Title page for ETD etd-4320112349751421

Type of Document Master's Thesis
Author Speer, William D.
Author's Email Address wispeer@vt.edu
URN etd-4320112349751421
Title Systematics of Eastern North American Bracken Fern
Degree Master of Science
Department Biology
Advisory Committee
Advisor Name Title
Porter, Duncan M.
Turner, Bruce J.
Hilu, Khidir W. Committee Chair
  • plant systematics
  • allozyme
  • pteridophyte
  • univariate analysis
  • multivariate analysis
  • clinal variation
Date of Defense 1997-05-07
Availability unrestricted

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.

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