The Nature Conservancy San Francisco

The Nature Conservancy San Francisco

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Richmond J.Q.,U.S. Geological Survey | Wood D.A.,U.S. Geological Survey | Westphal M.F.,U.S. Bureau of Land Management Marina | Vandergast A.G.,U.S. Geological Survey | And 4 more authors.
Molecular Ecology | Year: 2017

Genomic responses to habitat conversion can be rapid, providing wildlife managers with time-limited opportunities to enact recovery efforts that use population connectivity information that reflects predisturbance landscapes. Despite near-complete biome conversion, such opportunities may still exist for the endemic fauna and flora of California's San Joaquin Desert, but comprehensive genetic data sets are lacking for nearly all species in the region. To fill this knowledge gap, we studied the rangewide population structure of the endangered blunt-nosed leopard lizard Gambelia sila, a San Joaquin Desert endemic, using restriction site-associated DNA (RAD), microsatellite and mtDNA data to test whether admixture patterns and estimates of effective migration surfaces (EEMS) can identify land areas with high population connectivity prior to the conversion of native xeric habitats. Clustering and phylogenetic analyses indicate a recent shared history between numerous isolated populations and EEMS reveals latent signals of corridors and barriers to gene flow over areas now replaced by agriculture and urbanization. Conflicting histories between the mtDNA and nuclear genomes are consistent with hybridization with the sister species G. wislizenii, raising important questions about where legal protection should end at the southern range limit of G. sila. Comparative analysis of different data sets also adds to a growing list of advantages in using RAD loci for genetic studies of rare species. We demonstrate how the results of this work can serve as an evolutionary guidance tool for managing endemic, arid-adapted taxa in one of the world's most compromised landscapes. © 2017 John Wiley & Sons Ltd.

Mierau D.W.,California Trout Arcata | Trush W.J.,Humboldt State University | Rossi G.J.,University of California at Berkeley | Carah J.K.,The Nature Conservancy San Francisco | And 2 more authors.
Freshwater Biology | Year: 2017

In Mediterranean-type river systems, naturally low seasonal stream flows are often overexploited, which has implications for managing flows for environmental as well as human needs. Traditional approaches to instream flow management are not well suited to unregulated systems with strong seasonal patterns of water availability and many water diverters, and are challenging to implement in such systems. They often do not protect the full range of variability in the annual hydrograph, require extensive site-specific data, expensive modelling or both. In contrast, holistic flow management strategies, such as percent-of-flow (POF) strategies are designed to protect multiple ecological processes and preserve inter-annual flow variability. However, POF approaches typically require real-time streamflow gauging, and often lack a robust metric relating a diversion rate to ecological processes in the stream. To address these challenges, we present a modified percent-of-flow (MPOF) diversion approach where diversions are allocated from a streamflow baseline which is derived from a regional relationship between a conservative streamflow-exceedance and date. The streamflow baseline remains the same from year to year, and is independent of water-year type. This approach protects inter-annual flow variability and provides a predictable daily allowable volume of diversion at any diversion point-supporting efficient water management planning. The allowable diversion rate in the MPOF approach is based not on a fixed percentage of the ambient streamflow, but rather on a maximum allowable percentage change in riffle crest thalweg depth, an ecologically meaningful, common hydraulic measurement. In this paper, we demonstrate that the MPOF approach is a holistic approach well suited to manage diversions in unregulated streams typical of California's Mediterranean-type coastal drainages. © 2017 John Wiley & Sons Ltd.

