When Michael Orr, a graduate student at Utah State University, observed what appeared to be bee nests in sandstone at the Grand Staircase-Escalante National Park in Utah, he decided to investigate by examining bee specimens at the USDA’s National Pollinating Insects Collection. Rummaging through drawer after drawer, he finally found what he’d been seeking: specimens of an unnamed, fuzzy, gray bee and their nests, which were carved into chunks of sandstone.
Intrigued, Orr contacted Frank Parker, a retired federal researcher who found the specimens 40 years ago, to confirm the drawer’s contents.
“The nests remained a mystery until I got back to the lab and discussed the holes with Frank Parker, who had coincidentally first found this species nesting in sandstone in Goblin Valley almost four decades ago but never published on it,” Orr said. “So it’s actually a pretty interesting story of rediscovering and publishing lost science. We worked together a lot to piece together the whole story.”
Orr then devised a plan to learn more by piecing together clues about the bee’s identity and nesting behavior from sites in seven southwestern states, including Puebloan cliff dwellings at Mesa Verde National Park in Colorado.
In the journal Current Biology, Orr and his colleagues reported their findings about the strange but tenacious sandstone bee. They named it Anthophora pueblo in recognition of ancestral Puebloans who skillfully built their dwellings in cave entrances and cliff faces more than 700 years ago, mainly in what is now the Four Corners region consisting of Utah, Colorado, New Mexico, and Arizona.
The researchers conducted laboratory and field work to expand on what Parker could tell them about the 10-15 mm long native bee, which uses its powerful mandibles and water to tunnel into certain types of soft sandstone rock on cliff sides and walls.
Among the team’s findings:
– The bee’s investment in time and energy — including wear and tear on its mandibles — is well worth the protection it gains from nest-invading beetles, predators, pathogens and even flash floods.
– Generations of A. pueblo bees will inhabit and even add to the nest tunnels begun by forebearers, with thousands of tunnel entrances sometimes pitting the rock face.
– The durable nature of the sandstone nests allows young bees to stay put for a few years, and they emerge only when flower blooms are at their peak — a behavior the researchers call “bet-hedging.”
These and other survival tricks make A. pueblo an interesting generalist pollinator and important contributor to the health of southwestern desert ecosystems. But the species’ preference for sandstone nesting habitat may preclude its managed use in large-scale crop production areas where honey bees or certain types of bumble bees are typically used.
“There are now, in total, six out of 20,000 bee species worldwide known to excavate sandstone nests,” Orr said. “Quite a rare behavior!”
In the future, he hopes to study the genetic interrelatedness of sandstone communities to see if they comprise separate populations or work together as “one big happy family.”
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