Molecular evidence on the species status and phylogenetic relationships of Spiranthes parksii, an endangered orchid from Texas

摘要

New genetic information on the taxonomic status of an endangered species may have strong implications for its continued protection and that of other listed taxa with questionable species status. While analyzing a more comprehensive project on the molecular phylogeny of North American Spiranthes (Orchidaceae), lack of genetic differentiation between endangered S. parksii, endemic only to Texas, and a common local congener, S. cernua, was discovered. To confirm these results in a comparative context, we focused parsimony analyses on a subset of data from local Spiranthes and the same congeners found elsewhere, expanded by additional local samples of the two focal species. Four DNA sequence segments (two chloroplast, one mitochondrial, one nuclear ribosomal) totaling 3191 base pairs were used separately and together to verify that S. parksii is nested within the same clade as S. cernua, and thus likely to be the same species. Our results concur with another recent investigation using AFLP and microsatellite data that also suggests S. parksii is not unique genetically. Therefore, based on empirical data and the phylogenetic species concept, endangered S. parksii is merely an aberrant local phenotype of and a synonym for S. cernua sensu lato. Our results should be considered during the current review of this orchid’s listing status, despite some recent policy changes on consideration of genetic data after listing.