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- Title
Examination of the highly variable P8 region (trnL-UAA intron) in the genus Equisetum.
- Authors
Speer, William D.
- Abstract
Sequences covering the highly variable P8 region of the chloroplast trnL-UAA intron from 68 Equisetum specimens representing 17 species and 1 hybrid taxon were examined in this study. P8 sequence lengths ranged from 47 to 82 base pairs. The length variation was mostly due to several, mostly contiguous, indels that were observed among the Equisetum species. One indel reliably separated subgenus Equisetum from subgenera Paramochaete and Hippochaete. P8 structures were consistent among conspecific sequences except for E. palustre. The species E. laevigatum and E. myriochaetum had almost identical P8 secondary structures, as did also E. hyemale/E. praealtum, E. giganteum/E. xylochaetum, E. ramosissimum, and E. variegatum. Sequences had a high average A-T content, ranging from 74.5% to 84.1%. Nucleotide positions toward the middle of the P8 appeared to exhibit higher variability and were more difficult to align while positions closer to the 5' and 3' ends were more conservative and easier to align. The predicted secondary structures for the P8 region tended to be very variable between subgenera and, except for the monotypic subg. Paramochaete, often within. Phylogenetic analyses of the P8 sequences used the maximum likelihood optimality criterion. Specimens representing subg. Equisetum were distinguished from subg. Hippochaete and the monotypic subg. Paramochaete (E. bogotense), with E. bogotense nesting in subg. Hippochaete in one analysis but with a sister relationship to subg. Hippochaete in the other analysis. Although conspecific specimens did group together in many cases, interspecific relationships within subgenera were generally not well resolved and often polytomous. However, P8 data did tend to reliably separate subgenera Equisetum and Hippochaete, although the position of subg. Paramochaete is somewhat questionable.
- Subjects
EQUISETUM; CHLOROPLASTS; MAXIMUM likelihood statistics; CHLOROPLAST DNA; INTRONS
- Publication
Journal of the Utah Academy of Sciences, Arts & Letters, 2023, Vol 100, p117
- Publication type
Article