Background:

Polystemma has about 27 species distributed from southeastern United States to central Costa Rica. Plant collecting activities detected one taxon that does not fit the description of previously known species of the genus.

Questions:

Do the collected specimens belong to a new species? What is its conservation status?

Studied species:

Polystemma margaritadelacerdae.

Study site and dates:

Aguascalientes, 2022-2024.

Methods:

Recently collected plant material was studied to prepare a morphological description. The conservation status of the new taxon was evaluated, following the IUCN Red List criteria.

Results:

Polystemma margaritadelacerdae is proposed as a new species because of the presence of a green corolla, an exserted cylindrical gynostegial corona, with a fimbriate to denticulate lobe apex. At the moment, the new taxon is categorized as Vulnerable (VU).

Conclusions:

A new species of Polystemma is described and the number of Apocynaceae species that occur in Aguascalientes increases to 25.

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