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USGS2018

Trends in nonindigenous aquatic species richness in the United States reveal shifting spatial and temporal patterns of species introductions

Understanding the spatial and temporal dynamics underlying the introduction and spread of nonindigenous aquatic species (NAS) can provide important insights into the historical drivers of biological invasions and aid in forecasting future patterns of nonindigenous species arrival and spread. Increasingly, public databases of species observation records are being used to quantify changes in NAS distributions across space and time, and are becoming an important resource for researchers, managers, and policy-makers. Here we use publicly available data to describe trends in NAS introduction and spread across the conterminous United States over more than two centuries of observation records. Available data on first records of NAS reveal significant shifts in dominance of particular introduction patterns over time, both in terms of recipient regions and likely sources. These spatiotemporal trends at the continental scale may be subject to biases associated with regional variation in sampling effort, reporting, and data curation. We therefore also examined two additional metrics, the number of individual records and the spatial coverage of those records, which are likely to be more closely associated with sampling effort. Our results suggest that broad-scale patterns may mask considerable variation across regions, time periods, and even entities contributing to NAS sampling. In some cases, observed temporal shifts in species discovery may be influenced by dramatic fluctuations in the number and spatial extent of individual observations, reflecting the possibility that shifts in sampling effort may obscure underlying rates of NAS introduction.

Aquatic Invasions↗

USGS1986

USE OF SPACE TECHNOLOGY IN FEDERALLY FUNDED LAND PROCESSES RESEARCH IN THE UNITED STATES.

A review of the use of space technology in federally funded earth science research in the US was carried out in 1985 by the President's Office of Science and Technology Policy. Five departments and three independent agencies, representing the primary earth science research agencies in the Federal government, participated in the review. The review by the subcommittee indicated that, while there is considerable overlap in the legislated missions of the earth science agencies, most of the space-related land processes research is complementary. Summaries are provided of the current and projected uses of space technology in land processes activities within the eight Federal organizations.

Conference Paper↗

USGS2010

Seismic hazard assessment: Issues and alternatives

Seismic hazard and risk are two very important concepts in engineering design and other policy considerations. Although seismic hazard and risk have often been used inter-changeably, they are fundamentally different. Furthermore, seismic risk is more important in engineering design and other policy considerations. Seismic hazard assessment is an effort by earth scientists to quantify seismic hazard and its associated uncertainty in time and space and to provide seismic hazard estimates for seismic risk assessment and other applications. Although seismic hazard assessment is more a scientific issue, it deserves special attention because of its significant implication to society. Two approaches, probabilistic seismic hazard analysis (PSHA) and deterministic seismic hazard analysis (DSHA), are commonly used for seismic hazard assessment. Although PSHA has been pro-claimed as the best approach for seismic hazard assessment, it is scientifically flawed (i.e., the physics and mathematics that PSHA is based on are not valid). Use of PSHA could lead to either unsafe or overly conservative engineering design or public policy, each of which has dire consequences to society. On the other hand, DSHA is a viable approach for seismic hazard assessment even though it has been labeled as unreliable. The biggest drawback of DSHA is that the temporal characteristics (i.e., earthquake frequency of occurrence and the associated uncertainty) are often neglected. An alternative, seismic hazard analysis (SHA), utilizes earthquake science and statistics directly and provides a seismic hazard estimate that can be readily used for seismic risk assessment and other applications. ?? 2010 Springer Basel AG.

Pure and Applied Geophysics↗

USGS2001

Monitoring of biological diversity in space and time

Monitoring programmes are being used increasingly to assess spatial and temporal trends of biological diversity, with an emphasis on evaluating the efficiency of management policies. Recent reviews of the existing programmes, with a focus on their design in particular, have highlighted the main weaknesses: the lack of well-articulated objectives and the neglect of different sources of error in the estimation of biological diversity. We review recent developments in methods and designs that aim to integrate sources of error to provide unbiased estimates of change in biological diversity and to suggest the potential causes.

