I think that Colony Collapse Disorder really brought a lot of attention to pollination services, at least in the US, where it is a “hot topic”. It’s hardly a concern in Australia. What about the UK? I don’t know how bees are doing there right now.
In any case, as honeybee populations collapse around the US, managers become more and more interested in the “free” pollination services provided by native communities of bees.
Agapostemon sericeus is a lovely native bee.
Unfortunately, just as we turn to them to fix our problems, we find that their populations are also in decline, albeit for a different reason. In their case, it is the disappearance of worthy habitat. A lot of my research revolves around the question of how best to support communities of native bees, which all comes down to floral resources.
Flowers pay for pollinators, such as bees, with pollen and nectar, which are actively collected by bees for food. Adult bees need nectar (a sweet solution) to provide energy for flying and foraging. They also collect pollen for juvenile bees in the hive. Pollen has nutrients that growing bees need, such as proteins and fats.
Pollinators choose the flowers they like to forage from and can learn not to waste time and energy on certain flowers if they don’t provide rewards.
“A bee in a meadow with many different flowers faces a task not unlike that confronting an illiterate shopper pushing a cart down the aisle of a supermarket. Directly or indirectly, both try to get the most value for their money. Neither knows beforehand the precise contents of the packages on the shelf…But they learn by experience.” Bumblebee Economics, Heinrich 1979
Flowering plants also need pollinators because bees can carry pollen and can thus cause the fertilization of seeds (that’s why it is called a mutualism). Because pollinators are so important to the reproduction of most flowering plants, they compete with each other to attract the attention of picky pollinators.
There is a book, in fact, which details the costs and rewards of foraging for bumblebees. It’s called Bumblebee Economics by Bernd Heinrich. It is an excellent book, and fascinating. Heinrich is another one of my academic crushes. He’s published on topics as widely varying as being beetlized and cuckoos.
From a foraging theory perspective, bumblebees are especially interesting because they regulate their body temperature in a pseudo-endothermic way. Which is to say, they are not actually endotherms (being insects), but they can control their body temperature through a marvelously elegant system of counter current exchange between their abdomen and thorax. They also can shiver the flight muscles in their thorax to generate heat. All this means that they can forage in much cooler temperatures than other types of bees.
Bumblebee absolutely covered in thistle pollen.
Which is why they are so important in alpine and high latitude floral communities, where they provide the majority of pollination services.
Sleepy bumblebee in Colorado.
Anyway, back to the plants. Which species are the best for pollinators? One of the primary challenges is quantifying the floral resources. I’ve done pollen counts using imaging software (it’s kind of cool to look at pollen grains under a microscope). I’ve also taken samples of nectar from the flowers and compared the different volumes provided.
I mentored a group of high school students during the summer. For part of our project, I taught them how to measure nectar. Here is one of my students collecting nectar from a sunflower in the greenhouse.
One thing that I quickly learned is that it is not as simple as I had originally thought. This realization keeps happening to me, in a multitude of different situations and circumstances. Epiphany: nothing is simple.
As it turns out nectar is not just sugar water…it also provides critical micronutrients to the bees. And the dimensions on which its quality varies are many: concentration, quantity, presence of glucose vs. fructose, amount of micronutrients, etc. It is more like Gatorade than sugar water, in fact.
Conclusion? Supporting native bees is complicated, but I’m convinced that we can figure it out. Maybe I’ll get a PhD out of the deal.
Nectar from the extrafloral nectaries of Partridge Pea (Chamaecrista fasciculata). We collect it using microcapillary tubes. Nectar is drawn up into the tube via capillary action (cohesive forces within the liquid).