Data from a University of Vermont researcher is helping the U.S. Fish and Wildlife Service make the case that the rusty patched bumblebee should go on the national endangered species list.
The native bee has seemingly disappeared from Vermont; it was listed as endangered in the state last year.
The rusty patched bumblebee was once quite common across the upper Midwest and eastern Northern America, including in Vermont. But since the mid-1990s, there's been a precipitous crash in population.
Leif Richardson is a post-doctoral researcher with UVM's Gund Institute who studies the relationship between bees and the plants they pollinate.
Using samples from museums and collectors across the country, Richardson created a comprehensive database, documenting thousands of bumble bees that were collected over the 20th century.
"In the case of this one, the rusty patched bumble bee, we found lots of specimens of this bee over the years, until about 1995," says Richardson. "And then they abruptly disappear from collections."
Richardson says when scientists realized the bee was suddenly not around, they intensified their search for it-— but still found hardly any rusty patched bumble bees in the last 15 years. None have been identified in Vermont since specimens found in Huntington in 1999.
U.S. Fish and Wildlife officials expect they will make a decision as to whether to officially list the species as endangered by this time next year.
Researchers believe the decline stems from a number of factors, including habitat loss, pesticide use, climate change and bee pathogens and parasites.
"This bumble bee was once very common in Vermont and other parts of the eastern United States and southern Canada," says Richardson. "It has become extinct locally in many places, and hangs on just in a few spots in the northern Midwestern states."
A ripple effect throughout the ecosystem
Richardson says the wild bee was playing a substantial role as a pollinator of many crop plants including blueberries, apples, tomatoes and eggplant.
In addition, "the rusty patched bumble bee has associations with a number of native plants that are important parts of our ecosystems," he says. "And so when lose a pollinator that is important to plants, we may see changes in plant community structure, we may see a loss of biological diversity."
While the decline of the rusty patched bumble bee does parallel other losses seen across the country, it is considered a separate issue from the colony collapse disorder that's affecting introduced European honeybees.
Richardson says some other native bumble bee species that are similar to the rusty patched bee have also declined, including the yellow-banded bumblebee, which is listed as threatened in Vermont, and Bombus ashtoni, a kind of cuckoo bumble bee, which is listed as endangered in Vermont.
In addition to habitat loss and pesticide use, some scientists have suggested that pathogens spread from bee to bee at the flower could be killing off the bumble bees. Richardson likens it to "when you catch a cold from somebody when you touch a door knob that they just touched."
Some scientists suspect the Nosema bombi fungus, which may have come over from Europe, could be one of the culprits.
Richardson isn't working directly on the research into Nosema bombi, but he says the overall challenge underscores the importance of museums and specimen collections in painting an accurate picture of how bee populations are changing over time.
"This is the best we have to go on, this museum specimen data, because nobody was actually doing standardized surveys earlier in the 20th century," says Richardson.
"In many places in the U.S. and elsewhere, museums and these old musty collections of plants and insects and mammals and other things are under threat because they're losing funding," he adds. "But what we've done here is shown that bee specimens collected 75 or 100 years ago actual have value for conservation."