A comparison of epiphytic diatom assemblages on living and dead stems of the common grass Phragmites australis

Diatoms epiphytic on Phragmites australis (Cav.) Trin. ex Steaded stems were collected from a single clone at the southern end of Provo Bay, Utah Lake, Utah. Diatom populations from both living and dead stem sections were analyzed. Species diversity in each sample was high, indicating that the stems provide a relatively stable habitat for diatom epiphytes. Of the 23 genera found, only Gomphonema and Navicula showed significant trends toward stem preference. The diatoms in this study support the current view that Utah Lake is a slightly saline, eutrophic system.     

Diversification within the Mexican vole ( Microtus mexicanus ) and the role of post-Pleistocene climate change

Normal 0 false false false MicrosoftInternetExplorer4 st1\:*{behavior:url(#ieooui) } /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} To examine the partitioning of genetic variation within the Mexican vole ( Microtus mexicanus ), we analyzed variation within the cytochrome b (cyt b, ca. 953 bp) from 44 samples of the Mexican vole from the mountains of the southwestern United States and Mexico. Phylogeographic analyses demonstrated strong support for a western clade and an eastern clade, corresponding to the Sierra Madre Occidental and mountains of the southwestern United States (western clade) and the Sierra Madre Oriental and the Sierra Madre del Sur (eastern clade). Levels of genetic distinctiveness among vole populations in Mexico and the southwestern United States support recognition of the Mogollon vole ( Microtus mogollonensis ). Estimates of lineage divergence suggested an older divergence for populations in Mexico and a more recent divergence for the presumptive M. mogollonensis. Ecological analyses demonstrated a distinct climate niche between vole lineages in the Southwest and Mexico, which indicated the possible role of environmental variation in diversification of the Mexican vole. A similar pattern of climatic separation was also demonstrated between clades of the codistributed taxa Sigmodon hispidus, Neotoma mexicana, and Peromyscus truei, suggesting a broader role for climatic variation in the origin and maintenance of the region’s biodiversity. Para examinar la distribución de la variación genética en el metorito mexicano, analizamos la variación en el citocromo b (cyt b, c. 953 pb ) en 44 muestras del metorito mexicano de las montañas de México y del suroeste de Estados Unidos. Los análisis filogeográficos demostraron fuerte apoyo para un clado occidental y un clado oriental, correspondientes a la Sierra Madre Occidental y las montañas del suroeste de Estados Unidos (oeste) y la Sierra Madre Oriental y la Sierra Madre del Sur (este). Los niveles de diferencia genética entre las poblaciones de metoritos en México y las del sur de Estados Unidos apoyan el reconocimiento del metorito Mogollon ( Microtus mogollonensis ) como especie. Las estimaciones de divergencia entre linajes indican una divergencia más remota para las poblaciones en México y una más reciente para el presunto M. mogollonensis. Los análisis ecológicos demuestran nichos climáticos distintos entre los linajes de metorito en el suroeste de Estados Unidos y en México, lo cual indica el posible papel de la variación ambiental en la diversificación del metorito mexicano. Un patrón similar de separación climática fue también demostrado entre clados de los taxones codistribuidos: Sigmodon hispidus, Neotoma mexicana y Peromysus truei, sugiriendo que la variación climática tiene un mayor papel en el origen y el mantenimiento de la biodiversidad de la región.     

Exercise conditioning decreases downstream movement of pond-reared razorback suckers released into a stream environment

