ibclogo XVI International Botanical Congess


Abstract Number: 5761
Poster No. = 417


SOME ANATOMICAL FEATURES ON THE CYPSELA OF THE GENUS ACOURTIA (MUTISIEAE, NASSAUVIINAE) AND THEIR TAXONOMIC IMPLICATIONS.


Leticia Cabrera R., Department of Biological Sciences, Western Illinois University, Macomb, IL 61455, USA.


Historically, the generic boundaries of Acourtia have been controversial and in the past the genus has been included within Perezia although, currently, most workers recognize Acourtia as a distinct genus. Within the last two decades, its intrageneric boundaries have also been questioned and some workers have doubted the monophyletic status of the genus. As part of a search for informative characters to determine the boundaries of Acourtia, the cypsela anatomy of 55 Acourtia species was studied. Cypsela and seed development were studied for two selected species based on availability: A. mexicana, a caulescent species, and A. runcinata, a scapiform species. My results indicate that the caulescent group, with rare exceptions, possesses six to ten vascular bundles within the pericarp, and that the seed possesses a parenchymatic testa epidermis, while the scapiform group possesses five vascular bundles within the pericarp and a sclerified testa epidermis. The caulescent group has a tendency for a pericarpal wall to be present at maturation as an aerenchymatic tissue, while in the scapiform group the pericarpal wall is completely digested. The anatomy of the cypsela combined with other morphological data, strongly support the separation of Acourtia into at least two different evolutionary lineages, one involving all the scapiform species and another including all the caulescent species.


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