Background and Aims:

During explorations in the Parque Nacional Montaña de Celaque, Honduras, a new species of Acanthocereus (Cactaceae) was discovered. The aim of the present study is to describe and illustrate A. lempirensis, and to compare it with its putatively closest relative, A. chiapensis.

Methods:

Botanical field collections were conducted during 2023. In order to compare the possible new species with other species in the genus, the collections in different herbaria and a Database of Cactaceae from North and Central America were examined and a distribution map was prepared. A preliminary assessment of the conservation status of the new species was preliminarily assessed using the IUCN Red List criteria.

Key results:

Acanthocereus lempirensis appears to be closely related to A. chiapensis by the presence in both species of green glaucous stems ramified from the base, similar spination, and nocturnal flowers. It can easily be distinguished from that species by the combination of the following morphological characters: pink perianth segments, internal perianth segments oblanceolate, rounded to retuse and mostly subacute apically, and the apical margins minutely lacerate. The species is restricted to a small area of limestone cliffs and steep slopes with tropical deciduous forests intermixed with Pinus and Quercus. Only ca. 150 individuals have been detected in the wild. A Critically Endangered (CR) conservation category is suggested for this species.

Conclusion:

This new discovery places Honduras as an important diversity center for species of Acanthocereus (five spp.), preceded by Mexico (12 spp.). The recent botanical findings in Honduras (A. canoensis y A. lempirensis) confirm the importance of continuing and supporting floristic studies in the country and the conservation it its ecosystems.

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