Date of Award

Spring 1990

Project Type

Dissertation

Program or Major

Plant Biology

Degree Name

Doctor of Philosophy

First Advisor

Garrett E Crow

Abstract

Carex section Scirpinae is a small group of North American sedges that possess a dioecious breeding system, unispicate inflorescences and pubescent perigynia. Historically, ten different taxa had been recognized at the specific or infraspecific levels based primarily on morphological characters. Taxonomic problems in the group were related to the lack of a comprehensive monographic treatment. Floristic treatments were limited and focused only on a few regional taxa. Descriptions were often incomplete, lacking descriptions of staminate material or complicated by the inconsistent use of the terms phyllopodic and aphyllopodic. Patterns of variation in morphological characters across a wide geographic range were not understood. Little, information was available concerning chromosome numbers, anatomy, interbreeding relationships, micromorphological features and ecology.

A systematic investigation of taxa assigned to this section was carried out to: (1) circumscribe taxa, (2) examine phenetic relationships, (3) resolve the question taxonomic rank, and (4) determine whether the group was monophyletic. Based on evidence drawn from morphology, chromosome numbers, leaf anatomy and surface structure, achene and perigynium micromorphology, interbreeding relationships, ecology and distributions, six taxa are recognized in two species, one with four subspecies. The section, as treated here, consists of Carex scirpoidea Michx., with four subspecies (ssp. scirpoidea, ssp. convoluta, ssp. pseudoscirpoidea, and ssp. stenochlaena), and Carex curatorum Stacey. The subspecies of C. scirpoidea are geographically based ecotypes that differ morphologically in only a few characters. Carex curatorum is distinguished by characters of perigynium morphology, domed silica bodies of the achene, sparsely pilose leaf surfaces, a restricted distribution in riparian habitats in southern Utah and northern Arizona. The section Scirpinae forms a cohesive group of dioecious, unispicate sedges with pubescent perigynia, chromosome numbers of n = 31, similar leaf anatomy and high degree of interfertility between subspecies based on hand-pollinations.

Two taxa, Carex gigas (Holm) Mack. and C. scabriuscula Mack., previously assigned to the section, have been excluded. Plants are often not dioecious, rarely unispicate and have perigynia with few short hairs, have chromosome numbers of n = 29 and exhibit amphistomatous leaves.

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