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
SREL Reprint #3032
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.
