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Marasmius plicatulus (by Christian Schwarz)

Photos and text © Christian Schwarz

We’ve probably all run across Marasmius plicatulus during our walks in the woods; the tall, brightly-colored fruitbodies occur in many kinds of habitats every year, often in large troops. And what an excellent little mushroom to be so familiar. This species has a lot of features setting it apart from the rest of it’s marasmioid brethren: electric-sunset stipe coloration, oddly wiry-stipes (often tipped in pom-poms of creamy-white mycelium), and finely velvety caps often covered in beaded-up water droplets.

But how many of us have given much thought to the geographic range and morphological variation of this species? A quick search on mushroomobserver.org (hereafter referred to as ‘MO’) gives us the following map of observations for this species:

Some interesting points to take note of:

1. As we try and familiarize ourselves with any species, it’s always a good idea to try and describe the its range in one or two simple sentences. For this one, I’d summarize it as: Pacific states, primarily coastal, common. More detailed looks at the notes and photos of these individual observations would show that it inhabits almost any kind of habitat: pine, cypress, oak, fir, spruce, really any place with trees and sufficient duff on the ground.

2. The glaring gap in southern Oregon – this is almost certainly due to the lack of observers in the area, not an actual disjunction in the distribution of the species. Just goes to show how important citizen scientists are in our effort to document the distribution of macrofungi. Going on a beer tasting tour to Oregon’s Arch Rock Brewing Company?

Take a photo of our Mushroom of the Month while you are in Curry County and help us fill in the Gap on the Map!

3. The apparent southern limit around Los Angeles – does this species really not occur in San Diego County? A quick message to Bonni McKintosh of the San Diego Mycological Society confirmed my memory that it’s common there (especially under shrubs like Toyon and Laurel Sumac)! So why the gap? Once again, lack of participation on mushroomobserver.org. Public databases like this are absolutely dependent on their users for data!

4. A closer look at the map would show a few observations away from the coast and a bit closer to the central valley, but none from the Sierra foothills or higher elevations.

Now that we’ve got a basic sense of the distribution of this species, let’s look at the morphological variation, specifically with regard to color. The montage below shows two typical forms (from the mainland and Santa Cruz Island, of the Channel Islands), and two less-common forms.

Four color forms of Marasmius plicatilis. Top left: The typical coastal form, with a red cap, and fairly dark stem showing a gradient of stipe color from black near the base to orange, pink, or white near the apex. Top right: A fairly typical form found on Santa Cruz Island, with very bright magenta and pink colors on the stipe, and nearly cherry-red caps. Bottom right: an orange-brown form (almost entirely lacking pink and red colors) from Santa Cruz Island, where it was nearly as common as the more typical form. Bottom left: the most unusually-colored fruitbodies of this species I’ve ever encountered; completely pastel-pink, with hardly a trace of orange, and none of the characteristic black or brown stipe pigmentation.

The orange-brown color form in the bottom-right photo is far from restricted to Santa Cruz Island; in fact, fruitbodies showing these colors are more commonly found in the northern reaches of this species’ range on the mainland, where the typical red form is also present. Most of the “Orange-brown Form” currently on M.O. are from Oregon: Sava Krstic’s , Daniel Wheeler’s 14662, Britney Ramsey’s 80819, 61364, and 59467; although there are a few from northern California: Darvin DeShazer’s 122671 and Douglas Smith’s 17325; Noah Siegel has also found it in Jedediah Smith Redwoods State Park in Del Norte County.

* Note: to search for any of the observations listed above, go to mushroomobserver.org and type or paste the observation number into the search bar at the top of the page as shown below.*

So what accounts for the color variation in this species? Climatic conditions don’t seem to explain the pattern, since three of the forms have been found growing right next to each other. Partially (or completely?) reproductively-isolated populations combined with random drift in pigment genes? Possibly, but it’ll take a lot of work to prove that hypothesis. Simple standing variation between freely-interbreeding populations? Possibly, but why are the bulk of orange-brown forms found north of Mendocino County? And even then, they co-occur with the “Red Form”; do any of fruitbodies in these areas show intermediate coloration? All these questions remain to be answered.

As I hope I’ve shown with this month’s article, we have much to learn about even the most common and familiar mushrooms. No area is too small, no question too basic! Get out there and document what you see. Take notes, take pictures, take specimens for an herbarium. With the help of citizen scientists like you, we’ll make more rapid progress to a Mycoflora of North America.

- Christian Schwarz