Comparative Morphology of ten taxa of the genus Celtis (Cannabaceae) of South American Southern Cone

Abstract

The genus Celtis L. (Cannabaceae) comprises around 73 species distributed in temperate and tropical regions of both hemispheres. Most South American species belong to the subgenus Mertensia Planch., and they are characterized by showing high morphological plasticity. A recent taxonomic revision of this group was carried out with an excessively reductionist criterion regarding the number of accepted species and that does not clearly reflect the morphological differences among them. In order to contribute to the correct delimitation of the specific entities, a morpho-descriptive approach is presented for ten taxa of the genus Celtis (C. brasiliensis, C. chichape, C. clausseniana, C. fluminensis, C. pallida var. pallida, C pallida var. discolor, C. serratissima, C. spinosa, C. spinosissima and C. tala) growing in South American Southern Cone. The morphology was analyzed through the use of a stereomicroscope and/or the tpsDig program for digital images of specimens. As a result, a key is provided for the determination of the aforementioned species and a detailed morphological description of the vegetative (habit, bark, branches, spines, brachyblasts, indumentum and leaves) and reproductive structures (inflorescences, flowers, fruits and endocarp -pyrene-). In addition, a specimen collection guide is proposed with a list of the main morphological characters that should be observed in the field, to facilitate future identifications.