Background and Aims:

The subtribe Gonolobinae is one of the most diverse subtribes of the family Apocynaceae, and its taxonomic history continues to undergo numerous changes. Within the subtribe, Matelea, the genus in which more than 200 species have been recognized has changed its circumscription the most, as it has been recovered as paraphyletic in phylogenies. This work proposes the recognition of a new genus that includes Matelea congesta. The relationship with phylogenetically related taxa is also discussed. In addition, a taxonomic treatment of the new genus is presented, in which a new species is proposed.

Methods:

Both live and herbarium specimens were observed, including types. Taxonomic literature related to the taxa treated was consulted, and a revision of the genus was carried out. A distribution map was prepared. The conservation status was evaluated according to IUCN Red List standards.

Key results:

The genus Mexicania is proposed with two species endemic to Mexico, one of them named as new, M. guerrerensis (Guerrero). The shape of the bracts, the length and pubescence of the corolla, as well as its distribution, are the attributes that allow separation of both species. An identification key, images and descriptions of its species are provided, as well as a comparison with phylogenetically related taxa.

Conclusions:

Mexicania is a sister genus to Polystemma, and is distinguished by numerous vegetative and reproductive attributes. This taxon increases to five the number of endemic genera of Apocynaceae for Mexico.

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