Plant species richness, diversity, and frequency were quantitatively examined within Pogonomyrmex rugosus (seed-harvester ant) nest discs and at various distances from nest discs in a Larrea tridentata-Ambrosia dumosa (creosote bush-white bursage) shrubland in southern Nevada. Woody vegetation at and near the edge (perimeter) of nest discs showed decreased species richness, density, and frequency compared with vegetation in adjacent reference areas (nonnest; 4 m beyond discs). Four of 17 species were found with significantly lower density and frequency on nest discs than at greater distances from the nest. Thirteen of 17 species were not found on nest discs at all. Species richness, density, and frequency were significantly and negatively correlated with distance from nests. Woody vegetation was sparse and less variable in composition when occurring at discs and edges of discs. Local disturbance caused by P. rugosus nests may largely alter immediate surrounding vegetation in the L. tridentata-A. dumosa shrub land of southern Nevada.
Forty-two white-tailed deer fawns ( Odocuileus virginianus dakotensis ) were captured and fitted with radio transmitters and observed from June through September 1991 and 1992 to determine diurnal bed site use in the Black Hills of South Dakota. Fawns were monitored biweekly during daylight hours and 259 bed sites were located. In addition, 301 random sites were measured for comparison. Of 31 habitat variables measured, 8 were significant to determine use by fawns for a bed site when compared with random sites. Sites used by fawns were in relatively open stands of ponderosa pine ( Pinus ponderosa ) with mean basal area of approximately 11 m 2 /ha compared to 16 m 2 /ha in random sites. Fawn bed sites had greater mean vegetation cover, which ranged from 28.1% to 36.0%, compared with 19.9% and 33.8% at random sites in 1991 and 1992, respectively. Mean vegetation height was 101 cm at bed sites compared to 75 cm at random sites. Current timber harvest standards for stocking levels of pine range from 14 m 2 /ha to 18 2 /ha in the Black Hills, which are similar to our random sites. These levels preclude adequate development of understory characteristics used by white-tailed deer fawns for bed sites.
Ecology of the endangered Gila topminnow is reviewed, described, and reconstructed; natural conditions are placed in perspective with human-altered habitats of today. In the natural state of waxing and waning of habitat size as a function of precipitation patterns and, catastrophic events such as severe winter cold, the species in the past likely underwent dramatic expansions and contractions in population size and geographic range. Today, population expansions are unlikely because of constraints imposed by human activities. The original patterns of dispersal from refugia in "good" times and retreat in "bad" times, if they are to occur, must be re-created through human translocation. Further, most refugia now are destroyed. or inaccessible to recolonization, so remnant, natural populations, along with established, transplanted stocks of appropriate size and genetic quality need protection. Populations also must he established and maintained in artificial refugia. Last, even if connectedness were to Le reestablished and refugia provided, intervening habitats harbor introduced piscivores such as western mosquitofish that: interdict and eat dispersing topminnows and their progeny. Elimination, exclusion, or management against such offending species is mandatory to prevent topminnow extinction and achieve recovery.
A total Of 33 species of blow flies (Diptera: Calliphoridae) are recorded from Idaho, They include 1 species each of Cochliomyia, Phormia, Protophormia, Trypocalliphora, Cyanus, Cynomya, and Melanodexia; 12 species of Protocalliphora; 5 species of Lucilia; 6 species of Calliphora; and 3 species of Pollenia. Other calliphorid species that may also occur in the stare include 5 species of Protocalliphora and 3 species of Calliphora. Known distribution, periods of activity, abundance within the state, and biological notes are provided.
The purpose of this study was to observe the dynamics of a meta-population of Mimulus guttatus. Changes in size and location of 16 original populations and the new populations established in their vicinities in Big Cottonwood Canyon, Salt Lake county, Utah, were observed for 25 yr. Twenty-three new populations appeared. Seven original populations and 13 new populations had become extinct by the end of the observation period in 1996. Many populations died out and were reestablished, often repeatedly, during the observation period. Altogether there were 54 population disappearances and 34 reappearances. Many populations changed size as much as 100-fold or more from year to year. There were spectacular examples of populations expanding to fill newly available, large habitats. Frequent extinctions were due overwhelmingly to the canyon drying trend, which led to the drying up of most Mill D North drainage springs, creeks, and ponds. Precipitation and minimum temperatures increased moderately during the observation period. The growing season lengthened almost 50%, a typical consequence of global warming. The drying trend, lengthened growing season, and disappearance of Mimulus populations in Big Cottonwood Canyon appear to be a clear, local example of global warming.