Trends in Ecology and Evolution↗

USGS2009

Spatial and temporal patterns of chronic wasting disease: Fine-scale mapping of a wildlife epidemic in Wisconsin

Emerging infectious diseases threaten wildlife populations and human health. Understanding the spatial distributions of these new diseases is important for disease management and policy makers; however, the data are complicated by heterogeneities across host classes, sampling variance, sampling biases, and the space-time epidemic process. Ignoring these issues can lead to false conclusions or obscure important patterns in the data, such as spatial variation in disease prevalence. Here, we applied hierarchical Bayesian disease mapping methods to account for risk factors and to estimate spatial and temporal patterns of infection by chronic wasting disease (CWD) in white-tailed deer (Odocoileus virginianus) of Wisconsin, USA. We found significant heterogeneities for infection due to age, sex, and spatial location. Infection probability increased with age for all young deer, increased with age faster for young males, and then declined for some older animals, as expected from disease-associated mortality and age-related changes in infection risk. We found that disease prevalence was clustered in a central location, as expected under a simple spatial epidemic process where disease prevalence should increase with time and expand spatially. However, we could not detect any consistent temporal or spatiotemporal trends in CWD prevalence. Estimates of the temporal trend indicated that prevalence may have decreased or increased with nearly equal posterior probability, and the model without temporal or spatiotemporal effects was nearly equivalent to models with these effects based on deviance information criteria. For maximum interpretability of the role of location as a disease risk factor, we used the technique of direct standardization for prevalence mapping, which we develop and describe. These mapping results allow disease management actions to be employed with reference to the estimated spatial distribution of the disease and to those host classes most at risk. Future wildlife epidemiology studies should employ hierarchical Bayesian methods to smooth estimated quantities across space and time, account for heterogeneities, and then report disease rates based on an appropriate standardization. ?? 2009 by the Ecological Society of America.

Wisconsin↗

USGS2024

Dust in the Critical Zone: North American case studies

The dust cycle facilitates the exchange of particles among Earth's major systems, enabling dust to traverse ecosystems, cross geographic boundaries, and even move uphill against the natural flow of gravity. Dust in the atmosphere is composed of a complex and ever-changing mixture that reflects the evolving human footprint on the landscape. The emission, transport, and deposition of dust interacts with and connects Critical Zone processes at all spatial and temporal scales. Landscape properties, land use, and climatic factors influence the wind erosion of soil and nutrient loss, which alters the long-term ecological dynamics at erosional locations. Once in the atmosphere, dust particles influence the amount of solar radiation reaching Earth, and interact with longwave (terrestrial) radiation, with cascading effects on the climate system. Finally, the wet and dry deposition of particles influences ecosystem structure, composition, and function over both short and long-term scales. Tracking dust particles from source to sink relies on monitoring and measurement of the geochemical composition and size distribution of the particles, space-borne and ground-based remote sensing, and dust modeling. Dust is linked to human systems via land use and policies that contribute to dust emissions and the health-related consequences of particulate loads and composition. Despite the significant influence dust has in shaping coupled natural-human systems, it has not been considered a key component of the Critical Zone. Here, we demonstrate that dust particles should be included as a key component of the Critical Zone by outlining how dust interacts with and shapes Earth System processes from generation, through transport, to deposition. We synthesize current understanding from global research and identify critical data and knowledge gaps while showcasing case studies from North America.

Earth-Science Reviews↗

USGS2023

Conserving habitat for migratory ungulates: How wide is a migration corridor?

Conserving migratory ungulates relies on the analysis of GPS collar data and associated maps of migration corridors to inform management and policy actions. Current methods for identifying migratory corridors use complex statistical models designed to account for movement uncertainty rather than estimating the amount of space required by animals to migrate. Furthermore, such methods can complicate conservation efforts by producing highly variable corridor widths and non-contiguous corridors that do not fully connect seasonal ranges. To remedy, we propose an intuitive line buffer approach for delineating individual migration corridors that is simple to implement and focuses on the functional corridor widths needed by migratory ungulates. By buffering a line that connects successive GPS locations, we can delineate individual migration corridors with consistent widths that are robust to variable parameters (GPS fix rate, travel speed, tortuosity) and provide contiguous connection between seasonal ranges. Using a combination of expert knowledge, simulation and 10-min GPS collar data collected from mule deer ( Odocoileus hemionus ) and pronghorn ( Antilocapra americana ), we suggest 400–600 m are reasonable estimates of functional migration corridor widths for individuals of those species. Synthesis and applications . Our line buffer approach is intended to simplify migration corridor delineation, improve transparency and encourage a broader discussion of functional corridor widths. These considerations help advance efforts to conserve habitat within migration corridors and prioritize conservation efforts within a single corridor or across multiple corridors.

