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Anthropogenic alterations to lotic systems are often implicated in global declines among stream-dwelling fishes. A primary step toward mediating fish declines is improving our understanding of species—environment relationships; unfortunately, such information is limited. The goal of this study was to assess relationships between fish communities and environmental variables in a relatively intact portion of the Rio Grande/Rio Bravo del Norte in the southwestern United States and northern Mexico. We quantified the relationship between riverine habitats and local fish communities at 7 sites in the Big Bend reach of the Rio Grande/Rio Bravo del Norte during 2006. Monthly collections yielded 10,565 individuals representing 20 species, including 6 species listed as threatened or otherwise at risk. Species richness varied among sites (range 13–19) as did diversity (1 - D: 0.49–0.72) and density (16–45 fish · 100 m-2). Fish community composition indicated spatial and temporal variations, but habitat characteristics indicated more variation among sampling sites than among months. Spatial variation in community structure correlated with site-specific habitat characteristics, and most threatened or at risk species were associated with run or riffle geomorphic units containing higher current velocities and gravel to cobble substrates. Temporal variation in community structure correlated with fall monsoonal flooding, during which composition of dominant species shifted from the habitat generalist red shiner (Cyprinella lutrensis) to the imperiled, regionally endemic Tamaulipas shiner (Notropis braytoni). Results from this study suggest that large flood pulses and maintenance of habitat heterogeneity are necessary for the persistence of both declining and intact local fish communities in the Rio Grande/Rio Bravo del Norte.
Two prairie-clovers, Dalea ornata (Douglas ex Hook.) Eaton & J. Wright and Dalea searlsiae (A. Gray) Barneby are perennial forbs found sporadically in the U.S. Intermountain West. Their seed is desirable for use in rangeland restoration. We experimentally characterized the breeding biologies of D. ornata and D. searlsiae in a common garden, surveyed their pollinator guilds, and sampled their seed predators. The 2 Dalea species, being primarily xenogamous, have comparable pollination requirements. For flowers manually pollinated with outcross pollen, an average of 42% of D. ornata flowers and 39% of D. searlsiae flowers yielded plump large seeds filled with endosperm. Both species proved to be self-compatible, but far fewer seeds resulted from either manual pollination with self-pollen (11% seed set for D. ornata and 7% for D. searlsiae) or unassisted autogamy (5% and 6% seed set, respectively). Limited surveys of the prairie-clovers' pollinator guilds in ruderal or cheatgrass-infested habitats revealed sparse visitation solely by wild bees, primarily of the genera Anthidium, Colletes, Bombus, Eucera, and Melissodes. Beetles (Acanthoscelides oregonensis Johnson and Apion amaurum Kissinger) infested seed sampled from 18 of 25 D. ornata populations across a 3-state region. Productive farming of the seed of these prairie-clovers for rangeland restoration in the western United States will require supplementation of bees for pollination and exclusion of seed beetles.
We describe a new springsnail species, Pyrgulopsis cybele, from the Owyhee River basin (northwestern Nevada) based on morphologic and molecular (mtCOI) evidence. Pyrgulopsis cybele differs from other members of its genus in its unique pattern of penial ornament, which consists of small glands on the distal edge of the penial lobe, base of the penial filament, and outer edge of the medial section of the penis. It is further differentiated from regional congeners by its thickened inner-shell lip and mtCOI sequences. A Bayesian analysis based on COI data placed P. cybele in a well-supported clade that contained congeners from Snake River, Great Basin, Colorado River, and California Pacific Coastal drainages; the sister taxon of this new species was not resolved. The COI divergence of P. cybele relative to its most genetically similar congener (P. glandulosa) suggests that it evolved subsequent to emplacement of the Miocene basalt that carpets the upper South Fork Owyhee basin. Pyrgulopsis cybele was collected from 2 closely proximal springs along the South Fork Owyhee River below the Nevada Pipeline Crossing. Although these populations are in a remote wilderness study area, they may be threatened by livestock grazing and human disturbance.
