Devils Hole, a unique ecosystem in the Mojave Desert, is home to a few dominant species of algae and invertebrates as well as the endangered Devils Hole pupfish, Cyprinodon diabolis. With consistently high water temperature (33.5 °C/93 °F) and low dissolved oxygen (O₂) concentration (about 2.5 mg O₂ · L^-1), organisms are at the extremes of their physiological limits, and production of O₂ by microbial biofilms is essential to ecosystem stability. Water column O₂ concentrations were measured from July 2008 to March 2010 in the deep pool and shallow shelf habitats of Devils Hole to quantify variability in O₂ concentrations and ecosystem metabolism rates. Benthic O₂ dynamics were also measured in microbial biofilms using microelectrode surveys. Water column O₂ ranged from 2 to 6 mg O₂ · L^-1 in summers and from 1.5 to 2.2 mg O₂ — L^-1 in winter across the deep pool and shallow shelf habitats. Primary production ranged from 4 to 21 mg O₂ · L^-1d^-1, with a significant decline over the study period, potentially due to a change in the microbial biofilm community. Respiration ranged from 1.5 to 9.7 mg O₂ · L^-1d^-1 and showed a significant increase over time. Within microbial biofilms, O₂ ranged from 0 to 76 mg O₂ * L^-1. Higher concentrations of O₂ produced by these microbial biofilms may be due to improved photosynthetic efficiency under limited sunlight exposure. Autotrophic biofilms had higher O₂ concentrations during direct light exposure than during indirect light exposure. In contrast, heterotrophic biofilms had similar O₂ concentrations regardless of light exposure. Because microbial biofilms are important components of this unique ecosystem, shifts in their composition or activity may threaten ecosystem stability by reducing background O₂ concentrations below the physiological limits of the endangered Devils Hole pupfish and the entire biotic community.

Because nest predation strongly limits avian fitness, ornithologists identify nest predators to inform ecological research and conservation. During 2002–2008, we used both video-monitoring of natural nests and direct observations of predation to identify nest predators of open-cup nesting riparian songbirds along tributaries of Mono Lake, California. Video cameras at 50 nests of 3 songbird species and direct observations of additional nests confirmed 10 distinct nest-predator species and suggested one additional species. Video-monitored nests experienced reduced predation rates, and video observations mainly captured nestling predation, even though predation rates were higher for nonvideo-monitored nests during the egg period. These findings suggest cameras may have missed some predators. By supplementing video records with field observations, we reduced the likelihood of excluding species from our predator list that substantially impact fitness due to camera-related biases. No single predator species emerged as predominantly important for shaping avian fitness. Nevertheless, we frequently observed garter snakes (Thamnophis sp.) depredating nestlings and Brown-headed Cowbirds (Molothrus ater) depredating eggs. Corvids and rodents were also identified as potentially frequent groups of nest predators. Video cameras recorded partial predation by 5 predator types, as well as several cases in which nests were visited by multiple predators. Finally, 6 of 7 predators that were video-recorded depredating artificial nests were species also documented depredating natural nests. These observations verify the relevance of artificial-nest data for further study of these predators.

From 1985 to 2006, we tracked cui-ui, Chasmistes cujus, survival from potential egg deposition of migrating spawners to emigrating larvae. Tahoe sucker larvae emigrated to Pyramid Lake the same time as cui-ui larvae, but cui-ui was the predominant catostomid larvae we captured. Survival of cui-ui larvae ranged from 0.46% to 21.17%, declining significantly with decreased flow and increased number of spawners (P < 0.01). Mean total length of emigrating larvae ranged from 11.5 to 12.6 mm and may have been affected by stream flow. Removal of impediments to upstream migrating cui-ui spawners, along with sufficient stream flows, may enhance early life-stage survival.