Journal of Applied Ecology↗

USGS1968

Geology and ground-water resources of Burlington County, New Jersey

Burlington County, which lies between Trenton, Atlantic City and Camden, has an area of 827 square miles. The county is in the Atlantic Coastal Plain physiographic province, has moderate temperatures and a dependable rainfall of 44 inches per year. The area is attracting new industries and additional population. Water usage is increasing with this economic growth; 26 mgd (million gallons per day) of ground water were used in 1960. The Raritan and Magothy Formations are the most prolific producers, but the Cohansey Sand and Kirkwood Formation have a great and, as yet, untapped potential. Small to moderately large supplies have been obtained from other aquifers. The maximum average potential recharge to the ground-water reservoirs is estimated to be about 790 mgd. Presently, most of it is rejected because the aquifers are essentially full. On this basis, it is believed that ground-water supplies in Burlington County are sufficient for the foreseeable future. However, well spacing must be planned to avoid local overdevelopment.

New Jersey↗

USGS2019

Challenges in Columbia River fisheries conservation: Response to Duda et al.

The salmonid fisheries of the Columbia River Basin (CRB) have enormous socioeconomic, cultural, and ecological importance to numerous diverse stakeholders (e.g., state, federal, tribal, nonprofit), and there are a wide array of opinions and perspectives on how these fisheries should be managed. Although we appreciate Duda et al.’s commentary, it offers only one perspective of many in this context. The objective of our paper (Hand et al. 2018) was to provide justification for “the importance of social–ecological perspectives when communicating conservation values and goals, and the role of independent science in guiding management policy and practice for salmonids in the CRB”. However, we did not intend to strictly advocate for a single course of action, and the available space within our paper’s Panel 1 limited us from engaging in a thorough ecological debate.

Frontiers in Ecology and the Environment↗

USGS2015

Ecosystem consequences of changing inputs of terrestrial dissolved organic matter to lakes: current knowledge and future challenges

Lake ecosystems and the services that they provide to people are profoundly influenced by dissolved organic matter derived from terrestrial plant tissues. These terrestrial dissolved organic matter (tDOM) inputs to lakes have changed substantially in recent decades, and will likely continue to change. In this paper, we first briefly review the substantial literature describing tDOM effects on lakes and ongoing changes in tDOM inputs. We then identify and provide examples of four major challenges which limit predictions about the implications of tDOM change for lakes, as follows: First, it is currently difficult to forecast future tDOM inputs for particular lakes or lake regions. Second, tDOM influences ecosystems via complex, interacting, physical-chemical-biological effects and our holistic understanding of those effects is still rudimentary. Third, non-linearities and thresholds in relationships between tDOM inputs and ecosystem processes have not been well described. Fourth, much understanding of tDOM effects is built on comparative studies across space that may not capture likely responses through time. We conclude by identifying research approaches that may be important for overcoming those challenges in order to provide policy- and management-relevant predictions about the implications of changing tDOM inputs for lakes.

Ecosystems↗

USGS2007

Sustaining Rocky Mountain landscapes: Science, policy and management for the Crown of the Continent ecosystem

Prato and Fagre offer the first systematic, multi-disciplinary assessment of the challenges involved in managing the Crown of the Continent Ecosystem ( CCE), an area of the Rocky Mountains that includes northwestern Montana, southwestern Alberta, and southeastern British Columbia. The spectacular landscapes, extensive recreational options, and broad employment opportunities of the CCE have made it one of the fastest growing regions in the United States and Canada, and have lead to a shift in its economic base from extractive resource industries to service-oriented recreation and tourism industries. In the process, however, the amenities and attributes that draw people to this “New West” are under threat. Pastoral scenes are disappearing as agricultural lands and other open spaces are converted to residential uses, biodiversity is endangered by the fragmentation of fish and wildlife habitats, and many areas are experiencing a decline in air and water quality. Sustaining Rocky Mountain Landscapes provides a scientific basis for communities to develop policies for managing the growth and economic transformation of the CCE without sacrificing the quality of life and environment for which the land is renowned. This forthcoming edited volume focuses on five aspects of sustaining mountain landscapes in the CCE and similar regions in the Rocky Mountains. The five aspects are: 1) how social, economic, demo graphic and environmental forces are transforming ecosystem structure and function, 2) trends in use and conditions for human and environmental resources, 3) activating science, policy and education to enhance sustainable landscape management, 4) challenges to sustainable management of public and private lands, and 5) future prospects for achieving sustainable landscapes.