Boser C.L.,The Nature Conservancy San Francisco | Hanna C.,California State University, Channel Islands | Holway D.A.,University of California at San Diego | Faulkner K.R.,National Park Service | And 6 more authors.
Journal of Applied Entomology | Year: 2017

The Argentine ant (Linepithema humile) is a widespread, abundant and ecologically disruptive invader that is present throughout major portions of coastal California and on half of the California Channel Islands. On Santa Cruz Island, the Argentine ant had invaded about 2% of the island's area in four distinct locations as of 2012. Given the negative ecological effects resulting from Argentine ant invasions, we sought to develop a cost-effective method of eradication. Here, we describe the results of large-scale, field-tested methods for Argentine ant eradication and post-treatment detection. Our eradication protocol employs a novel toxicant-delivery system: an aqueous solution of sucrose and 6 ppm of thiamethoxam mixed with hydrating polyacrylamide beads. Ants feed on the solution present on the bead's surface for about 24 h after which time bead dehydration prevents feeding. We distributed hydrated beads by helicopter over 74 ha of infested areas plus a 50-m buffer on 14 occasions between June 2013 and September 2014. Treatments reduced Argentine ant activity to subdetectable levels within four months. In 2014, we conducted a high-intensity detection protocol using lures (n = 55 363) in areas treated in 2013. This effort did not detect Argentine ants. In 2015, we conducted a medium-intensity detection protocol using lures (n = 2250) in areas treated in 2013 and 2014 but not searched in 2014; this sampling effort did not detect Argentine ant activity except for a single remnant infestation (c. 0.3 ha in area), which was retreated in 2015. The cost of treatments was approximately $1400 per ha; this cost is comparable to other ant eradication efforts. The cost of our preferred detection method, which used lures spaced every 10 m, was $500 per ha. These results demonstrate sufficient protocol efficacy to justify expansion of treatments to other infested areas in ecologically sensitive areas. © 2017 Blackwell Verlag GmbH.

Grantham T.E.,University of California at Berkeley | Fesenmyer K.A.,Trout Unlimited Boise | Peek R.,University of California at Davis | Holmes E.,University of California at Davis | And 6 more authors.
Conservation Letters | Year: 2016

Population growth and increasing water-use pressures threaten California's freshwater ecosystems and have led many native fishes to the brink of extinction. To guide fish conservation efforts, we provide the first systematic prioritization of river catchments and identify those that disproportionately contribute to fish taxonomic diversity. Using high-resolution range maps of exceptional quality, we also assess the representation of fish taxa within the state's protected areas and examine the concordance of high-priority catchments with existing reserves and among distinct taxonomic groups. Although most of the state's native fishes are found within protected areas, only a small proportion of their ranges are represented. Few high-priority catchments occur within protected areas, suggesting that fish conservation will require active management and targeted river restoration outside of reserves. These results provide the foundation for systematic freshwater conservation planning in California and for prioritizing where limited resources are allocated for fish recovery and protection. © 2016 Wiley Periodicals, Inc.

Reiter M.E.,Point Blue Conservation Science 3820 Cypress Drive and 11 Petaluma | Elliott N.,Point Blue Conservation Science 3820 Cypress Drive and 11 Petaluma | Veloz S.,Point Blue Conservation Science 3820 Cypress Drive and 11 Petaluma | Jongsomjit D.,Point Blue Conservation Science 3820 Cypress Drive and 11 Petaluma | And 3 more authors.
Journal of the American Water Resources Association | Year: 2015

We used Landsat satellite imagery to (1) quantify the distribution of open surface water across the Central Valley of California 2000-2011, (2) summarize spatio-temporal variation in open surface water during this time series, and (3) assess factors influencing open surface water, including drought and land cover type. We also applied the imagery to identify available habitat for waterbirds in agriculture. Our analyses indicated that between 2000 and 2011 open surface water has declined across the Central Valley during the months of July-October. On average, drought had a significant negative effect on open surface water in July, September, and October, though the magnitude and timing of the effect varied spatially. The negative impact of a drought year on open water was experienced immediately in the southern Central Valley; however, there was a one year time-lag effect in the northern Central Valley. The highest proportion of open surface water was on agricultural lands followed by lakes, rivers, and streams, yet the relative proportions varied spatially and across months. Our data were consistent with previous descriptions of waterbird habitat availability in post-harvest rice in the northern Central Valley. Tracking water distribution using satellites enables empirically based assessments of the impacts of changing water policy, land-use, drought, climate, and management on water resources. © 2015 American Water Resources Association.

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