Surveys for foliar ozone injury on cutleaf coneflower, spreading dogbane, and quaking aspen were conducted in Rocky Mountain National Park, Colorado, from 2006 through 2010. Foliar injury in the form of ozone stipple was found on coneflower each year. The incidence of injured plants on sites with injury ranged from 5% to 100%. The severity of injury on affected foliage was generally <4% but occurred on some leaves at a level greater than 12% in 3 years and in 1 year on 1 plant at a level >75%. No foliar ozone injury was found on spreading dogbane or quaking aspen in any year of the survey. This is the first documentation of ozone injury on vegetation in Rocky Mountain National Park. While ozone has long been a concern in the Colorado Front Range, spreading urbanization and oil and gas development are leading to increased levels of ozone in many areas in the Rocky Mountain region. Air monitoring data indicate that ozone exposures are exceeding injury thresholds in several locations and suggest that assessments of foliar ozone injury should be conducted on ozone-sensitive plant species in riparian and moist communities in those areas.
Quantifying an invasive species' negative impacts across its introduced range will be quite challenging if the impacts vary unpredictably from site to site or from population to population. Little emphasis, however, has been placed on quantifying such interpopulation variation in the impacts of individual invasive species. We studied the response of a native grass (Festuca rubra) to competition from 4 geographically dispersed invasive plant (Melilotus albus) populations in order to determine if some populations of this invader have greater competitive impacts than others. Despite the relatively large number of experimental units in our greenhouse study, we did not obtain evidence that competitive effects per gram of biomass varied by invader population. Therefore, in some cases it should be possible to estimate the effects of invasive weeds with simple competition models that ignore some forms of phenotypic variation, as long as the models control for invader biomass per unit area (i.e., invader yield).
Groundwater-dependent ecosystems (GDEs) that do not meet the legal definition of wetlands are important for sustaining regional biodiversity, livestock grazing, and outdoor recreation in the Intermountain West. Such GDEs in Owens Valley, California, are also used to produce 11,225 hectare meters (91,000 acre-feet) of water annually from about 100 water wells. We used 21 years of Landsat data and 18 years of field monitoring data to analyze responses of 2 adjacent-meadow GDEs to different groundwater management practices. The northern meadow, which was subject to continuous water table drawdown below the rooting zone of phreatophytic grasses, experienced decline in total live cover from 42.7% to 30.2%, decline in grass cover from 27.5% to 14.1%, transition from grass to shrub dominance, and change from groundwater dependence to precipitation dependence. These responses had been predicted by managers in 1976. The southern meadow, which was managed with cycles of water table drawdown and recovery, experienced neither cover decline nor dominance-type conversion and remained groundwater dependent. Variation in depth-to-water table (DTW) explained 83% of the pooled variance in total live cover in both meadows. Results showed that nonwetland, nonriparian GDEs are vulnerable to water table decline, as are wetland and riparian GDEs. Managing groundwater extraction through imposing one- to several-year cycles of water table drawdown and recovery may avoid further cover decline and type conversion in GDEs already affected by groundwater withdrawals.
The faunal assemblage from Five Finger Ridge, an archaeological site in central Utah that was occupied by the Fremont from approximately AD 1100 to 1350, shows marked transitions in the relative abundances of 3 leporid taxa. At the time of initial occupation of the site, Sylvilagus audubonii and Lepus sp. dominated the assemblage but through time were gradually replaced by Sylvilagus nuttallii. I contextualized the shifting frequencies of these species using independent paleovegetation data. The data collectively suggest that the altitudinal range of the leporid species shifted during occupation of the site as a response to expanding pinyon-juniper woodlands.
The longnose gar (Lepisosteus osseus) is a primitive predaceous fish common throughout much of the east central United States, but research on its age and growth in lacustrine systems is rare. To characterize gar age and growth, I used bowfishing to collect spawning longnose gar in spring 2010 from littoral zones at Lake Arrowhead, Clay County, Texas. Females were older than males but significantly exceeded males in total length and mass when age was controlled. Von Bertalanffy growth curves suggested that males had faster growth rates, smaller maximum lengths, and shorter life spans than did females. However, females were always longer than males at any given age. Bowfishing capture beyond distances of 9 m was biased toward larger fish, but the method was viable for collecting spawning longnose gar at close range. This study will assist fisheries managers and aquaculturists by providing growth—age relationships for longnose gar in a southern lacustrine system.
