New Orange-Fruited Casearia napoensis Is Critically Endangered

In the limestone mountains of western Guangxi, a tree bearing bright orange-red fruit has been growing unnoticed inside a nature reserve. After survey work that ran from May 2024 to May 2026, botanists have formally described it as a species new to science: Casearia napoensis, named for Napo County where the team found it. The news comes with a warning. The researchers located only seventeen individuals of Casearia napoensis, and only two of them are mature, a population so small that the study assesses the tree as Critically Endangered under international red-list criteria.

A tree hiding in plain sight

The tree belongs to Casearia, a pantropical woody genus most diverse in the Neotropics. What makes Casearia napoensis stand out is its fruit. The capsule is spherical, leathery, about three centimeters across, and ripens to a vivid orange-red before splitting into four or five valves, each fleshy, with a single fruit able to carry up to sixteen seeds. The valve count is the giveaway. The new species' closest relatives in China split their capsules into fewer valves, which helped the researchers separate Casearia napoensis from every species already on the books.

The tree itself is small, with a straight trunk, grayish-white bark, thinly leathery leaves, and clusters of tiny green flowers that open from April to June. Fruit follows from August to November. The research team, led by T. Xu, L. Gong, Z. L. Ouyang and Z. Y. Su, carried out thirteen field surveys at the type locality and compared fresh material against herbarium specimens held in collections across China and abroad, consulting digital type images through the JSTOR Global Plants database and the Chinese Virtual Herbarium. Voucher specimens now sit in the herbaria of Nanning Botanical Garden, Chenshan Botanical Garden and the Guangxi Institute of Chinese Medicine and Pharmaceutical Sciences, according to the study, published in the journal PhytoKeys.

Critically endangered at first sight

All of the known Casearia napoensis trees grow inside the Guangxi Laohutiao Nature Reserve, in limestone mountainous forest at about twelve hundred meters. The surveys between 2024 and 2026 turned up no other locality, which suggests the species' range is extremely narrow. With so few mature individuals, the authors applied the International Union for Conservation of Nature red-list guidelines and placed the tree in the Critically Endangered category, the classification reserved for species with very few mature individuals. Casearia napoensis is now among the most imperiled plant discoveries in the region, and a reminder that a species can be new to science and already on the brink.

There is a hopeful note. Nanning Botanical Garden collected seeds from the wild population and has raised seedlings, building an ex-situ conservation collection that could preserve the species' genetic material if the wild population declines. Whether more Casearia napoensis trees survive in unsurveyed pockets of the reserve is unknown, and the researchers say continued fieldwork will be needed to refine the population estimate. The timing is uncomfortable: the assessment arrives as the world is off track on its nature goals, according to a recent United Nations biodiversity report.

Why new trees keep turning up

Casearia napoensis is the first Casearia described from China since the Flora of China was published in 2007, which had treated the genus' Chinese members as settled. Taxonomists have not stopped finding new Casearia elsewhere. Recent years have brought fresh descriptions from Southeast Africa, Central America, South America and West Africa, and the authors of the new paper supply a revised key to the seven Casearia species now recorded from China.

The limestone karst forests of southern China are known for high endemism and heavy conservation pressure, the combination that produces species found nowhere else and at risk from the start. The discovery follows other recent finds. Earlier this month, a new giant water lily discovered in Colombia was described after a Kew horticulturist spotted photographs of it on Instagram. Both finds carry the same message: there are still plants growing out there that science has not named, and some of them are already in danger by the time they get a name.

The paper also clears up a small historical puzzle. In the original 1970 description of a related species, Casearia tardieuae, the fruit was recorded at only a few millimeters across. The new paper suggests that was a typographical error and the measurement should read in centimeters. It is a modest correction, but it shows a genus in motion: old descriptions get rechecked, keys get rewritten, and a tree that sat unnamed in a reserve finally gets its entry in the scientific record. ScienMag summarized the discovery for general readers this week.