Idaho, Montana↗

USGS1996

Using landscape ecology to test hypotheses about large-scale abundance patterns in migratory birds

The hypothesis that Neotropical migrant birds may be undergoing widespread declines due to land use activities on the breeding grounds has been examined primarily by synthesizing results from local studies. Growing concern for the cumulative influence of land use activities on ecological systems has heightened the need for large—scale studies to complement what has been observed at local scales. We investigated possible landscape effects on Neotropical migrant bird populations for the eastern United States by linking two large—scale inventories designed to monitor breeding—bird abundances and land use patterns. The null hypothesis of no relation between landscape structure and Neotropical migrant abundance was tested by correlating measures of landscape structure with bird abundance, while controlling for the geographic distance among samples. Neotropical migrants as a group were more sensitive to landscape structure than either temperate migrants or permanent residents. Neotropical migrants tended to be more abundant in landscapes with a greater proportion of forest and wetland habitats, fewer edge habitats, larger forest patches, and with forest habitats well dispersed throughout the scene. Permanent residents showed few correlations with landscape structure and temperate migrants were associated with habitat diversity and edge attributes rather than with the amount, size, and dispersion of forest habitats. The association between Neotropical migrant abundance and forest fragmentation differed among physiographic strata, suggesting that landscape context affects observed relations between bird abundance and landscape structure. Finally, associations between landscape structure and temporal trends in Neotropical migrant abundance were counter to those observed in space. Trends in Neotropical migrant abundance were negatively correlated with forest habitats. These results suggest that extrapolation of patterns observed in some landscapes is not likely to hold regionally, and that conservation policies must consider the variation in landscape structure associations observed among different types of bird species and in physiographic strata with varying land use histories.

Ecology↗

USGS2004

Effects of housing density and cage floor space on C57BL/6J mice

The Guide for the Care and Use of Laboratory Animals (the Guide) is widely accepted as the housing standard by most Institutional Animal Care and Use Committees. The recommendations are based on best professional judgment rather than experimental data. Current efforts are directed toward replacing these guidelines with data-driven, species-appropriate standards. Our studies were undertaken to determine the optimum housing density for C57BL/6J mice, the most commonly used inbred mouse strain. Four-week-old mice were housed for 8 weeks at four densities (the recommended ???12 in2 [ca. 77.4 cm 2]/mouse down to 5.6 in2 [ca. 36.1 cm2]/mouse) in three cage types with various amounts of floor space. Housing density did not affect a variety of physiologic parameters but did affect certain micro-environmental parameters, although these remained within accepted ranges. A second study was undertaken housing C57BL/6J mice with as little as 3.2 in2/mouse (ca. 20.6 cm2). The major effect was elevated ammonia concentrations that exceeded limits acceptable in the workplace at increased housing densities; however, the nasal passages and eyeballs of the mice remained microscopically normal. On the basis of these results, we conclude that C57BL/6J mice as large as 29 g may be housed with 5.6 in2 of floor space per mouse. This area is approximately half the floor space recommended in the Guide. The role of the Guide is to ensure that laboratory animals are well treated and housed in a species-appropriate manner. Our data suggest that current policies could be altered in order to provide the optimal habitation conditions matched to this species' social needs. Copyright 2004 by the American Association for Laboratory Animal Science.

Comparative Medicine↗

USGS2003

Specification aggregate quarry expansion - A case study demonstrating sustainable management of natural aggregate resources

