SREL Reprint #3032

Sequencing Re-defines Spiranthes Relationships, with Implications for Rare and Endangered Taxa

Lucy A. Dueck¹ and Kenneth M. Cameron²
¹Savannah River Ecology Laboratory, University of Georgia, Aiken, South Carolina 29802, USA
²The New York Botanical Garden, Bronx, NY 10458-5126, USA

Introduction:
Species delimitation in the genus Spiranthes L.C. Richard (Spiranthinae, Cranichideae, Orchidoideae) has long been problematic, due mainly to morphological polymorphism confounded by hybridization and polyploidy, particularly in the S. cernua (L.) Rich. species complex (Correll 1950, Luer 1975, Sheviak 1982). Official records indicate that 462 taxa names have been used for Spiranthes historically (RBG-Kew 2006), but less than a tenth of those are recognized today, and there is still concern about the species status of some. Although Spiranthes is considered to have a worldwide distribution, only eight of these occur outside of temperate North America.

All 26 currently recognized Spiranthes taxa in the Flora of North America (Sheviak & Brown 2002) have some form of conservation listing in a U.S. state (except S. casei var. novascotiae Catling, found only in Canada), due mainly to tenuous occurrence at the edge of their range in those locations. The less-serious listing denominations include: Exploitatively Vulnerable, Rare, Sensitive, and Special Concern. Two unrecognized taxa are other exceptions - S. amesiana (either extirpated or a synonym for S. torta [Thunb.] Garay & H.R.Sweet) is Proposed Endangered by Florida due to endemicity and rarity, and newly described S. sylvatica P.M.Brown (Brown 2001a) has not been listed by any state.

Most of these Spiranthes taxa are also federally or state-listed as Threatened, Proposed Endangered, or
Endangered. However, some taxa, such as those endemic to or now limited to one or few locations, should be targeted for special protection. These include: S. brevilabris Lindl., S. delitescens Sheviak, S. eatonii Ames ex P.M.Br., S. floridana (Wherry) Cory, S. infernalis Sheviak, S. parksii Correll, and S. torta. Federally threatened S. diluvialis Sheviak is not endemic to one area, but rare throughout its range and unusual as an allopolyploid. Other taxa that can also be identified as genetically important as well as rare should be targeted for maintenance of biodiversity.

Molecular genetic techniques can provide a suite of markers from which to choose the scale of taxonomic discrimination required (Soltis & Soltis 1998, Soltis & Gitzendanner 1998, Avise 2004). Nucleotide sequencing, particularly of several genes in combination, is successfully used to address issues of phylogenetics and species delimitation, critical when conservation resources to protect threatened and endangered taxa must be focused. It is thus our goal in determining phylogenetic relationships among Spiranthes through sequence analysis to help identify these unique taxa and verify the taxonomic status of the endemic group members. Circumscribing the genetic individuality of these species of concern is a basic foundation on which to build further conservation efforts.

Key Words: conservation genetics, endangered species, polyploidy, sequencing, Spiranthes

Dueck, L. A. and K. M. Cameron. 2007. Sequencing Re-defines Spiranthes Relationships, with Implications for Rare and Endangered Taxa. Lankesteriana 7(1-2):190-195.