Nearly a century later, rare climbers rediscovered in Assam

Guwahati: In a remarkable development for Indian botany, researchers have reported the re-collection of two little-known climbing plants—Cynanchum corymbosum and Oxystelma esculentum—from Assam after gaps of 67 and 87 years, respectively. The discovery underscores the critical importance of sustained field surveys and conservation in one of the world’s richest biodiversity hotspots.

The study was conducted by researchers Gitartha Saikia, Saurav Kumar Boruah, Trishna Roy Prodhani, and Nilakshee Devi from the Plant Taxonomy Laboratory, Department of Botany, Gauhati University, and the Department of Botany, Abhayapuri College, Bongaigaon. Their findings were published in the Journal of Threatened Taxa.

Asclepiads, the family to which these plants belong, are vital components of tropical ecosystems. Their complex flowers have evolved in close association with specialized pollinators, highlighting their ecological significance.

Both plants are members of the milkweed subfamily Asclepiadoideae under the family Apocynaceae, known for intricate flowers with highly specialized reproductive structures crucial for pollination ecology. Cynanchum L. and Oxystelma R.Br. are climbing genera native to the tropics and subtropics.

A Long Gap in Records

Cynanchum corymbosum, first described by Scottish botanist Robert Wight in 1834, was last collected in Assam by taxonomist G. Panigrahi in 1957 from Kakoi Reserve Forest in North Lakhimpur. Until now, no further records existed from the state. Its new sightings at Hajo in Kamrup and Kakoijana Reserve Forest in Bongaigaon mark its reappearance after nearly seven decades.

Even more striking is the rediscovery of Oxystelma esculentum, a little-known climbing herb with bell-shaped flowers, last collected from Goalpara in 1937. With no records for 87 years, the plant’s presence in Assam had almost faded from scientific memory. Its recent collection confirms that remnants of its population still survive in the state, albeit in very limited numbers.

Clues from the Wild

The researchers observed that Cynanchum corymbosum thrives along roadside forest edges and in scrub jungles, often twining on bamboo, teak, and other climbers like Mikania micrantha and Tinospora cordifolia. Field notes recorded pollination activity by butterflies such as the Common Leopard (Phalanta phalantha) and Common Swift (Pelopidas agna), as well as the Black Garden Ant (Lasius niger), highlighting the intricate ecological networks these climbers are part of.

Another noteworthy observation was the presence of paired fruits—a rare feature in Cynanchum, where single follicles are more typical. This finding could provide fresh insights into the reproductive biology of the species.

Conservation Alarm

While the rediscovery is a cause for celebration, it comes with a note of caution. Researchers found only a handful of Oxystelma esculentum plants in the wild, raising serious concerns about its survival. “The occurrence of very limited populations calls for immediate attention to conserve this species in its natural habitat,” the study notes.

Given the long gaps in records, botanists believe these plants may be highly localized and vulnerable to habitat disturbance. Assam’s rapidly changing landscape, coupled with pressures from urbanization and invasive species, adds to the risk.

The rediscovery of these climbers not only fills critical gaps in botanical knowledge but also serves as a reminder of the urgent need for targeted conservation efforts in the region’s biodiversity-rich forests.

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