Many countries, provinces, territories, or states in the European Union, Australia, Canada, the United States, and elsewhere have begun implementing sustainability programs, but most of those programs stop short of sustainable management of aggregate resources. Sustainable practices do not always have to be conducted under the title of sustainability. This case study describes how Lafarge, a large multinational construction materials supplier, implemented the principles of sustainability even though there was an absence of existing local government policies or procedures addressing sustainable resource management. Jefferson County, Colorado, USA, is one of three counties in the six-county Denver, Colorado, region that has potentially available sources of crushed stone. Crushed stone comprises 30 percent of the aggregate produced in the area and plays a major role in regional aggregate resource needs. Jefferson County is home to four of the five crushed stone operations in the Denver region. Lafarge operates one of those four quarries. Lafarge recently proposed to expand its reserves by exchanging company-owned land for existing dedicated open space land adjacent to their quarry but owned by Jefferson County. A similar proposal submitted about 10 years earlier had been denied. Contrary to the earlier proposal, which was predicated on public relations, the new proposal was predicated on public trust. Although not explicitly managed under the moniker of sustainability, Lafarge used basic management principles that embody the tenets of sustainability. To achieve the goals of sustainable aggregate management where no governmental policies existed, Lafarge not only assumed their role of being a responsible corporate and environmental member of the community, but also assumed the role of facilitator to encourage and enable other stakeholders to responsibly resolve legitimate concerns regarding the Lafarge quarry proposal. Lafarge successfully presented an enlightened proposal where the county will gain 745 acres of new open space land in exchange for 60 acres of current open space land adjacent to the quarry. The process involved collaborative efforts by all stakeholders and resulted in an outcome that balances the needs of society, the environment, and business.

Colorado↗

USGS2022

Global genetic diversity status and trends: Towards a suite of Essential Biodiversity Variables (EBVs) for genetic composition

Biodiversity underlies ecosystem resilience, ecosystem function, sustainable economies, and human well-being. Understanding how biodiversity sustains ecosystems under anthropogenic stressors and global environmental change will require new ways of deriving and applying biodiversity data. A major challenge is that biodiversity data and knowledge are scattered, biased, collected with numerous methods, and stored in inconsistent ways. The Group on Earth Observations Biodiversity Observation Network (GEO BON) has developed the Essential Biodiversity Variables (EBVs) as fundamental metrics to help aggregate, harmonize, and interpret biodiversity observation data from diverse sources. Mapping and analyzing EBVs can help to evaluate how aspects of biodiversity are distributed geographically and how they change over time. EBVs are also intended to serve as inputs and validation to forecast the status and trends of biodiversity, and to support policy and decision making. Here, we assess the feasibility of implementing Genetic Composition EBVs (Genetic EBVs), which are metrics of within-species genetic variation. We review and bring together numerous areas of the field of genetics and evaluate how each contributes to global and regional genetic biodiversity monitoring with respect to theory, sampling logistics, metadata, archiving, data aggregation, modeling, and technological advances. We propose four Genetic EBVs: ( i ) Genetic Diversity; ( ii ) Genetic Differentiation; ( iii ) Inbreeding; and ( iv ) Effective Population Size ( N e ). We rank Genetic EBVs according to their relevance, sensitivity to change, generalizability, scalability, feasibility and data availability. We outline the workflow for generating genetic data underlying the Genetic EBVs, and review advances and needs in archiving genetic composition data and metadata. We discuss how Genetic EBVs can be operationalized by visualizing EBVs in space and time across species and by forecasting Genetic EBVs beyond current observations using various modeling approaches. Our review then explores challenges of aggregation, standardization, and costs of operationalizing the Genetic EBVs, as well as future directions and opportunities to maximize their uptake globally in research and policy. The collection, annotation, and availability of genetic data has made major advances in the past decade, each of which contributes to the practical and standardized framework for large-scale genetic observation reporting. Rapid advances in DNA sequencing technology present new opportunities, but also challenges for operationalizing Genetic EBVs for biodiversity monitoring regionally and globally. With these advances, genetic composition monitoring is starting to be integrated into global conservation policy, which can help support the foundation of all biodiversity and species' long-term persistence in the face of environmental change. We conclude with a summary of concrete steps for researchers and policy makers for advancing operationalization of Genetic EBVs. The technical and analytical foundations of Genetic EBVs are well developed, and conservation practitioners should anticipate their increasing application as efforts emerge to scale up genetic biodiversity monitoring regionally and globally.

