Decisions under the U.S. Endangered Species Act (ESA) require scientific input on the risk that the species will become extinct. A series of critiques on the role of science in ESA decisions have called for improved consistency and transparency in species risk assessments and clear distinctions between science input and policy application. To address the critiques and document the emerging practice of the U.S. Fish and Wildlife Service (USFWS), we outline an assessment process based on principles and practices of risk and decision analyses that results in a scientific report on species status. The species status assessment (SSA) process has three successive stages: 1) document the life history and ecological relationships of the species in question to provide the foundation for the assessment, 2) describe and hypothesize causes for the current condition of the species, and 3) forecast the species' future condition. The future condition refers to the ability of a species to sustain populations in the wild under plausible future scenarios. The scenarios help explore the species' response to future environmental stressors and to assess the potential for conservation to intervene to improve its status. The SSA process incorporates modeling and scenario planning for prediction of extinction risk and applies the conservation biology principles of representation, resiliency, and redundancy to evaluate the current and future condition. The SSA results in a scientific report distinct from policy application, which contributes to streamlined, transparent, and consistent decision-making and allows for greater technical participation by experts outside of the USFWS, for example, by state natural resource agencies. We present two case studies based on assessments of the eastern massasauga rattlesnake Sistrurus catenatus and the Sonoran Desert tortoise Gopherus morafkai to illustrate the process. The SSA builds upon the past threat-focused assessment by including systematic and explicit analyses of a species' future response to stressors and conservation, and as a result, we believe it provides an improved scientific analysis for ESA decisions.

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We used allozyme electrophoresis to quantify genetic variation in nine populations of the Gammarus pecos species complex endemic to spring systems of the northern Chihuahuan Desert. There was significant within-population and high among-population genetic variation. Two populations exhibited heterozygote deficiencies and high proportions of polymorphic loci, which suggests the presence of cryptic species. Genetic distances among populations were negatively correlated with previously published morphological similarities, which suggests congruence between allozyme and morphological phenotypes. Cluster analysis of genetic distances showed four major groups of populations within the G. pecos complex. Genetic identities and fixed allelic differences support the presence of at least four distinct species: Gammarus desperatus, G. pecos, Gammarus hyalleloides, and one or more undescribed species. Relatively large genetic distances between populations suggest long periods of isolation and allopatric speciation. Patterns of among-population genetic variation were similar between amphipods and several groups of endemic fishes and snails, which suggests a coherence to biogeographic patterns within this region. Thus, the understanding of the genetic structure and taxonomic status of the G. pecos species complex provides insight into the biogeography of other aquatic organisms in the northern Chihuahuan Desert. Given the alarming rate at which desert spring systems are being altered and the unique biotic assemblages present, protection of these habitats is imperative.In desert regions, springs have long been considered to be unlimited sources of water for a variety of human activities. The habitat destruction resulting from such activities is an especially severe problem when it affects regions of high endemism, where most endangered species are found (Dob-

At least one-third of all amphibian species face the threat of extinction, and current amphibian extinction rates are four orders of magnitude greater than background rates. Preventing extirpation often requires both ex situ (i.e., conservation breeding programs) and in situ strategies (i.e., protecting natural habitats). Flatwoods salamanders (Ambystoma bishopi and A. cingulatum) are protected under the U.S. Endangered Species Act. The two species have decreased from 476 historical locations to 63 recently extant locations (86.8% loss). We suggest that recovery efforts are needed to increase populations and prevent extinction, but uncertainty regarding optimal actions in both ex situ and in situ realms hinders recovery planning. We used structured decision making (SDM) to address key uncertainties regarding both captive breeding and habitat restoration, and we developed short-, medium-, and long-term goals to achieve recovery objectives. By promoting a transparent, logical approach, SDM has proven vital to recovery plan development for flatwoods salamanders. The SDM approach has clear advantages over other previous approaches to recovery efforts, and we suggest that it should be considered for other complex decisions regarding endangered species.

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