A quote from above: “The truth is that many if not most native bees are plant-specific in their foraging preference.”

On the contrary, most native bees are polylectic, foraging from many plant species just like honey bees. While some bees in the family Andrenidae forage on one species alone (especially bees in the genera Andrena and Perdita) most bees that specialize are restricted to a plant family (such as Asteraceae) not a single species.

True monolectic foraging (one specific bee on one specific plant) is extremely rare, which is good news because monolectic bees can easily starve to death in areas of heavy competition. Polylectic bees have more choice, so they can do better.

“Global warming is causing their specific forage plant to move up to a higher elevation or latitude, but the native bee cannot move up due to other environmental needs it has (such as nesting
sites or water sources).”

This phenomena, attributed to global warming, has been documented on rare occasions. It is called a climate vise, and forms because the bees lose preferred forage in the southern portion of their range, but do not move north along with the forage plants. Their foraging range becomes constricted.

But a climate vise does not eliminate competition from other bees. In fact, it may increase it because the desirable habitat area becomes smaller. You can’t assume that bees in a climate vise have only one problem. 

“It's common to see popular confusion about native bee decline vs honeybee decline.”

Agreed. I always wonder about the distinction between “native bees” and “honey bees.” Why aren’t we talking about the rest of them, the roughly 60 introduced species in North America? How do they fit into the equation?

Introduced species come in many forms, including deliberately introduced species like Apis mellifera, Osmia cornifrons, Osmia taurus, and Megachile rotundata. They come accidentally via shipments, especially the cavity nesters such as Anthidium manicatum, Anthidium oblongatum, and Megachile sculpturalis. Some arrive in the soil of potted plants like Andrena wilkella. Others are adventive, arriving due to expanding ranges, such as Euglossa dilemma down in Florida. 

Many of the introductions run rampant because, like introduced plants, they have few natural enemies in their new land. These bees are not necessarily good or bad, but they can’t be ignored because they, too, compete for resources. The honey bee vs native bee argument makes no sense because it disregards too many species.

To say there is no competition between honey bees and other bees is also ridiculous: you always have competition when individuals share resources. But to say honey bees cause native bee decline is a stretch because there are too many confounding variables to easily sort it out. Studies go one way or the other depending on protocols, and nothing is clear.

Like many melittologists, I believe the main factor in bee decline is competition from humans and all we bring to the table, things like habitat fragmentation, habitat loss, pesticides, pollution, climate change, pathogen introductions, or whatever. But what is their relative importance? Who knows. Our obligation is not to point fingers at other species, but to find answers to common bee problems.

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