Division Into Species and Hybrids
Since the species do not readily cross with each other, hybrids are rare in this genus.
- Spiranthes × intermedia Ames (1903) (SE. Canada to NE. U.S.A.)
- Spiranthes × itchetuckneensis P.M.Br. (1999) (Florida)
- Spiranthes × simpsonii Catling & Sheviak (1993) (SE. Canada to NC. U.S.A)
Dr. Charles Sheviak, a taxonomist with the New York State Museum, has suggested that Spiranthes delitescens is an amphiploid hybrid between two species with different chromosome numbers, possibly Spiranthes vernalis and Spiranthes porrifolia Sheviak (1990) (Arizona).
However, more complicated forms of gene flow are present in this genus. There are a number of polyploid species known as the S. cernua complex, which are characterized by apomixis and polyembryony. This complex includes S. cernua, S. parksii, and perhaps S. casei. Related species, which include at least some plants identified as S. magnicamporum, S. ochroleuca, and S. odorata, are diploids and there is gene flow from the diploids to the polyploids, but not in reverse.
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