title: Taxonomic considerations in listing subspecies under the U.S. Endangered Species Act.
abstract: The U.S. Endangered Species Act (ESA) allows listing of subspecies and other groupings below the rank of species. This provides the U.S. Fish and Wildlife Service and the National Marine Fisheries Service with a means to target the most critical unit in need of conservation. Although roughly one-quarter of listed taxa are subspecies, these management agencies are hindered by uncertainties about taxonomic standards during listing or delisting activities. In a review of taxonomic publications and societies, we found few subspecies lists and none that stated standardized criteria for determining subspecific taxa. Lack of criteria is attributed to a centuries-old debate over species and subspecies concepts. Nevertheless, the critical need to resolve this debate for ESA listings led us to propose that minimal biological criteria to define disjunct subspecies (legally or taxonomically) should include the discreteness and significance criteria of distinct population segments (as defined under the ESA). Our subspecies criteria are in stark contrast to that proposed by supporters of the phylogenetic species concept and provide a clear distinction between species and subspecies. Efforts to eliminate or reduce ambiguity associated with subspecies-level classifications will assist with ESA listing decisions. Thus, we urge professional taxonomic societies to publish and periodically update peer-reviewed species and subspecies lists. This effort must be paralleled throughout the world for efficient taxonomic conservation to take place.
authors.affiliation: USGS Forest and Rangeland Ecosystem Science Center, 3200 SW Jefferson Way, Corvallis, OR 97331, USA. susan_haig@usgs.gov
authors.forename: Susan M
authors.initials: SM
authors.lastname: Haig
authors.forename: Erik A
authors.initials: EA
authors.lastname: Beever
authors.forename: Steven M
authors.initials: SM
authors.lastname: Chambers
authors.forename: Hope M
authors.initials: HM
authors.lastname: Draheim
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Dugger
authors.forename: Susie
authors.initials: S
authors.lastname: Dunham
authors.forename: Elise
authors.initials: E
authors.lastname: Elliott-Smith
authors.forename: Joseph B
authors.initials: JB
authors.lastname: Fontaine
authors.forename: Dylan C
authors.initials: DC
authors.lastname: Kesler
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Knaus
authors.forename: Iara F
authors.initials: IF
authors.lastname: Lopes
authors.forename: Pete
authors.initials: P
authors.lastname: Loschl
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Mullins
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Sheffield
mesh_terms: D000818:Animals; D002965:Classification; D003247:Conservation of Natural Resources / Q000331:legislation & jurisprudence* / Q000379:methods; D017753:Ecosystem; D053476:Extinction, Biological; D033161:Government Regulation; D010802:Phylogeny; D013045:Species Specificity; D014481:United States