Origin and conservation genetics of the threatened Ute ladies'-tresses, Spiranthes diluvialis (Orchidaceae)

The Ute ladies'-tresses, Spiranthes diluvialis, is listed as a threatened orchid in west-central United States by the Federal government. Information on its origin and patterns of genetic variation is needed to develop effective conservation strategies for this species. DNA sequencing and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used to evaluate genetic variation and structure of 23 populations of S. diluvialis. In addition, four congeneric species were analyzed to determine possible origins of the putative allotetraploid S. diluvialis. DNA sequencing and PCR-RFLP analysis of the nuclear ribosomal internal transcribed spacer (ITS) and mitochondrial and chloroplast DNA noncoding regions revealed no genetic variation within or among populations of S. diluvialis. DNA sequencing revealed that S. diluvialis has rDNA of both S. magnicamporum and S. romanzoffiana, supporting the proposed origin of the allotetraploid. Parsimony and maximum likelihood analyses of cpDNA and mtDNA sequences revealed that these S, diluvialis organellar sequences were most closely related to those of S. romanzoffiana, providing evidence that the latter species is the maternal parent of S. diluvialis. The lack of genetic diversity is significant for the development of a long-term conservation strategy for S. diluvialis.