Year of Pollination: Pollinator Walk at Earthly Delights Farm

Last week I had the privilege of attending a pollinator walk with a local entomologist at Earthly Delights Farm, a small, urban farm in Boise, Idaho. The entomologist was Dr. Karen Strickler, an adjunct instructor at College of Western Idaho and the owner of Pollinator Paradise. A small group of us spent a couple of hours wandering through the farm looking for pollinators and discussing whatever pollinator or non-pollinator related topic that arose. Earthly Delights Farm, along with growing and selling produce using a subscription-based model, is a seed producing farm (and part of a larger seed growing operation called Snake River Seed Cooperative), so there were several crops flowering on the farm that would typically be removed at other farms before reaching that stage, such as lettuce and carrots. The farm also shares property with Draggin’ Wing High Desert Nursery, a nursery specializing in water efficient plants for the Intermountain West, which has a large demonstration area full of flowering plants. Thus, pollinators were present in abundance.

A series of isolation tents over various crops to help prevent cross pollination between varieties.

A series of isolation tents placed over various crops to help prevent cross pollination between varieties – an important component of seed saving.

While many groups of pollinators were discussed, including leafcutter bees, bumblebees, honeybees, sweat bees, hummingbirds, and beetles, much of our conversation and search was focused on syrphid flies. Flies are an often underappreciated and overlooked group of pollinators. While not all of the 120,000 species of flies in the world are pollinators, many of them are. The book Attracting Native Pollinators by the Xerces Society has this to say about flies: “With their reputation as generalist foragers, no nests to provision, and sometimes sparsely haired bodies, flies don’t get much credit as significant pollinators. Despite this reputation, they are often important pollinators in natural ecosystems for specific plants, and occasionally for human food plants.” They are especially important pollinators in the Arctic and in alpine regions, because unlike bees, they do not maintain nests, which means they use less energy and require less nectar, making them more fit for colder climates.

One food crop that flies are particularly efficient at pollinating is carrots. According the Xerces Society, carrot flowers are “not a favorite of managed honeybees.” Most flies do not have long tubular, sucking mouthparts, so they search for nectar in small, shallow flowers that appear in clusters, such as plants in the mint, carrot, and brassica families. Flower-visiting flies come in search of nectar and sometimes pollen for energy and reproduction. While acquiring these meals they can at times inadvertently collect pollen on their bodies and transfer it to adjacent flowers. They are generally not as efficient at moving pollen as other pollinators are, but they can get the job done.

Blister beetle on carrot flowers (a preferred food source of flies). Beetles can be important pollinators, even despite chewing on the flowers as they proceed.

Blister beetle on carrot flowers (a preferred food source of flies). Beetles can be effective pollinators as well, even despite chewing on the flowers as they proceed.

During the pollinator walk, we were specifically observing flies in the family Syrphidae, which are commonly known as flower flies, hoverflies, or syrphid flies. Many flies in this family mimic the coloring of bees and wasps, and thus are easily confused as such. Appearing as a bee or wasp is a form of protection from predators, who typically steer clear from these insects to avoid being stung. The larvae of syrphid flies often feed on insects, a trait that can be an added benefit for farmers and gardeners, particularly when their prey includes pest insects like aphids. Other families of flies that are important pollinators include Bombyliidae (bee flies), Acroceridae (small-headed flies), Muscidae (house flies), and Tachinidae (tachinid flies).

Common banded hoverfly (Syrphus ribesii) - one species of hundreds in the syrphid fly family, a common and diverse family of flower visiting flies (photo credit: www.eol.org)

Common banded hoverfly (Syrphus ribesii) – one species of thousands in the syrphid fly family, a common and diverse family of flower-visiting flies (photo credit: www.eol.org)

Because many species of flies visit flowers and because those flies commonly mimic the appearance of bees and wasps, it can be difficult to tell these insects apart. Observing the following features will help you determine what you are looking at.

  • Wings – flies have two; bees have four (look closely though because the forewings and hindwings of bees are attached with a series of hooks called hamuli making them appear as one)
  • Hairs – flies are generally less hairy than bees
  • Eyes – the eyes of flies are usually quite large and in the front of their heads; the eyes of bees are more towards the sides of their heads
  • Antennae – flies have shorter, stubbier antennae compared to bees; the antennae of flies also have bristles at the tips
  • Bees, unlike flies, have features on their legs and abdomens designed for collecting pollen; however, some flies have mimics of these features
Bumblebee on Echinacea sp.

Bumblebee visiting Echinacea sp.

Another interesting topic that Dr. Strickler addressed was the growing popularity of insect hotels – structures big and small that are fashioned out of a variety of natural materials and intended to house a variety of insects including pollinators. There is a concern that many insect hotels, while functioning nicely as a piece of garden artwork, often offer little in the way of habitat for beneficial insects and instead house pest insects such as earwigs. Also, insect hotels that are inhabited by bees and other pollinators may actually become breeding grounds for pests and diseases that harm these insects. It is advised that these houses be cleaned or replaced regularly to avoid the build up of such issues. Learn more about the proper construction and maintenance of insect hotels in this article from Pacific Horticulture.

A row of onions setting seed at Earthly Delights Farm. Onions are another crop that is commonly pollinated by flies.

A row of onions setting seed at Earthly Delights Farm. Onions are another crop that is commonly pollinated by flies.