The genus Quercus represents an important component of the scrublands and low forests of the Four Corners area of northeastern Arizona, southeastern Utah, southwestern Colorado, and northwestern New Mexico. The area is dominated by the widespread Quercus gambelii, although relictual and marginal populations of Q. turbinella and Q. havardii are also present. Hybridization among these 3 species is common, leading to much variability in phenotypic traits, and this hybridization forms part of the widespread complex of hybrid oaks recognized as Q. x undulata. Multivariate analysis of leaf morphology was performed in 9 populations, representing the various taxa and levels of hybridization. This analysis was intended to determine the distinctiveness conferred by, and extent of influence from, hybridization and successive introgression. It was found that, though common, hybridization seems to act at very restricted spatial scales and not in the production of a region-wide hybrid swarm. Most hybridization occurs between the predominant Q. gambelii and Q. turbinella. Quercus havardii appears to maintain itself as a fairly discrete taxon, with little gene exchange among congener species. Though morphological introgression actively occurs only at the local population level, it seems to have significantly altered the morphology of the parental species. This seems to be supporting evidence for extensive introgression toward the southern Q. turbinella when its distribution was more widespread. This asymmetric introgression toward Q. turbinella suggests a pattern of character coherence and the presence of a suite of advantageous traits, which may allow the species to enlarge its niche via hybridization.

The population dynamics of Sclerocactus mesae-verdae were documented annually in 3 plots over 20 years in southwestern Colorado. Demographic studies of this duration are rare but they are necessary to gain a more accurate estimate of population trends in long-lived desert species. Sclerocactus mesae-verdae was federally listed as threatened in 1979; this study was initiated in 1986 with the objective of determining whether Colorado populations were growing, declining, or stable. Data collected yearly around 1 May included diameter, vigor, and flower/fruit counts for 1629 stems belonging to 659 plants. We used regression analysis to estimate the mean, variance, and average population growth rate for each plot. Observations made throughout the study suggested that the cactus responded strongly to climatic variables, especially precipitation and temperature, and that 2 of the 3 subject populations were subject to periodic devastation by a longhorn beetle (Moneilema semipunctatum). These observations led us to attempt to correlate significant mortality (beetle-caused) or recruitment events to climate variables. We found that the cactus populations appear to be roughly stable to increasing slightly, possibly due to several wet springs and warmer-than-average winter temperatures since 1992. However, the warming trend also favors beetle predation, which overall presents a concern for the species' long-term survival. We conclude that 20 years may not be long enough to clarify large-scale climate influences on the persistence of long-lived desert species.

Fremont cottonwood (Populus fremontii) is an early successional foundation species found in riparian forest ecosystems in the North American Southwest. Along rivers, the upper limit of the seedling establishment zone depends on the proximity of seedling roots to the declining water table. The lower limit is a function of the maximum elevation of inundation or scour. Fremont cottonwood seedlings are likely to experience short-term (1- to 5-week) inundation during their first year of growth under both natural and human-influenced hydrologic regimes. Previous studies show that inundation can account for more than 70% of seedling mortality during this time. Using controlled inundation experiments, we found that seedlings of Fremont cottonwood have high tolerance of inundation to the soil surface and a reasonable tolerance of complete shoot submergence for a duration of 1 or 2 weeks (22% and 50% mortality, respectively). Mortality increased linearly with days of complete submergence (mortality percentage = 4.6 [2.5 × days of submergence]). Warm water temperature (25/18 °C day/night) during complete submergence adversely affected seedling biomass and survival, resulting in 64% mortality versus 39% with cooler water temperatures (18/11 °C day/night). Our results indicate that establishment of new Fremont cottonwood populations in the riparian corridor will be more successful when flows do not completely cover the shoots of seedlings for more than 2 weeks and if water temperatures during inundation are cool. From the perspective of the management of river flows for cottonwood recruitment, deep, prolonged, late-season (warm water) inundations are the most detrimental.

Water in the Little Colorado River within Grand Canyon is naturally high in salt (NaCl), which is known to prohibit development of external fish parasites such as Ich (Ichthyophthirius multifiliis). The naturally high salinity (>0.3%) of the Little Colorado River at baseflow may be one factor allowing survival and persistence of larval and juvenile humpback chub (Gila cypha) and other native fishes in Grand Canyon. We compared salinity readings from the Little Colorado River to those reported in the literature as being effective at removing protozoan parasites from fish. In laboratory tests, 10 juvenile roundtail chub (Gila robusta; 61–90 mm TL) were randomly placed into each of 12, 37-L aquaria filled with freshwater, water obtained from the Little Colorado River (0.3% salinity), or freshwater with table salt added until the salinity reached 0.3%. Roundtail chub was used as a surrogate for humpback chub in this study because the species is not listed as endangered but is morphologically and ecologically similar to humpback chub. All roundtail chub infected with Ich recovered and survived when placed in water from the Little Colorado River or water with 0.3% salinity, but all experimental fish placed in freshwater died because of Ich infection. The naturally high salinity of the Little Colorado River at baseflow (0.22%–0.36%), appears sufficiently high to interrupt the life cycle of Ich and may allow increased survival of larval and juvenile humpback chub relative to other areas within Grand Canyon.

