• Native Bee Society of BC

What Pollinates a Poisonous Plant?

By Riley Wates, NBSBC Board Member

April 27, 2020

On left, death camas beginning to flower (Sooke, BC). On right, flowering

camas (Saanich, BC). Photos taken by Riley Waytes.


Meadow death camas (Toxicoscordion venenosum, syn. Zigadenus venenosus) is a flowering plant native to British Columbia. On the coast the creamy-white flower clusters of death camas can often be found in the vicinity of the blue-flowered common camas (Camassia quamash) (Pojar and Mackinnon 1994). Despite their similar names, death camas is not closely related to common camas. However, the bulbs of both plants can be easily mistaken for each other, which can be problematic where the species co-occur. While camas bulbs are edible, death camas bulbs are not. Their consumption can have very dire consequences for humans and other animals and may prove fatal. Meadow death camas contains neurotoxic alkaloids, including zygacine. All parts of the plant are considered toxic, including the roots, leaves, and flowers.

Field of death camas flowers. Photo taken at Whistler, BC by Jasna Guy.


Death camas is rarely visited by most pollinators, for good reason. The poisonous compounds produced by death camas plants (Toxicoscordion spp.) have been found in both the nectar and pollen (Cane et al. 2004). Adult pollinators feeding on nectar or pollen would therefore ingest the plant poison as well, as would any larvae fed death camas pollen. Research suggests that the consumption of death camas toxins by generalist pollinators such as honey bees (Hitchcock 1959) and blue orchard bees (Cane et al. 2004) results in significant bee mortality.


And yet there is one native bee that has a very special relationship with death camas. The mining bee Andrena astragali is one of the few pollinators that visits death camas species. In fact, its name seems to be a misnomer. While the species title ‘astragali’ suggests this bee has strong relationship with Astragalus species, A. astragali specializes on death camas species (Cane 2018), largely eschewing other plant species. It’s an amazing mutualism between a poisonous plant and a native bee. Not surprisingly, the common name of this bee is the ‘death camas andrena.’

Andrena astragali on death camas. Photo taken at Whistler, BC by Jasna Guy.


Another pollinator native to British Columbia, Eristalis hirta (syn. hirtus), has been known to visit death camas species as well (Tepedino 1981). Unlike A. astragali, this fly does not specialize solely on death camas.

Eristalis on death camas. Photo taken near Princeton, BC by Lori Weidenhammer.


The next time you encounter death camas, take a moment to look for A. astragali to appreciate this extraordinary relationship.

Andrena astragali on death camas. Photo taken at Whistler, BC by Jasna Guy.

References:

Cane, J., Weber, M., Yost, M., and Gardner, D. 2004. Alkaloids and old lace: pollen toxins exclude generalist pollinators from death camas (Toxicoscordion [=Zigadenus] paniculatum) (Melanthiaceae). In Botany Conference, Salt Lake City, UT, USA. http://2004.botanyconference.org/engine/search/index.php?func=detail&aid=1128.


Cane, J. 2018. Co-dependency between a specialist Andrena bee and its death camas host, Toxicoscordion paniculatum. All PIRU Publications. Paper 798. https://digitalcommons.usu.edu/piru_pubs/798

Hitchcock, J. D. Poisoning of honey bees by death camas blossoms. Am. Bee J. 1959, 99, 418−419.


Pojar, J. and Mackinnon, A. 1994. Plants of Coastal British Columbia. Lone Pine Publishing. Vancouver, BC, Canada. 527 pp.


Tepedino, V.J. 1981. Notes on the reproductive biology of Zigadenus paniculatus, a toxic rangeplant. The Great Basin Naturalist 41: 427-430.

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