Dandelion diversity overlooked in British Columbia

As the snow melts and the sky clears, dandelions spring up on lawns across Canada—but take a closer look, there’s more diversity there than you might realize. British Columbia (BC) is home to a wide variety of species of Taraxacum, the large and geographically widespread genus that includes dandelions. Many of these species are exotic, mostly introduced from Europe. Collections of exotic species made in North America are typically identified as either T. officinale or T. erythrospermum, disregarding large differences in the plants’ morphology, ecology, and geographical distributions, and this lumps many species into just two.

The status quo causes confusion, since neither species description is a good match in many cases, and the genus is difficult to identify to species, even with a clearly defined key. This has led to most exotic specimens in North American herbaria being misidentified, except where they’ve been annotated by a European taxonomist.

Taraxacum celticum, section Celtica, Saanich Peninsula, British Columbia

A recent study published in Botany aims to change this. Author Curtis R. Björk of the Beaty Biodiversity Centre at the University of British Columbia applied the exacting standards of European Taraxacum taxonomy to develop a more comprehensive framework for identifying exotic species present in British Columbia. Examining over 550 specimens comprising more than 100 species of exotic Taraxacum with European origins, Björk described seven sections (the taxonomic grouping under genus) plus one unranked group present in BC, and he presents a key to facilitate accurate identification.

Taraxacum naevosiforme, section Naevosa, urban Vancouver.

The sections are Borea, Boreigena, Celtica, Erythrosperma, Hamata, Naevosa, and Taraxacum; the unranked group is T. fulvicarpum. Each of the sections contains only exotic species, and all Taraxacum sections present in BC contain only exotic or native species. Therefore, once a specimen has been identified to its section, the collector will know if they’re looking at a native or exotic plant, even if the exact species is not known.

Björk explained that his work has applications in the conservation of some of the rarer native Taraxacum species. “Many of the native species are beautiful and garden worthy. The rarest of them merit conservation efforts to ensure they don’t go extinct,” he said. “Knowledge of the native species helps to fill in gaps in our understanding of the evolution of the genus Taraxacum as a whole. None of this is possible if the native species cannot be differentiated from the exotic species.”

Taraxacum lacistophyllum, section Erythrosperma, urban Vancouver.

Björk’s work may also be valuable in studying the complex reproductive biology of this group, including understanding whether exotic and native species are hybridizing and how different reproductive strategies interact. “I see a lot of potential for research in Taraxacum evolutionary biology,” he said. “There is much that is unknown or possibly oversimplified about how dandelions reproduce and evolve. Taraxacum species can differ among each other greatly in how they reproduce.”

With a framework in place for identifying exotic Taraxacum species, Björk plans to move on to native species, which are poorly understood taxonomically. “Now that we can more accurately differentiate the native from non-native species, we can proceed to describe more native North American species new for science and start putting our native species into a greater, worldwide taxonomic context.”

Björk enjoys studying dandelions and their kin because interesting questions in evolutionary biology can be investigated using an everyday plant. “It’s exciting to me to think of how these and more questions can be addressed by studying plants that are so common and so near at hand.”

Read the paper: Overlooked diversity in exotic Taraxacum in British Columbia, Canada in Botany.