A NEW SPECIE FROM WESTERN MEXICO

Polystemma cualense (Apocynaceae)

By Dr. Cristobal Sánchez

June 17, 2026

A newly discovered plant species, Polystemma cualense, has been described from the Sierra El Cuale in Jalisco, Mexico. Found during 2024 botanical expeditions for an oak conservation project, this perennial climbing plant increases the known number of Polystemma species in Jalisco to 10, cementing the region’s status as a high-diversity hotspot for the genus.

Key Distinctions

Polystemma cualense closely resembles P. horconesense but stands out due to several distinct physical and ecological traits:

• The Gynostegium: It features a unique black gynostegium and a gynostegial corona that is noticeably higher than the gynostegium itself.

• Inflorescence & Floral Features: It has umbellate-cymose inflorescences (vs. monochasial), a single yellow colleter at the base of its sepals (vs. three), and yellow flowers (vs. brown or pale green with violet hues).

• Habitat: It thrives in temperate, subhumid conditions above 1,000 meters in altitude, whereas P. horconesense is restricted to warm, subhumid climates below 400 meters.

Conservation Status

A preliminary assessment using IUCN criteria classifies Polystemma cualense as Critically Endangered (CR). It is known from only two specific populations in the Talpa de Allende municipality, occupying a tiny area of just 8 km². Tragically, in 2025, the only three known individuals at its primary type locality were entirely destroyed by land clearing. The remaining habitats face severe, ongoing threats from deforestation, agricultural expansion, and livestock grazing.

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