Relationships Between Two Infraspecific Taxa of Pteridium aquilinum (Dennstaedtiaceae). II. Isozyme Evidence

The cosmopolitan species Pteridium aquilinum is widespread throughout eastern North America, where it is represented largely by two varieties, var. latiusculum and var. pseudocaudatum. The taxonomy of Pteridium is contentious and the taxonomic status of these two varieties is uncertain. Isozyme data...

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Bibliographic Details
Published in:Systematic botany 1998-07, Vol.23 (3), p.313-325
Main Authors: Speer, William D., Werth, Charles R., Hilu, Khidir W.
Format: Article
Language:English
Subjects:
Alleles
Biological taxonomies
Coastal plains
Evolutionary genetics
Ferns
Genetic loci
Genetic variation
Plants
Population genetics
Taxa
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Summary:The cosmopolitan species Pteridium aquilinum is widespread throughout eastern North America, where it is represented largely by two varieties, var. latiusculum and var. pseudocaudatum. The taxonomy of Pteridium is contentious and the taxonomic status of these two varieties is uncertain. Isozyme data were obtained (14 loci coding 8 enzymes) from eleven populations to assess the genetic relationships of these two varieties. High genetic identities (mean I = 0.98) were observed for all pairs of populations studied. Strong patterns of clinal geographic variation were observed at five enzyme loci, associated with decreasing levels of genetic variation in the more southern populations. This pattern showed some independence relative to varietal status, as UPGMA clustering did not separate these populations into clusters corresponding to vars. latiusculum and pseudocaudatum. Evidence of unrestricted gene flow between the two varieties was found at Greensboro, NC, where the two distinct morphotypes co-occurred. Thus, the isozyme evidence strongly indicates that these two taxa are conspecific, and that their treatment at varietal rank should be maintained.
ISSN:0363-6445
1548-2324
DOI:10.2307/2419508