Know your desert pollinators, and the plants they rely on
Diadasia bee covered in pollen of desert chicory (Rafinesquia neomexicana) ©Madena Asbell
By Madena Asbell, Director of Plant Conservation Programs
Pollinators are among the many animals facing challenges from climate change, invasive species, and other threats. Pollinators are an especially important part of earth’s ecosystems because they are responsible for ensuring the reproduction of most of our planet’s flowering plants.
According to the Food and Agriculture Organization of the United Nations, 3 out of 4 of the world’s food crops depend on pollinators — and not just honeybees, but wild pollinators too.
One of the most fascinating things about pollinators is their incredible diversity. Plants are pollinated by a host of different animals, including bees, butterflies, moths, flies, beetles, hummingbirds, and bats. MDLT’s new Desert Discovery Garden features planting beds designed specifically for native pollinators. Each of these gardens contains plants that attract native bees, butterflies and moths, and hummingbirds.
Let me introduce you to some of the Mojave Desert’s pollinators and the native plants they depend on.
Native bees
Bees are an incredibly diverse group of insects — the California deserts are home to an estimated 750 native bee species!
Mining bee (Adrenidae) collecting pollen from bladderpod (Peritoma arborea) ©Madena Asbell
Bees come in many shapes, sizes, and colors, from metallic green sweat bees to fuzzy orange carpenter bees to small striped mining bees.
Sweat bee (Halictidae) on desert marigold (Baileya multiradiata) ©Madena Asbell
Unlike honeybees, most native bees are solitary, building individual nests in the ground or in wood cavities. 70% of native bees in North America nest in the soil by digging underground tubes in which the female lays her eggs. Carpenter bees and mason bees build nests in wood and rock crevices.
Nests of miner bees in Joshua Tree, CA ©Madena Asbell
Bee flies and mimicry
A bee fly getting nectar from Mojave aster flower ©Madena Asbell
Some insects have evolved to resemble other species as a strategy to avoid predation. This occurs when an insect with weak defense mechanisms, such as a fly that is unable to bite or sting, mimics an insect with a strong defense mechanism, like a bee. Bee flies are not bees but flies that imitate bumblebees with their fuzzy bodies. Some bee flies even produce a buzzing sound. They have a long, straw-like mouthpart, called a proboscis, that allows them to drink nectar from flowers much as bees do, and when they visit flowers they collect and distribute pollen that sticks to the hairs on their bodies. One reliable way to distinguish between bees and bee flies is to look at their wings — bees have two pairs of wings while flies only have one pair.
Butterflies and moths
Butterflies are some of our most charismatic pollinators. Take the monarch, for instance, with its colorful orange and black markings and epic annual migrations. Most adult butterflies and moths prefer open flowers with a flat surface on which they can land and feed. This includes the daisy-like flowers of Acton encelia and brittlebush, clusters of small flowers like those of east Mojave buckwheat, and many other nectar-rich blossoms. This works out well if you have a straw for a mouth (also known as a proboscis), but what about a butterfly’s leaf-chewing larvae?
Monarch caterpillar munching on a milkweed leaf ©Madena Asbell
To complete her lifecycle a butterfly must lay her eggs on an entirely different type of plant, one that her caterpillars will eat. The plants on which caterpillars feed are called “host plants,” but unlike humans who can choose what they eat based on personal taste or what happens to be available, caterpillars have evolved to eat very specific plants — if their host plants aren’t available, butterflies and moths cannot reproduce.
Adult female monarch butterfly ©Madena Asbell
Moths are closely related to butterflies and are important pollinators too. The yucca moth is an example of a pollinator with an exceptionally close relationship with its host plant. The females of these tiny moths are not only responsible for pollinating our iconic Joshua trees, but they are completely dependent upon this pollination for their own reproduction.
Female yucca moth depositing pollen onto a yucca flower. Photo: Sherwin Carlquist
You see, yucca flowers produce pollen that is too sticky for most insects to collect, but female yucca moths have evolved specialized mouth parts that allow them to gather the pollen and place it on the pistil of the flowers.
When she pollinates a flower, the yucca moth also lays her eggs in the ovary of the blossom where the seeds will develop. The process of pollination leads to fertilization of the ovules which results in the development of seeds on which her caterpillars feed. These two organisms are dependent upon each other for reproduction in a relationship known as obligate mutualism.
Hummingbirds
Female Costa’s hummingbird visiting bladderpod flowers ©Madena Asbell
The Mojave and Colorado Deserts are home to four species of hummingbird, although not all are full-time residents. According to Kurt Leuschner, Professor of Natural Resources at College of the Desert, Costa’s and Anna’s hummingbirds can be seen in both deserts year-round, while rufous hummingbirds migrate through during spring and fall, and black-chinned hummingbirds spend only summers in the desert.
The tubular red flowers of penstemons are a hummingbird favorite ©Madena Asbell
Hummingbirds are attracted to colorful nectar-rich flowers that are funnel-shaped or tubular. Some of their favorite native plants are bladderpod, penstemons, and sages. However, nectar isn’t the only source of food for these high-energy birds — they also need protein, which they get in the form of insects. Protein is an especially important part of their diet during breeding season when they feed small insects to their developing chicks. Common insects that hummingbirds eat include aphids, spiders, and gnats.
How can you support pollinators at home?
· Plant a variety of flowering native plants that attract bees, flies, beetles, butterflies, and hummingbirds.
· Plant both nectar plants for adult butterflies and moths and the host plants that their caterpillars feed on.
· Maintain patches of open, undisturbed soil where native bees can nest.
· Construct and install a bee house for carpenter and mason bees.
· Avoid using insecticides.
· Leave spider webs alone. Hummingbirds feed on spiders and insects trapped in webs, and they use the web material to construct their nests.
· Participate in an annual butterfly count near you.
Special thanks to Hartmut Wisch for assistance with native bee identification.