A biosystematic study of the rare plant
Paronychia virginica Sprengel (Caryophyllaceae)
employing morphometric and allozyme analyses
Wendy L. Rohrer
(ABSTRACT)
Paronychia virginica Spreng. (Caryophyllaceae) is a perennial evergreen herb of exposed,
relatively xeric habitats. Approximately 10 mid-Appalachian populations remain in
Virginia, West Virginia, and Maryland and are disjunct from populations located primarily
in Texas, Oklahoma, and Arkansas. A study was conducted to test the hypothesis that
eastern and western populations differ significantly and, therefore, represent at least two
distinct taxa. Statistical analyses of 8 qualitative and 24 quantitative morphological
characters indicated very highly significant (P < 0.001) variation between eastern and
western populations of P. virginica. Characters differing most significantly included sepal
pubescence, awn length, awn pubescence, awn curvature, length-width ratio of leaves, and
shape of leaf apices. Starch gel electrophoresis was performed and six enzyme
systems/nine loci (EST-2, EST-3, LAP, MDH-1, MDH-2, PGI, PGM-1, PGM-2, and
SKDH) were identified as being consistently scorable and informative. Although gene
flow between populations of P. virginica was shown to be restricted (mean FST = 0.353),
populations are maintaining relatively high levels of genetic diversity. Genetic variability
was quantified for each population and mean values for number of alleles per locus (A),
percent loci polymorphic (P), and expected heterozygosity (HEXP) were found to be 1.95,
47.22%, and 0.204, respectively, exceeding those values reported for seed plants,
widespread species, and endemic species. Hierarchical F statistics suggest higher levels of
genetic variability within individual populations than among populations, regardless of
geographic location. All statistically significant (P < 0.05) deviations from Hardy-Weinberg
equilibrium indicated a deficiency in heterozygotes at the respective loci.
Considering results from both the morphometric and allozyme analyses, the current
author suggests recognizing two distinct subspecies, P. virginica subsp. virginica in the
eastern U.S. and P. virginica subsp. scoparia in the south-central U.S. Conservation
efforts should be focused on the maintenance of existing populations in both eastern and
western regions of the U.S. in order to preserve the genetic and evolutionary potential of
these taxa.
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