Carrots and Strawberries, Genetics and Phylogenetics

This is the fifth in a series of posts reviewing the 17 articles found in the October 2014 Special Issue of American Journal of Botany, Speaking of Food: Connecting Basic and Applied Science.

As expected, some of the articles in this issue get into pretty deep discussions about genetics and phylogenetics. Advancements in sequencing and analyzing DNA have not only led to better understanding of genes and their functions but have also given us greater insight into how species are related and their proper place on the phylogenetic tree.  While I have some background in these things and can follow along at a basic level, I certainly don’t feel confident in authoritatively summarizing such findings . I also question whether or not a high level discussion of phylogenetics makes for an interesting and engaging blog post. Plant systematics geeks are aggressively nodding “yes”; other readers’ eyes have glazed over by this point.

I am certainly not arguing that this is not important stuff. When a species we have become familiar with is suddenly given a new scientific name, it is not too annoy those of us who are trying to learn the names of things, rather it is because something novel has been discovered about the way living things are organized, about their life history – the way they came to be.  We should be celebrating advancements that allow us to look back over the millions of years of life on earth and see how various species emerged, evolved, disappeared, were replaced, and ultimately arrived at what we view today. And we should be humbled to know that these present forms are not the climax, that we are simply getting a glimpse in the evolutionary trajectory of the organisms around us. Perhaps it will prompt us to protect them, understanding that every scrap of biodiversity is important and worth conserving. After all, who are we to decide how the story goes?

The sixth and seventh articles in “Speaking of Food” are about carrots and strawberries respectively. Discussion about the genetics and phylogenetics of these plants dominates the articles, with the application being that we can improve these crops by better understanding their genetics, and we can gain insights into plant evolution by better understanding their phylogenetics.  Rather than give you a thorough overview of each of these articles (for reasons stated above), I am offering you bullet points of a few of the things that I learned while reading them.

Phylogenomics of the Carrot Genus (Daucus, Apiaceae) by Carlos Arbizu, Holly Ruess, Douglas Senalik, Philipp W. Simon, and David M. Spooner

  • The domesticated carrot (Daucus carota subsp. sativus) is “the most notable cultivated member of Apiaceae [a family consisting of 455 genera and over 3,500 species] in terms of economic importance and nutrition.”
  • Carrots are our primary source of vitamin A (due to high levels of alpha and beta carotenes), “accounting for about half of dietary intake.”
  • Wild carrot species can be used to improve the domesticated carrot by providing genes that will help with pest and disease resistance, yield increases, better nutrient value, etc.
  • “The taxonomy of D. carota is particularly problematical. It undergoes widespread hybridization experimentally and spontaneously with commercial varieties and other named subspecies.”
  • The researchers, upon examining more than half of the known Daucus species and 9 species that are very closely related, identified several Daucus spp. that “may be easily incorporated in carrot breeding programs.”
  • This study determined “misidentifications in germplasm collections” and highlighted “the difficulty of defining subspecies of D. carota.”
Flowers of Daucus carota (photo credit: www.eol.org)

Flowers of Daucus carota (photo credit: www.eol.org)

Fragaria: A Genus with Deep Historical Roots and Ripe for Evolutionary and Ecological Insights by Aaron Liston, Richard Cronn, and Tia-Lynn Ashman

  •  Fresh strawberries are fifth on the list of fresh fruit consumption in the United States.
  • “Resistance to a Fragaria-specific powdery mildew has been demonstrated in F. x ananassa [domesticated strawberry] transformed with a peach locus, and the cultivation of such transgenic plants could reduce pesticide usage in strawberry.” Commercial production awaits, though, “due to public resistance, a lack of industry support, and concerns over gene flow to the wild species of Fragaria.”
  • “The modern cultivated strawberry, Fragaria x ananassa, originated in the 18th century in Europe from hybridization between two species imported from North and South America. The parental species, F. virginiana and F. chiloensis, also hybridize naturally in northwestern North America, but there is no evidence that they were ever cultivated by the native Americans in this area.”
  • The stolons of strawberry plants can be used as dental floss!? So said Antoine Nicolas Duchesne in his 1766 book about strawberries. I guess I’ll have to read his account to get more insight into this interesting detail.
  • F. x ananassa has flowers that are self-compatible, but it is “derived from the hybridization of two wild species that show gender dimorphism,” which is common in the genus. For this reason, Fragaria, is “proving to be an exceptional model system for understanding the sexual system and sex chromosome evolution.”
  • Fragaria species occur across a broad range of temperate habitats and elevations from sea level sand dunes to moist, productive meadows to high, dry, mountain summits.” They are adapted to a wide variety of environmental conditions. “This variation represents a potential source of genetic variation for climatic tolerance, disease/pest resistance, and yield-associated traits.”
  • The Fragaria genus, like virtually all genera of flowering plants, includes polyploid species. Researchers conclude that Fragaria is an “ideal system for exploring relationships between ploidy formation, ploidy level, and the coordination of transcriptomic control.” They also believe that continued studies of “ecological and evolutionary genomics in Fragaria has the potential to provide further insights into hybridization.”
  • Finally, the researchers advise that the “familiarity of strawberries provides an opportunity to engage and educate the public about botanical research.”
Broadpetal Strawberry, Fragaria virginiana supsp. platypetala (photo credit: wikimedia commons)

Broadpetal Strawberry, Fragaria virginiana supsp. platypetala (photo credit: wikimedia commons)