Scholarly Communications Project


<ETD> Submission Form - Cataloger

Name:
William D. Speer

Email address:
wispeer@vt.edu

Title:
Systematics of Eastern North American Bracken Fern

Date of defense:
May 7, 1997

Document Type:
Master's Thesis

Degree:
Master of Science

Department:
Biology


Abstract


The cosmopolitan Pteridium aquilinum (L.) Kuhn is widespread throughout eastern North American, where it is represented primarily by Tryon's (1941) var. latiusculum (Desv.) Underw. and var. pseudocaudatum (Clute) Heller. The taxonomy of Pteridium is controversial. Fourteen isozyme loci and 12 morphological characters were used to assess the taxonomic relationship of these two varieties. Isozyme data indicated a high mean genetic identity (I = 0.976) between eleven bracken populations. Strong patterns of geographic variation for isozyme allele frequencies were also observed. The isozyme results did not separate the two taxa. Numerical analysis of the morphology distinguished the two taxa when the qualitative characters were used alone or in conjunction with some of the quantitative traits. All qualitative characters differed significantly between the two taxa. No perceptible geographic pattern of variation was observed. Morphological distinctiveness was maintained even in those localities where both taxa were present, with few or no intermediates being found. Isozyme evidence suggestive of gene flow between the two varieties was found at Greensboro, NC, where the two morphotypes were easily recognizable. The isozyme evidence strongly indicates conspecificity, while the morphological evidence supports their status at the varietal level.

Keywords:
Plant systematics, allozyme, Pteridophyte, univariate analysis, multivariate analysis, clinal variation

Availability:
In a year

Public URL:
http://scholar.lib.vt.edu/theses/public/etd-4320112349751421/etd-title.html


List of attached files

File NameSize (Bytes)
etd.pdf310,992 Bytes


Date item approved:
05/28/97

Fees:
Archiving fee received.



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