Despite augmentation stocking efforts, wild populations of razorback suckers ( Xyrauchen texanus ) continue to decline. Endangered razorback suckers are commonly raised in off-channel ponds until maturity (approximately 300 mm TL) and then stocked into the Colorado River or its tributaries. After fish are stocked, they commonly move large distances downstream. We conducted an experiment to determine if downstream dispersal could be reduced through exercise conditioning. Two groups of razorback suckers, exercised and nonexercised, were released into Fossil Creek, Arizona. Prior to release, a subsample from each treatment group was tested in a laboratory flow chamber. Razorback suckers that had been exercise conditioned were able to maintain a position in the flow chamber 2 times longer and at velocities 25 cm · s –1 higher than nonexercised fish. Although the intended method of field data collection via passive-integrated-transponder (PIT) antennas and a remote communication station failed because river otters ( Lontra canadensis ) preyed upon the released razorback suckers, implanted PIT tags were retained in otter scat. Recovered PIT tags enabled distributional analysis, which indicated that exercised razorback suckers did not move as far downstream from the point of release as nonexercised razorbacks. Exercise conditioning may increase overall fitness of pond-reared razorback suckers, and, consequently, increase the effectiveness of augmentation stocking. A pesar de los esfuerzos de repoblación, las poblaciones silvestres del matalote jorobado ( Xyrauchen texanus ) siguen en declive. Los matalotes jorobados, que están en peligro de extinción, se crían en estanques fuera del cauce hasta la etapa adulta (~300 mm) y después son liberados en el Río Colorado o uno de sus afluentes. Los peces suelen desplazarse largas distancias río abajo después de su introducción al río. Llevamos a cabo un experimento para determinar si la dispersión río abajo se podía reducir mediante el acondicionamiento por ejercicio. Dos grupos de matalotes fueron liberados en Fossil Creek, Arizona, uno que había sido acondicionado y otro que no. Antes de liberarlos, examinamos una submuestra de cada grupo en una cámara de flujo en el laboratorio. Los matalotes que habían sido acondicionados por ejercicio pudieron mantener sus posición en la cámara de flujo dos veces más tiempo y a velocidades de 25 cm · s –1 más altas que los peces no acondicionados. Aunque falló el método de colecta de datos mediante antenas de sistema PIT (passive integrated transponder) y una estación remota de comunicación, los matalotes liberados fueron depredados por nutrias de río ( Lontra canadensis ) y las marcas PIT implantadas se quedaron en las heces de las nutrias. La recuperación de estas etiquetas PIT permitió un análisis de distribución que indicó que los matalotes acondicionados no se desplazaron río abajo tan lejos del punto de liberación como los matalotes no acondicionados. El acondicionamiento por ejercicio podría mejorar la condición física de los matalotes jorobados criados en cautiverio y así aumentar la eficacia de la reintroducción.     

High levels of gene flow in the California vole ( Microtus californicus ) are consistent across spatial scales

Gene flow links the genetic and demographic structures of species. Despite the fact that similar genetic and demographic patterns shape both local population structure and regional phylogeography, the 2 levels of population connectivity are rarely studied simultaneously. Here, we studied gene flow in the California vole ( Microtus californicus ), a small-bodied rodent with limited vagility but high local abundance. Within a 4.86-km 2 preserve in central California, genetic diversity in 6 microsatellites was high, and Bayesian methods indicated a single genetic cluster. However, individual-based genetic analysis detected a clear signal for isolation-by-distance (IBD) and fine-scale population structure. Mitochondrial cytochrome b sequencing revealed 11 unique haplotypes from the one local area where we sequenced 62 individuals. Phylogeographic analysis of these individuals combined with those sampled from the northern geographic range of the species (the range of the species spans western North America from southern Oregon to northern Mexico and is centered geographically within the state of California) again indicated a lack of structure but a signal for IBD. Patterns of gene flow thus are consistent across spatial scales: while dispersal of the California vole is limited across geographic distance, there is nonetheless considerable movement across the landscape. We conclude that in this species, high local population abundances overcome the potential genetic and demographic effects of limited dispersal.     

Roost sites used by Sandhill Crane staging along the Platte River, Nebraska

We assessed the influence of water depth, extent of unobstructed view, and human disturbance features on use of roost sites by Sandhill Cranes along the Platte River, Nebraska, during spring migratory stopover. Aerial photos taken near dawn were used to determine areas of flock use and habitat availability in four sample reaches, and measurements were made on the ground at flock roost areas. In general, depths of 1-13 cm were used by sandhill cranes in greater proportion than those available. Exposed sandbars and depths >20 cm were avoided, while depths of 14-19 cm were used in proportion to their availability. Sites 11-50 m from the nearest visual obstruction were used significantly greater than their availability, while sites 0-4 and >50 m from visual obstructions were avoided. Sandhill Cranes avoided sites near paved roads, gravel roads, single dwellings, and bridges when selecting roost sites; however, they did not appear to be disturbed by private roads, groups of residential buildings, gravel pits, railroads, or electrical transmission lines.     

Radio harness system for bobcat kittens

Eight bobcat kittens were fitted with a specially designed harness system supporting a radio transmitter. These kittens were the youngest known to be radio-instrumented. This system was used successfully through two seasons, from June 1989 to January 1991. Litters of kittens were located soon after birth for weighing, marking, and aging (by tooth eruption). During the first year when kittens were at least eight weeks old and six weeks old the second year, attempts were made to radio-instrument kittens in each litter. This harness system allowed litters to be located periodically until their death or dispersal. We were able to collect important data during the most crucial and least known weeks of the lives of bobcat kittens.     

