May 21 2021
Botanists have probably described and named 99% of the plants native to the New York City metropolitan area, but there are a few surprises left. It is therefore with great pleasure that I introduce you to Spiranthes bightensis (Atlantic ladies’ tresses), a new and rare orchid I recently described, and that only occurs along the coast of the Atlantic Ocean, from Long Island, New York, to the eastern shore of Virginia.
Spiranthes are known as the ladies’ tresses orchids due to the spiraled arrangement of the flowers which resemble braided hair. Spiranthes have a reputation for being difficult to identify because the flowers are small (under 1 cm long), many of the species look remarkably similar (what botanists call “cryptic”), and many of the species also hybridize with each other. Integrating new molecular phylogenetic methods with traditional specimen-based study allows botanists to gain new insights into the diversity of plants, particularly in challenging genera like Spiranthes.
After studying Spiranthes for the last 10 years, examining thousands of herbarium specimens, and sequencing portions of their DNA, I found evidence to support the description of a new species, Spiranthes bightensis, that evolved via the ancient hybridization of S. cernua and S. odorata. In plants, hybridization is a frequent way for new species to evolve. Within Spiranthes, nearly one quarter of the species evolved via hybridization of two other species.
Spiranthes bightensis has stolons (creeping underground stems) and fragrant flowers, like S. odorata, however the shape of its flowers and column (modified stigma and anther) are very similar to S. cernua. The leaves are much longer and wider than S. cernua, but smaller than S. odorata. Additionally, DNA from the chloroplasts of these plants match the chloroplast DNA of S. cernua, but some of the DNA from the nucleus matches nuclear DNA of S. odorata.
By combing digitized herbarium specimens* with iNaturalist observations, I found that S. bightensis is endemic (restricted) to a narrow region of the Mid-Atlantic coast (technically named the Mid-Atlantic Bight), and that it has likely undergone a range-wide population collapse. Two results of this collapse are that it may now only be found in a few locations and it may be locally extinct within New York State. By naming this new species and distinguishing it from S. cernua and S. odorata, it is my hope that we can devise conservation protocols for this beautiful rare species.
The next time you are exploring a coastal natural area on Long Island, New Jersey, Delaware, and Eastern Maryland and Virginia, be on the lookout for the large and beautiful white spires Spiranthes bightensis. This species blooms in September and October and likes to grow in dune swales and other marshy areas. Of course, take only pictures, but be sure to enjoy one of the Mid-Atlantic regions’ rarest endemic species.