We conducted a study to examine the ability of granivorous rodents to detect caches made with wildland (native and nonnative) and cultivated seeds at 3 locations in western Nevada with different vegetation types and rodent community structures. We established artificial caches containing either 2 or 3 species of wildland seeds or cultivated seeds. Five seed species were tested at each site. Under dry conditions, rodents found caches containing cultivated seeds much more rapidly than caches containing wildland seeds. Wet conditions resulted in a similar order of detectability; however, all species of seeds were located much faster in wet conditions than under dry conditions. Natural selection has likely acted on the wildland seeds to reduce their olfactory signal and potentially reduce predation upon those seeds.

While we know much about the diet of Western Burrowing Owls (Athene cunicularia hypugaea) in many of their more natural habitats, little is known about their diets in urban environments. We analyzed pellets and prey remains collected at burrows used by Burrowing Owls living in urban grasslands in Santa Clara County, California. We hypothesized that the composition of prey species in the diet of these urban owls would differ from that of owls living in agricultural and more-natural western habitats and, in particular, that rodents would be a smaller component of the diet, We found the invertebrate-to-vertebrate ratio to be approximately 94:6 by number. Orthoptera, Dermaptera, and Coleoptera were the most abundant invertebrate orders, while rodents accounted for 70% of the estimated biomass per burrow of all orders. This overall composition and these taxa are typical for Burrowing Owls in western habitats. However, Botta's pocket gopher (Thomomys bottae) was an important prey species by biomass, a species not often recorded as a dominant prey item of owls living in western habitats. The California vole (Microtus californicus) and house mouse (Mus musculus) were also dominant prey items by biomass. We recommend managing Western Burrowing Owl habitat for species, especially rodents such as pocket gophers and voles, that do well in urban habitats.

We estimated population abundance and sex ratio for a freshwater live-bearing fish species (Poeciliopsis baenschi) that inhabits fluvial systems in western Mexico. We conducted mark-recapture experiments in 6 distinct populations. We used both our catch data as well as estimates of capture probability to calculate the number of individuals per unit water volume for adult males, adult females, and juveniles. Overall, abundance varied among sites from 23.8 individuals · m^-3 to 363.2 individuals · m^-3. In most of our study sites, the estimated sex ratio was markedly biased toward females (up to 11 females per male). We discuss the potential causes and implications of the observed demographic features.

Translocation success of Greater Sage-Grouse (Centrocercus urophasianus) is generally measured by documenting whether translocated individuals survive and reproduce at the release site. However, demographic parameters, such as annual survival of translocated individuals, provide a more accurate measure of translocation success. We translocated 60 female sage-grouse from Oregon and Nevada to Clear Lake National Wildlife Refuge, California, during 2005–2010 to augment a small population of resident grouse. We radio-marked each translocated female and a sample of resident female sage-grouse, recorded their locations, and monitored their survival at monthly intervals over the study period. We observed most (55/60) translocated birds near (< 100 m from) the only lek in the study area within one week of their release. To examine factors influencing survival, we developed a set of a priori models that included the effects of translocation status, season (breeding vs. nonbreeding), year, and age on annual survival and compared the models' AIC_C values using program MARK. The null model was the best supported model and received 33% of the model weight. Models that included survival during the first year posttranslocation, age, and season, however, were competitive (<2 ΔAIC_C) with the top model. However, the β coefficient distinguishing breeding from nonbreeding season survival was the only coefficient whose 95% confidence interval did not overlap zero; monthly survival during the breeding season (0.952 ± 0.014) was lower than during the nonbreeding season (0.960 ± 0.008). The model average estimate of annual survival for female sage-grouse in our study area was 59.6% (95% CI 47.9–70.1). Our analyses provide little support for a difference in survival between translocated and resident sage-grouse, and our annual survival estimates were comparable to annual survival estimates of resident sage-grouse in other locations. Our results suggest that when current recommendations for translocation protocols are followed, translocated female sage-grouse survive just as well as resident individuals and quickly integrate into the local population.