Biological Reviews↗

USGS1997

Landsat Data

In the mid-1960's, the National Aeronautics and Space Administration (NASA) embarked on an initiative to develop and launch the first Earth monitoring satellite to meet the needs of resource managers and earth scientists. The U.S. Geological Survey (USGS) entered into a partnership with NASA in the early 1970?s to assume responsibility for archiving data and distributing data products. On July 23, 1972, NASA launched the first in a series of satellites designed to provide repetitive global coverage of the Earth?s land masses. Designated initially as the "Earth Resources Technology Satellite-A" ("ERTS-A"), it used a Nimbus-type platform that was modified to carry sensor systems and data relay equipment. When operational orbit was achieved, it was designated "ERTS-1." The satellite continued to function beyond its designed life expectancy of 1 year and finally ceased to operate on January 6, 1978, more than 5 years after its launch date. The second in this series of Earth resources satellites (designated ?ERTS-B?) was launched January 22, 1975. It was renamed "Landsat 2" by NASA, which also renamed "ERTS-1" as "Landsat 1." Three additional Landsats were launched in 1978, 1982, and 1984 (Landsats 3, 4, and 5 ). (See table 1). NASA was responsible for operating the program through the early 1980?s. In January 1983, operation of the Landsat system was transferred to the National Oceanic and Atmospheric Administration (NOAA). In October 1985, the Landsat system was commercialized and the Earth Observation Satellite Company, now Space Imaging EOSAT, assumed responsibility for its operation under contract to NOAA. Throughout these changes, the USGS EROS Data Center (EDC) retained primary responsibility as the Government archive of Landsat data. The Land Remote Sensing Policy Act of 1992 (Public Law 102-5555) officially authorized the National Satellite Land Remote Sensing Data Archive and assigned responsibility to the Department of the Interior. In addition to its Landsat data management responsibility, the EDC investigates new methods of characterizing and studying changes on the land surface with Landsat data.

Fact Sheet↗

USGS2019

Spatially explicit models of seasonal habitat for greater sage‐grouse at broad spatial scales: Informing areas for management in Nevada and northeastern California

Defining boundaries of species' habitat across broad spatial scales is often necessary for management decisions, and yet challenging for species that demonstrate differential variation in seasonal habitat use. Spatially explicit indices that incorporate temporal shifts in selection can help overcome such challenges, especially for species of high conservation concern. Greater sage‐grouse Centrocercus urophasianus (hereafter, sage‐grouse), a sagebrush obligate species inhabiting the American West, represents an important case study because sage‐grouse exhibit seasonal habitat patterns, populations are declining in most portions of their range and are central to contemporary national land use policies. Here, we modeled spatiotemporal selection patterns for telemetered sage‐grouse across multiple study sites (1,084 sage‐grouse; 30,690 locations) in the Great Basin. We developed broad‐scale spatially explicit habitat indices that elucidated space use patterns (spring, summer/fall, and winter) and accounted for regional climatic variation using previously published hydrographic boundaries. We then evaluated differences in selection/avoidance of each habitat characteristic between seasons and hydrographic regions. Most notably, sage‐grouse consistently selected areas dominated by sagebrush with few or no conifers but varied in type of sagebrush selected by season and region. Spatiotemporal variation was most apparent based on availability of water resources and herbaceous cover, where sage‐grouse strongly selected upland natural springs in xeric regions but selected larger wet meadows in mesic regions. Additionally, during the breeding period in spring, herbaceous cover was selected strongly in the mesic regions. Lastly, we expanded upon an existing joint–index framework by combining seasonal habitat indices with a probabilistic index of sage‐grouse abundance and space use to produce habitat maps useful for sage‐grouse management. These products can serve as conservation planning tools that help predict expected benefits of restoration activities, while highlighting areas most critical to sustaining sage‐grouse populations. Our joint–index framework can be applied to other species that exhibit seasonal shifts in habitat requirements to help better guide conservation actions.

California, Nevada↗

USGS1992

Implications of morphological variation among populations of California roach Lavinia symmetricus (Cyprinidae) for conservation policy

The California roach Lavinia symmetricus is a small cyprinid native to Central California. Populations of roach are presently isolated from one another due to degradation of stream habitats between them. We examined eight populations, each from a tributary system of the San Joaquin River, to determine if morphological differences existed among them. These tributaries are now isolated from one another by dams or areas of unsuitable habitat. We found significant differences among drainages for all of the characters studied. Discriminant analysis classified 70% of the individuals to the correct drainage. The differences were not clinal because adjacent drainages were not grouped together in discriminant space. The most distinct population was as different from a nearby population (36 stream km) as from populations from other more distant tributaries and could possibly merit subspecies status. These results suggest that each population has been isolated long enough to develop morphological adaptions to local environment conditions. With one exception, the differences among the populations were too small for formal taxonomic recognition but suggest that management should focus on preserving local populations throughout the species' range, rather than scattered populations in a few reserves. This policy would serve to protect the genetic diversity of California roach, local aquatic habitats, and other even more poorly known species.

California↗