The Ferruginous Hawk, a breeding bird endemic to North America, was named Falco ferrugineus in 1838 by H. Lichtenstein, curator of the Berlin Zoological Museum. The type was collected by F. Deppe near present day Monterey, California. In 1844 G.R. Gray of the British Museum assigned the Buteo regalis to a Ferruginous Hawk specimen of unknown origin, but perhaps donated to the museum by John Phillips, a renowned British geologist. The species was known as Falco (Buteo) ferrugineus until the 1920s when it was discovered that this epithet was occupied. The next name in priority was Gray's Buteo regalis , which then became valid. The species has been known by a number of common names. Even though any reference to the rusty brown markings on the otherwise white plumage is no longer part of the species specific name, the Ferruginous Hawk continues to be the most frequently used common name.
Before 1990 the spotted bat (Enderma maculatum) was known in Wyoming from only 2 records. Between June 1994 and May 1997 we documented habitat use and observations incidental to conducting a bat inventory of caves and abandoned mines. By monitoring audible echolocation calls, we observed bats at mist-netting sites. Spotted bats were heard or captured on 13 nights at 10 locations, all of which were near canyons or high cliff faces. No foraging habitat preferences were noted. E. maculatum occurrence appears to be related to roost structure, roost availability, and proximity to a permanent water source.
Triglochin maritima L. (arrow grass), an herbaceous perennial in the family Juncaginaceae, is widely distributed in inland and coastal salt marshes of North America Triglochin maritima seeds from a population growing in a salt marsh at Faust, Utah, were germinated at 4 temperature regimes (12-h night/12-h day, 5-15 degrees C, 5-25 degrees C, 10-20 degrees C, and 15-25 degrees C) and 5 salinities (0, 100, 200, 300, 400, and 500 mol m(-3) NaCl) to determine optimal conditions for germination and level of salt tolerance. Ungerminated seeds were returned to distilled water after 20 d to determine whether seeds could recover from salinity treatments. Maximum germination occurred in distilled water and increases in NaCl concentration progressively inhibited seed germination. No seeds germinated at concentrations higher than 400 mol m(-3) NaCl. A temperature regime of low night (5 degrees C) and high day (25 degrees C) temperature yielded maximum germination; all other temperature regimes significantly inhibited seed germination relative to this optimum. Recovery of germination was highest at 5-25 degrees C and lowest at 5-15 degrees C. Recovery of seed germination when seeds were transferred to distilled water from salt solutions was highest at 5-25 degrees C (72%) for seeds exposed to the 500 mol m(-3) NaCl pretreatment and significantly reduced at other temperature regimes. The recovery germination response indicates a synergistic inhibitory interaction effect on germination when seeds were exposed to high salinities at suboptimal thermoperiods.
During July to September 1994-1995, I examined water temperatures at the lower end of the elevational distribution of redband trout ( Oncorhynchus mykiss gairdneri ) in 4 streams in the Owyhee Mountains in southwestern Idaho. Maximum water temperatures in Castle, Shoofly, Little Jacks, and Big Jacks creeks during low flows during a drought in 1994 ranged from 26.7° C to 29.0° C. Water temperatures fluctuated 9.5-11° C during the 24-h period maximum temperatures were observed. Stream flows at the lower end of Big Jacks and Little Jacks creeks in 1994 were 3 s -1 and subsided underground 50-130 m downstream pools inhabited by trout. Trout were distributed to lower elevations where drainage basin area was larger in 2 of 3 yr ( P 5 km downstream of the lowest pool inhabited by trout in 1995-1996.