Least Bell's Vireo breeding records in the Central Valley following decades of extirpation

The Least Bell’s Vireo ( Vireo bellii pusillus ) was listed as state endangered in 1980 and federally endangered in 1986 in response to a sharp population decline and range reduction. This vireo commonly bred in riparian forests throughout the Central Valley of California, but prior to 2005, no nesting pairs had been confirmed in the region in over 50 years. On 29 June 2005, a Least Bell’s Vireo nest was located in a 3-year-old riparian restoration site at the San Joaquin River National Wildlife Refuge in Stanislaus County, California. In 2006, a Least Bell’s Vireo pair returned to the refuge to successfully breed, followed by an unsuccessful attempt in 2007 by an unpaired female. These records are approximately 350 km from the nearest known breeding population and appear to be part of a growing number of sightings outside of the species’ current southern California breeding range. These nesting attempts lend credence to the idea that extirpated species can recolonize restored habitat by long-distance dispersal.     

Predatory bird populations in the east Mojave Desert, California

We surveyed 7 species of predatory birds weekly during a 12-month period (December 1992 through November 1993) in the east Mojave Desert, California. The Common Raven ( Corvus corax ) was the most frequently observed species with an average of 6.9 sightings per 100 km. Turkey Vultures ( Cathartes aura ), Red-tailed Hawks ( Buteo jamaicensis ), Loggerhead Shrikes ( Lanius ludovicianus ), American Kestrels ( Falco sparverius ), Golden Eagles ( Aquila chrysaetos ), and Prairie Falcons ( Falco mexicanus ) were seen in decreasing order of frequency of observation through the study period. Ravens, Red-tailed Hawks, Loggerhead Shrikes, American Kestrels, and Prairie Falcons were seen throughout the year. Turkey Vultures were not present during winter months, while Golden Eagles were seen only during November and December. Turkey Vultures, Red-tailed Hawks, and ravens were most numerous on agricultural lands, while Loggerhead Shrikes were most common at urban areas. Raven numbers increased with increasing number of linear rights-of-way parallel to the survey route. Perching was the most common behavior type, although Turkey Vultures and ravens were often observed soaring, flying, or standing on the ground near highways. Transmission powerline towers and telephone poles were used as perch sites disproportionately to availability.     

Habitat use of leatherside chub ( Gila copei ) in the presence of predatory brown trout ( Salmo trutta )

The objectives of this study were to (1) examine distribution and habitat use of leatherside chub ( Gila copei ) in a creek with high densities of predatory brown trout ( Salmo trutta ), and (2) compare study results with published accounts of leatherside chub habitat use in streams with few or no brown trout. A 14-km section of Diamond Fork Creek, Utah, was point-shocked to determine macrohabitat (main channel and lateral habitat) and microhabitat (current, depth, substrate, and cover) use of leatherside chug. At the macrohabitat level, leatherside chub were most common in lower reaches of Diamond Fork Creek where the channel was braided and lateral habitats (cutoff pools and backwaters) were abundant. Only a single leatherside chub was found in the main channel of Diamond Fork. Investigations in other systems lacking brown trout indicated that leatherside chub occupy main channel habitats. At the microhabitat level, we found significant positive associations between presence of leatherside chub and both habitat depth and silt. In addition, we found a significant negative association between presence of leatherside chub and number of brown trout. Our results suggest predation by brown trout may limit leatherside chub to lateral habitats that could provide refugia against predation. The introduction of brown trout to systems with little lateral habitat could have serious effects on persistence of resident leatherside chub populations.     

Environmental attributes correlating with density of blackbrush ( Coleogyne ramosissima ) shurbs in the Spring Mountains of southern Nevada

Discovery of distinct mid-elevational bands of blackbrush ( Coleogyne ramosissima Torr.) shrublands on desert mountain slopes in the Mojave Desert caused an investigation of the relationships between environmental factors and Coleogyne distribution. Environmental factors were quantitatively examined to determine which were significant predictors of Coleogyne density at upper-elevational limits (ecotones) in the Spring Mountains of southern Nevada. Path analysis revealed significant, direct causal effects of air temperature, soil moisture, soil depth, and percent litter cover on the distribution of Coleogyne . Specifically, air temperature was a significant positive predictor, while soil moisture, soil depth, and percent litter cover were significant negative predictors of Coleogyne density, with the effects of other environmental variables parceled out. Path analysis also indicated that indirect effects of soil pH, bulk density, compaction, percent pore space, organic matter, soil temperature, salinity, cryptogam, and percent bare soil and rock cover on Coleogyne density were substantially more potent than their direct casual effects. Environmental attributes associated with elevational changes correlate with and may determine the density of Coleogyne shrubs at upper ecotones in southern Nevada.