolla lips, equally distributing nectar throughout a group of flowers, and planting flowers farther apart. More larvae were produced in flowers with clipped corollas and in plant patches where nectar was more evenly distributed.
Only a few studies have compared the ability of flowers from various species to transmit bee diseases, and only one study, published more than 25 years ago, manipulated a floral trait to determine its causal role in disease transmission, according to Lynn Adler, professor of biology at UMass Amherst and the paper’s senior author. “Our research reveals that a variety of characteristics may be significant.”
“What should I plant for bees?” is the most frequently asked question, according to Van Wyk, when he gives public lectures. “Our findings pave the way for additional investigations into the physical floral traits that support bee health, which can guide management strategies.”
The National Institutes of Health funded this research.
