Trout lilies (Erythronium americanum)

Every year, I look forward to the spring ephemerals. Not only are many of them beautiful, but their resilience after the long winter is admirable. Trout lilies are one of my favourites. These fascinating plants have mutualistic relationships with ants, help in nutrient cycling, and can produce different pollen colours.

Description

Trout lilies are native to eastern Canada and northeastern United States. They crop up in early spring, around April and May, after the snow melt, but before the deciduous trees leaf out.

Trout lily leaves are waxy and green with brownish-purple patches. Their common name comes from these speckled leaves which are reminiscent of the brown trout or brook trout.

You’ll find these plants growing in large colonies, forming a dense carpet on the forest floor. Young plants have one leaf and older plants have two. On average, it takes seven years for a trout lily to produce a flower!¹ The flowers are yellow and droop downwards. They are also “perfect flowers,” meaning they have both male and female structures (stamens and carpels).

For a full description of these plants check out the trout lily project.

Ant Allies

One of the coolest things about trout lilies are their mutually beneficial relationship with ants. These plants produce seeds with food parts called elaiosomes. Elaiosomes are fleshy, calorie and nutrient dense structures attached to seeds. Worker ants seek out these seeds to bring back to their colony. After feasting on the elaiosomes, the ants throw out the remaining seed and it is able to germinate.

It’s a win-win situation. The plants have their seeds spread and the ants get nutritious food. Plants with mutualistic relationships with ants are called myrmecochory plants.

Nutrient Cycling

Another cool thing about these plants is their role in nutrient cycling. In 1978, Muller and Bormann demonstrated that trout lilies retain “significant amounts of potassium and nitrogen.”² They hypothesized that, were it not for trout lilies these nutrients would wash away during spring flooding. While more evidence is needed to prove their hypothesis, one thing is clear, trout lilies store important nutrients and these nutrients are later released back into the environment through decomposition.

Wildlife Interactions

Trout lilies are a food source for some wildlife. Deer graze on the plant, black bear eat plant corms (underground stems), and chipmunks in the Adirondacks depend on their nutrients.³ Tessier showed that plants with shallow corms are more at risk of herbivory than those with deep corms.⁴

Pollen Color Polymorphism

Trout lilies produce both red and yellow pollen. A colony can have both colours or be all the same colour.⁵ Recently, scientists set out to understand why these differences were occurring. Using citizen science, they enlisted the help of community members to record populations across North America.

Going into the project, they had several theories about why variation was happening. Perhaps, pollen colour offered some protected against UV-B radiation or protection from the pollen-feeding beetle Asclera ruficollis. Maybe there was a noticeable geographic distribution of pollen colours. Or, could it be that pollen colour affected reproductive success? All of these hypotheses proved false.⁶

They concluded that some pollinators “exhibited site‐specific pollen‐colour preferences” and that “they may act as agents of selection on this trait” and “contribute to the maintenance of variation.”⁷

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Mayflower (Epigaea repens)

Identifying Clover (Trifolium Spp.)

Acadian Forest: History, Species, and Biodiversity

Sources

¹ Sarah Coulber. “Trout Lily.” Canadian Wildlife Federation.

² Robert Muller and Herbert Bormann. 1976. “Role of Erythronium americanum Ker. in Energy Flow and Nutrient Dynamics of a Northern Hardwood Forest Ecosystem.” American Association for the Advancement of Science.

³ “Wildflowers of the Adirondacks: Trout lily (Erythronium americanum).” Adirondacks Forever Wild.

⁴ Jack Tessier. 2020. “Shallow Corms of Erythronium americanum (Trout Lily) Die from Herbivory in the Summer and Freezing in the Winter.” Northeastern Naturalist.

⁵ Emily Austen, Shang-Yao Lin, Jessica Forrest. 2018. “On the ecological significance of pollen color: a case study in American trout lily (Erythronium americanum).” Ecological Studies of America.

⁶ Ibid.

⁷ Ibid.