Naming the long-known: a new species of Desmopsis (Annonaceae) endemic to Mexico

Abstract Background and Aims: A frequently collected species of Desmopsis (Annonaceae) in Mexico has remained indeterminate for more than 30 years. Its floral characteristics are similar to those present in the Asian genus Guamia (now Meiogyne), and for many years it has been named “Guamia mexicana”, but not formally described. Recently, it was shown that “Guamia mexicana” is phylogenetically related to Desmopsis and Stenanona and not to Guamia. However, and despite being frequently collected, its taxonomic status has not been clarified. Here, the phylogenetic relationships and the morphological and ecological characteristics that distinguish “Guamia mexicana” from other species were studied. As a result, this new species is herein described. Methods: The new species was recognized using the unique combination of features through comparisons with morphologically similar species and a literature review. Its pollen characteristics were analysed using scanning electron microscopy. Its phylogenetic relationships were determined based on previously published phylogenies. Lastly, its conservation status was tentatively assessed by calculating extent of occurrence (EOO) and area of occupancy (AOO) using the GeoCAT tool and applying the IUCN Red List categories and criteria. Key results: A new species of Annonaceae endemic to Mexico, namely Desmopsis ibarrarum, is described and illustrated. It is distinguished from other Desmopsis species by the combination of long and cylindrical fruits with many seeds, with a hard and woody testa and densely covered by very small sericeous hairs (velvety), glabrous leaves with percurrent tertiary venation, the absence of leafy bracts on the pedicels, the morphological differentiation of internal and external petals, and the partial fusion of the sepals. Conclusions: Desmopsis ibarrarum is only closely related to Desmopsis dubia and both species are here considered members of a particular lineage within the Desmopsis-Stenanona clade, the “Desmopsis dubia group”.