Two new taxa of Clethra (Clethraceae: sect. Cuellaria, ser. Tomentosae) from Honduras

Abstract

Background: As part of the taxonomic revision of the genus Clethra in Central America, two new species from Honduras were discovered. The two new species described here have been confused mainly with C. lanata, C. mexicana and C. salvadorensis. Question: Are foliar trichomes useful to distinguish species? Taxon: Species of Clethra. Study site: Central and southern mountain ranges of Honduras. Methods: Relevant literature on Clethra was reviewed and specimens from six herbaria were examined. Type material from all morphologically similar species, as well as those taxa with which the two new species have previously been confused were compared. Results: Clethra albertinae and C. standleyana are described and illustrated as new and endemic species from Honduras, both belong to ser. Tomentosae. Clethra albertinae is most closely related to C. licanioides, a species endemic to Guatemala, and C. standleyana is most closely related to C. nicaraguensis, a widespread species that occurs from Mexico (Chiapas) to Nicaragua. Based on the IUCN Red List a conservation assessment of Vulnerable and Endangered is recommended for both new species. An updated list and key to the nine species of Clethra for the flora of Honduras is proposed. Conclusions: The foliar trichomes turned out to be diagnostic and in combination with characters of the inflorescences can used to separate of all Honduran species of Clethra. In Central America, Honduras is the third country with most species rich of this genus after Guatemala and Costa Rica.