An Eye On Plants: Pogostemon guamensis

By Jon Letman

Inherent in the notion of discovery is a sense of immediacy, but the truth is, quite often a plant unknown to science may be first collected many years before it is identified, recognized, and published as a “new species.” Take the Pogostemon guamensis, for instance.

First collected by botanist Derral Herbst on Guam in 1982, a second round of collections was made by NTBG botanists Steve Perlman and Ken Wood twelve years later while conducting a U.S. Fish and Wildlife Service-funded survey of the karstic limestone cliffs on Guam’s northeastern tip.

Known for their rappelling and cliff collecting skills, Steve and Ken were commissioned to spend part of spring and summer 1994 suspended by ropes exploring Guam’s jagged high cliff habitat. Steve recalls working in the blinding July heat, buzzed by Mariana crows and soaring fruit bats as they documented the then unidentified member of the Lamiaceae (mint family) in five separate sub-populations.

Upon their return to NTBG, senior research botanist Dr. David Lorence suspected the plant belonged to Position, a genus of nearly 80 accepted species with high diversity in the Indian subcontinent, but then unknown from Micronesia or other Pacific Islands. At the request of NTBG research associate Dr. Warren Wagner, a specimen was sent for DNA analysis to the Smithsonian Institution where Warren also commissioned scientific illustrator Alice Tangerini to do a line drawing.

The species holotype (representative specimen) collected by Steve and Ken is curated in the type cabinet at NTBG’s herbarium with its duplicates (called isotypes) shared with six other institutions including the University of Guam, the Bishop Museum in Honolulu, and the U.S. National Herbarium at the Smithsonian Institution.

Because of the low number of individuals (113 recorded) and its very restricted range, the species was given a preliminary IUCN assessment of Critically Endangered. The plant grows only on cliffs surrounding Andersen Air Force Base and is isolated from people, but it is thought to be threatened by invasive species, typhoons, and possibly animals such as feral pigs and deer.

Using molecular and morphological data, David Lorence, Warren Wagner, and collaborators determined the plant was in the genus Pogostemon (meaning ‘bearded stamen’) and appropriately named the species for its home island. Interestingly, unlike its relative Pogostemon cablin (patchouli) which is well-known for its pungent, musky smell, P. guamensis is scentless, like other Lamaiaceae found in Hawaiʻi.

Finally, in December 2020 Pogostemon guamensis was published in the peer-reviewed open access journal PhytoKeys. Some might ask, why did it take so long?

In the words of Dave Lorence, “The wheels of taxonomy grind slowly but very finely.” Ironically, Steve points out that not all undescribed species are published so fast. This species, like many others, was a side project, and among the 500-1,000 species across the Pacific that NTBG scientists are studying at any given time. With stretched resources and a limited number of classically trained taxonomists and experts available, publication can take years.

Pogostemon guamenis is another example of the importance of conducting field work in remote and under-studied areas, says Dave. “There are still plants out there that we hadn’t known existed until the survey work was done. It’s really important to study and name the plants before they go extinct.”

Presently, there are no known P. guamensis in cultivation and so conserving the species would require returning to its known locations to collect seeds and/or cuttings. Ken says, “Having the publication will make more people aware that this species exists and hopefully they will start conserving it.”

Illustration by Alice Tangerini
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