Fascinating Native Bumblebees

 

Bombus sonorus- Summertime bumblebee in San Diego

While everyone is aware of, and recognizes, a common European honeybee, most people wouldn't be able to recognize a native bee. A good reason for this is because they come in a large variety of shapes and sizes, ranging from barely visible to large glossy black carpenter bees. It is very likely that a wide variety of native bees are already in your garden.

While carpenter bees fly past very visibly, most of the others zip past with little fanfare and a great deal of haste, as they have little time to waste. From the time they emerge from their cocoons the females are devoted to one thing and one thing only, the building and provisioning of their nests. The males, on the other hand, have nothing to do but mate with as many females as possible, and to fight off other males trying to do the same thing. Anything that keeps this from happening reduces their chances of passing on their genes to the next generation. They are set on maximizing their reproduction.

Tiny Halictus bee on a California Poppy                                    Photo by Don 0wens

A novel way native bees can speed things up is by "traplining". This is a remarkably clever foraging strategy that seems impossible in such a small creature as the bumblebee. Bees instinctually know to visit flowers for pollen, as nest food, and for nectar, for their own energy needs. After finding the flowers, they must prioritize them according to the floral reward each individual patch of flowers provide. In just a few trips, bumblebees will sort out the most efficient route from their circuit of flowers back to the nest. Keep in mind this keeps changing as plants go in and out of bloom. Bees are traplining when they visit flower patches in a stable and repeatable sequence. It is remarkable to me that these tiny brains can do such incredible feats.

To avoid wasting precious time bumblebees also practice "floral constancy." Meaning that they will spend more time on one species of flowers or species with similar floral characteristics or morphologies. By concentrating only on similar floral structures the process and handling is as close to the same with each flower as possible. Using this method greatly speeds up how fast bees gather pollen. Different flower species vary wildly in their floral structure and where (or if) they have pollen. You can imagine using floral constancy as a foraging strategy is a powerful tool for the bees. It also allows other bees to concentrate on other floral forms so all the available flowers are used and pollinated most efficiently. Is that cool or what?

Buzz Pollination

Possibly the most fascinating time-saving trick used by bumblebees is called "buzz-pollination" or sonication. There are approximately 24,000 species of plants in different plant families that make it difficult for bees to get the pollen. You are familiar with at least a couple of the plants if you eat potatoes and tomatoes from the Solanaceae Family. The Solanaceae Family is unique in that the pollen is hidden in poricidal anthers. Normally, the pollen from plants is prominently displayed and easily accessible to pollinators on the distal end of anthers. Bumblebees have figured out a fast and efficient way to gather the hidden pollen in poricidal anthers. Imagine a tube with holes on the ends and pollen inside. This is roughly the shape and structure of a poricidal anther. Bumblebees land on the tubular anther, bite the end, and grasp it firmly with their clawed feet. To access the pollen they disengage their flight muscles and vibrate them at a higher frequency, the force of the frequency forcibly expels the pollen, and dumps it all over the bee. When you listen to this happening in the garden the normal buzzing is interrupted by a high-pitched whine when the bee is sonicating. The magic frequency is about 270 Hz, “equivalent to a C-sharp above middle C on the piano.” Sonication allows the bumblebee to pollinate much faster than normal. 

This is a small snapshot into the wonderful world of native bumblebees, and it is by no means exhaustive. I have plenty to share. Please take care of the bees that visit the flowers in your garden. Consider planting native plants and minimizing pesticide use to increase the chances you will see more of these wondrous creatures in years to come.

Gardening for Wildlife

                                           Gardening for Wildlife

It is easy to fall in love with flowers. Once I figured out I can have flowers, birds, butterflies, lizards, and so much more I was hooked. Inviting wildlife into the garden suddenly makes gardening come alive with sound, movement, and activity. No longer just looking at flowers, but now participating in fostering growth and health - creating an ecosystem! 

Bombus vosnesenskii on Verbena lilacina                                                                  S.Reeve

Few places possess the biological richness of our home in San Diego County. In fact, San Diego is deemed a “Biological Hotspot” because of the high species richness that is unparalleled in the continental United States. One way we can help protect the large number of unique species is to landscape our homes with native plants. Think about it. Millions of years have honed the relationships between the endemic flora and fauna to the perfection that exists today. 

Sphaeralcea ambigua                                                                                            S. Reeve

Look around - what plants do you commonly see in your community? That’s right, just a small number of exotic plant species that seldom feed any wildlife exist in most gardens. The nectar from that tropical hibiscus or rosemary is not nearly as nutritious for local hummingbirds and bees as is the nectar produced by natively occurring Salvia mellifera or Phacelia campanularia. Local plants offer optimal nutrition for local fauna. Not only that, but exotic species are often poisonous to our fauna. For example, Nandina berries, although eaten by local birds, may kill them if consumed to excess. An opposite example of this is between our native Aesculus californica and honeybees--an exclusive diet of pollen and nectar from this plant will kill or disfigure the progeny of the honeybee. Honeybees are not from San Diego they originated in Europe and did not evolve to partake of our native Bottlebrush. Let’s give our local fauna the local plants that offer them the chance to thrive.

Ribes speciosum                                                                                                     S. Reeve

But, you say, my Pyracantha has fruit that the birds relish. That may be true, but recent studies show that not only is the nutrition superior in local plants, but the phenology or timing of the plants makes all the difference to the reproductive success of the creatures that evolved to eat the plants. Meaning that even though a species of bird will consume fruit from non-native plant species their reproductive fitness is decreased just enough to negatively affect the birth rate. Both the timing of the crop and the nutrition of non-natives are inferior to the native species.

So we have the excellent nutrition native plants provide, plus native endemic plants are drought tolerant. In San Diego we typically get less than a foot of rain a year, and all of it in the months of winter and spring. Native plants have evolved adaptations to be able to survive on little water in the colder months and no water in the summer. Better yet, using locally sourced native plants fine-tunes the drought tolerance to the same conditions as exist in your garden at home. That means little-to-no supplementary water, even in the summertime.

Salvia spathacea                                                                                                    S. Reeve

Here are a few things to keep in mind when seeking to attract wildlife to the garden.

1) Plant trees, if you have room, plant a native oak. There is nothing better you can do than to plant a native oak--as they support far more species of wildlife than any other plant! 

2) Plant mostly natives. I get it, is it fun to plant some non-natives. Studies show that if a garden has at least 70% natives it will help wildlife reproduction.

3) Use plants to feed hummingbirds instead of feeders. Native Salvias, Sphaeralcea, Ribes, and so many more feed hummingbirds, bees, and other insects. Keep in mind a hummingbird’s diet ideally is 80% INSECTS not nectar from a feeder. Planting plants gives a home to the insects a hummingbird and her babies depend on for good health.

4) Leave some mess in your garden. Last year’s hollow stems, will be home to this year’s baby bees. That pile of rocks or wood in the corner can house bees, lizards and more. Leave bare earth for native bees to nest in.

5) When planting, keep in mind vertical space. Species richness is always higher in gardens with trees, shrubs, and groundcovers. Gardens with only perennials are poor in richness.

6) Include a water feature accessible by wildlife

7) Keep an organic garden free from all pesticides.

A Mix of Native and Non-native Plants                                                                      S. Reeve

The biological richness of San Diego County means we have a large number of species of plants to choose from. And the great thing is these plants are gorgeous and occur nowhere else in the world! So let’s do this! Let’s plant natives, let’s bring back the waning populations of birds, butterflies, and bees. We have the power to keep San Diego biologically rich and diverse.