Hispid pocket mice (Chaetodipus hispidus) are found from the grasslands of the Great Plains to the deserts of the southwestern United States, but the natural history and ecology of this species have not been described in native tallgrass prairie at the eastern edge of its range. We initiated an ongoing long-term study of small mammals on Konza Prairie Biological Station, Kansas (a Long-Term Ecological Research [LTER] site), in autumn 1981. Our sampling scheme for 14 LTER sites was a 20-station trapline; small mammals were sampled in autumn and spring for 30 years and in summer for a shorter period. We combined data for these sites with those from shorter studies on Konza Prairie that used traplines and trapping grids. We recorded only 96 hispid pocket mice over the 30 years of study (>300,000 trap-nights overall). Pocket mice were more likely to be captured in autumn and summer than in spring. The earliest annual capture was on 20 March and the latest on 7 December; males emerged from torpor in spring before females, whereas females entered torpor later in autumn. Precipitation (January—September) had a tight limiting effect on maximal number of individuals that were present in autumn. Pocket mice were more common on slope prairie than on upland or lowland prairie, but burning and grazing had no effect. Their spatiotemporal distribution showed a slightly “anti-nested” pattern with only weakly preferred sites and no focal years that might indicate favorable conditions. Collectively, our data suggested the presence of 3 age classes when individual body masses (no differences between males and females) were plotted against capture date. Finally, our study illustrates the importance of long-term data sets, especially in the study of uncommon to rare species.

Springs located on the Colorado Plateau are highly threatened and represent a small percentage of the landscape; yet they are disproportionately important to diverse native flora and fauna. The relationships between anthropogenic disturbance, aquatic macroinvertebrate species composition, and environmental variables at these springs have received little study. We selectively visited 40 sandstone springs in southeastern Utah and southwestern Colorado to span a range of impacts. We classified the springs into impact categories based on a spring impact score, and we measured biodiversity (aquatic macroinvertebrates), water chemistry (nutrients, dissolved O₂, pH, specific conductivity, temperature, turbidity, coliform bacteria [Escherichia coli]), physical characters (solar radiation, substrate, vegetation cover, bank stability, discharge), and presence of anthropogenic disturbance. Escherichia coli abundance was higher in high impact categories, and turbidity increased with increasing disturbance. No differences in total N, total P, specific conductivity, flow, dissolved O₂, pH, or substrate were found among the impact categories. Vegetation cover was higher in low impact categories than in moderate and high impact categories, while potential annual and growing-season solar radiation was lower in low impact categories than in high impact categories. Global and subsequent multiple response permutation procedure (MRPP) comparisons suggested strong differences in aquatic macroinvertebrates between low and high impact springs and no difference at moderate impact springs. Mean taxa richness (α-diversity), total taxa richness (γ-diversity), and percent of taxa richness composed of shredders peaked at moderate disturbance levels. The percentage of non-insect taxa richness was reduced in high impact categories, and Odonata (dragonflies and damselflies) were higher in low impact categories than in high impact categories. All high impact springs had both livestock use and vehicle use (roads or off-highway vehicles), and our data suggest that disturbances caused by one or both of these uses alter the aquatic macroinvertebrate assemblage. We suggest that disturbance may increase macroinvertebrate richness, where a mix of tolerant and intolerant species co-occur, until macroinvertebrate richness reaches a threshold; after surpassing this threshold, macroinvertebrate diversity decreases.

Through a phylogenetic study using LEGCYC1A nucleotide sequences and a survey of historical botanical literature, we propose clarifications in the nomenclature of Lupinus oreganus and Lupinus biddlei. The former taxon has been incorrectly classified as Lupinus sulphureus ssp. kincaidii and recently as L. oreganus var. kincaidii. The latter has recently been incorrectly delimited as L. oreganus var. oreganus.

This paper reports the first record of Eumops underwoodi in the Baja California peninsula. This record expands the species' distributional range in Mexico along the peninsula. We propose 2 plausible biogeographical explanations. First, the species has the ability to travel across the Gulf of California from the coast of Sonora to the eastern side of the Baja California peninsula and there establish. Second, there is a continuous distribution of the species throughout the mountain ranges that run longitudinally along the Baja California peninsula from the United States border down to the southern tip. We collected one male specimen of E. underwoodi in xeric-riparian habitat. We suggest a continuous distribution pattern of this species along the cliffs in the Baja California peninsula.

A specimen of an adult male of the southern grasshopper mouse Onychomys torridus was collected in Punta Choros, 25 km SE of Bahía de los Angeles, Baja California, México. This record extends the species' distribution 330 km SE of the prior southernmost locality on the peninsula.