To compensate for losses in overwintering habitat, elk are fed hay in winter at approximately 37 locations throughout the western United States. These winter feeding programs concentrate elk activity, and there is concern that such concentrations could degrade plant communities. Except for one study focused exclusively on aspen (Populus tremuloides), ours is the first to quantify vegetation responses to supplemental winter feeding of elk. The western Wyoming feedground we studied was established in winter 1981–1982, and supplemental feeding occurred every winter through 2006. Transects were arranged in a before-after control-impact (BACI) design, and vegetation data were gathered in the midsummers of 1981 and 2006. Over the study period, the feedground became invaded by smooth brome (Bromus inermis), a nonnative grass constituent of hay fed to the elk. The smooth brome invasion was attended by declines in native forb cover and the apparent extirpation of shrubs from the feedground. The smooth brome invasion did not extend beyond the feedground, but an area 125 m from the feedground showed decreases in shrubs. At areas ≥750 m from the feedground, forbs and shrubs did not decrease demonstrably, and in some cases they showed evidence of increasing over the study period. Supplemental winter feeding at a feedground in western Wyoming degraded the plant community, but, with the possible exception of aspen, the degradation did not appear to extend great distances beyond the small area where the animals were fed.
Mosses may compete with vascular plants for limited soil resources, facilitate vascular plants by buffering extremes in abiotic conditions, and potentially trap seeds and provide safe sites for germination and establishment. We conducted a field study to investigate the effects of moss on the distribution and performance of Primula cusickiana var. maguirei, a threatened endemic perennial forb that occurs in an extremely narrow range within a single canyon in northern Utah, USA. Within the study population, we found that primroses occurred far more often on moss patches than on other substrates and that primroses occurring on moss patches had increased basal area and flower production. Furthermore, analyses revealed that soil under moss patches with primrose present had more organic matter, elevated magnesium concentrations, and lower Ca:Mg ratios. Our results suggest at least 3 hypotheses that may be evaluated through future studies. First, moss may facilitate P. cusickiana var. maguirei via the provision of increased soil resources. Second, moss may trap primrose seeds, leading to the observed pattern of distribution. and third, mosses and the primrose may both be responding to an as-yet-unmeasured habitat factor (e.g., soil depth or microtopography). Our results inform future research on P. cusickiana var. maguirei and have direct implications for the conservation of this threatened species.
I report one new record for the threatened Mexican hairy porcupine (Coendou mexicanus) and 5 new records for the threatened tamandua (Tamandua mexicana) in northern Puebla, Mexico. Although additional distributional data is needed, the existence of populations in this area could be important for the conservation and management of these species in the region.
We report details of a serendipitous encounter in July 2010 with a gopher snake (Pituophis catenifer) hunting in the mud nests of Cliff Swallows (Petrochelidon pyrrhonota). The swallow nests occurred beneath a deeply overhung sandstone cliff ledge in a box canyon of Ferron Creek in the shale deserts near Ferren, Emery County, Utah. The inaccessibility of the nests and the movement of the snake to and through them attest to both the extraordinary climbing ability of the gopher snake and the nest site selection and nest construction ability of the swallows.
Tibicen pruinosus (Say)—a large, arboreal cicada typically found in the central United States—is reported for the first time from Colorado. This new state record represents a significant western extension of this cicada's known range. Also reported are new records from Kansas that link the Colorado population to the previously known distribution of T. pruinosus. These results suggest that T. pruinosus has expanded its range westward, likely facilitated by human-induced changes in vegetation on the Great Plains. They also indicate the effectiveness of acoustic surveys as a tool for studying cicada distributions. Finally, an updated key including all 7 species of Tibicen now known from Colorado is provided.
Hantavirus pulmonary syndrome (HPS) is a rare disease with a high mortality rate, caused by New World viral species of the genus Hantavirus. The presence of hantaviruses both north and south of Mexico suggests an extended presence through the country. Our objective was to conduct serologic tests to detect antibodies against hantaviruses in wild rodents of the tropical deciduous forest in Morelos, Mexico, and to report information about the distribution and prevalence of these viruses. Blood samples from 153 cricetid and heteromyid rodents were tested for immunoglobulin G (IgG) antibodies. One individual of Liomys irroratus was seropositive for a Hantavirus antigen. Our results suggest that hantaviruses occur in rodents from southern Morelos in central Mexico. Given the possibility of a false positive result, it is important that this finding be validated with further research.