Rediscovering a “Lost” Plant in San Diego

It hadn't been seen in over 130 years.

We thought it was extinct, but one of the lost plants we were searching for in Baja California was rediscovered right in our own backyard.

This native grass, Sphenopholis interrupta subsp. californica, was only known through two voucher specimens collected in the state of Baja California, Mexico, in April 1886. Botanist Charles Orcutt collected both vouchers on the same trip to Baja California, one from "Northern Baja California, near the U.S. boundary" and one at "San Ramón" between Colonet and San Quintín. Herbarium vouchers are a pressed, dried plant sample mounted on paper and deposited for future reference. With only two samples, it seemed to be a singular find, not seen since and thought to be extinct. As such, it was one of the 15 "Lost Plants of Baja California" our Botany Department set out to find (learn more about that here).

Though a humble grass, it hasn't been seen in 134 years and demonstrates the resilience of native species here at home.

On April 23 2020, Margie Mulligan, Botany Department associate at The Nat, and Jessie Vinje, a botanist with Conservation Biology Institute, discovered it on two small clay lenses in central Carlsbad. A clay lens is a deposit of fine-grained soils that are thick in the middle and thin toward the edges, resembling a convex glass lens. They were studying another rare species, the federally-listed San Diego thorn-mint (Acanthomintha ilicifolia), and came across an unusual grass growing on the same lens that could not be identified with available grass keys. Keys are tools used to identify plants by a sequence of choices about the plant's characteristics. They enlisted the help of Dr. Jon Rebman, Curator of Botany, and he was able to connect it to one of the lost species on his search list.

The incredible thing about this find right here in San Diego is that it not only represents a rediscovery of a presumed extinct grass last collected by Orcutt in the late 1800s but also a new record for the United States. Recent botanical surveys by the Botany Department at the San Ramon location in Baja California were unsuccessful in relocating this grass because very little natural habitat remains for this species. These areas are heavily impacted by agriculture and urban development resulting in extreme habitat loss and fragmentation. Very little native habitat remains in the vicinity of the second Orcutt collection, "near the U.S. boundary," which is likely within present-day Tijuana.

Invasive and non-native grasses have largely decimated our native annual grasses. The botanists are proposing surveys of the remaining clay lens habitats near the coast in western San Diego County and northwestern Baja California, which could determine if additional populations of this taxon exist.

Also interesting is that there is potential evidence showing this grass is actually an entirely new species in its own right, rather than a subspecies. Now, our Botany team is looking to conduct genetic work to confirm this, coordinating with other California grass experts and waiting on funding. Also, they'll continue to look for new locations in San Diego and northern Baja California.

San Diego County is one of the most botanically diverse regions in the United States with nearly 2,900 plant taxa. Despite being a well-documented county, we continue to find new native records and new plants to science. This discovery shows that even in areas that have been visited by experienced botanists, an extinct grass (and a new U.S. record), can be hidden, waiting for the perfect environmental conditions to reveal itself.

Ultimately, the rediscovery of this grass is a story of resilience—our native species might still be out there and might still be saved if we know where and how to look for them.

Featured are Jessie Vinje from the Conservation Biology Institute, and Margie Mulligan from The Nat. Both women scientists recently rediscovered Sphenopholis interrupta subsp. californica.

Sphenopholis interrupta subsp. californica held in hand after its recent rediscovery.

A length of Sphenopholis interrupta subsp. californica after its recent rediscovery in the field.

A sample of Sphenopholis interrupta subsp. californica will be further examined and added to the Herbarium at The Nat.

A sample of Sphenopholis interrupta subsp. californica will be further examined and added to the Herbarium at The Nat.

Posted by Stephania Villar, Digital Communications Manager on July 16, 2020

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