Sarcobatus Nees., a genus of North American halophytic shrubs, consists of 2 species: S. vermiculatus (Hook.) Torr. (n = 18, 36), which is widespread in western North America, and S. baileyi Cov. (n = 54), endemic to Nevada. Within S. vermiculatus, populations of n = 36 are widely distributed, whereas populations of n = 18 are found only in the Sonoran Desert, northern California, and northwestern Great Plains, locations at the periphery of the species range. Although the chromosome number of n = 18 is apparently tetraploid, failure to form an n = 27 race intermediate to those of n = 18 and n = 36 suggests that n = 18 S. vermiculatus is of significant age and that it behaves chromosomally as a diploid. Sarcobatus has a long fossil pollen record and endured Pleistocene climatic extremes with little range displacement.
Plant species richness, density, and frequency were quantitatively examined within Pogonomyrmex rugosus (seed-harvester ant) nest discs and at various distances from nest discs in a Larrea tridentata-Ambrosia dumosa (creosote bush-white bursage) shrubland in southern Nevada. Woody vegetation at and near the edge (perimeter) of nest discs showed decreased species richness, density and frequency compared with vegetation in adjacent reference areas (nonnest; 4 m beyond discs). Four of 17 species were found with significantly lower density and frequency on nest discs than at greater distances from the nest. Thirteen of 17 species were not found on nest discs at all. Species richness, density, and frequency were significantly and negatively correlated with distance from nests. Woody vegetation was sparse and less variable in composition when occurring at discs and edges of discs. Local disturbances caused by P. rugosus nests may largely alter immediate surrounding vegetation in the L. tridentata-A. dumosa shrubland of southern Nevada.
Soldier beetles of 2 species, Chauliognathus basalis and C. deceptus, were examined to test the Crespi hypothesis that positive assortative mating by size is caused by mate choice. Specifically, we tested the prediction that if mate choice involves choosing the largest mate available, then mating individuals will be larger than nonmating individuals. Four samples were taken, at different times during the mating season, from each of 2 sites. Each sample consisted of mating pairs, nonmating males, and nonmating females. Some of the samples contained beetles of both species; others contained beetles of a single species. For each gender elytron lengths of mating individuals were compared with elytron lengths of nonmating individuals. We found no effect of mating status (mating vs, nonmating) on elytron lengths in samples that exhibited assortative mating (which occurs where 2 species coexist). Surprisingly we found a consistent effect of mating status on elytron lengths in samples that did not exhibit assortative mating (which occurs where only 1 species exists). Our results do not support the mate-choice hypothesis. Instead, mate choice and assortative mating appear to be alternative mating patterns in which mate choice occurs where a single species exists and assortative mating occurs where 2 species coexist.
The Black Hills of South Dakota and Wyoming are an insular mountain range completely surrounded by the Great Plains. The stonefly (Plecoptera) fauna of the Black Hills was surveyed and zoogeographic affinities examined. Twenty-seven species representing 22 genera and 6 families were found. Fifteen new state records for South Dakota and 2 for Wyoming are presented. Two species are removed from the South Dakota list. An analysis of the North American distribution of each species showed a strong relationship between the Black Hills and the Rocky Mountains, with much weaker relationships between the Black Hills and eastern and northern regions. Results of a logistic regression analysis comparing factors contributing to long-distance dispersal ability against presence/absence in the Black Hills were inconclusive. However, other evidence suggests that the Black Hills fauna is a result of expansion and subsequent vicariance of stonefly populations during Pleistocene climatic oscillations.
Maximizing desired plant diversity has been suggested as a means of minimizing non-indigenous plant invasion on rangeland by maximizing niche occupation. Competition between 2 desired indigenous species, Pseudoroegneria spicata (Pursh). Love (bluebunch wheatgrass) and Hedysarum boreale Nutt. var. boreale (northern sweetvetch), and a non-indigenous invader, Centaurea maculosa Lam. (spotted knapweed), was quantified using growth of isolated individuals and 2 three-species addition series experiments. Seeding densities of P. spicata remained constant at 0, 200, 400, and 800 seeds m -2 in both experiments. H. boreale and C. maculosa seeding densities were 0, 200, 400, and 800 seeds m -2 , respectively, in the 1st experiment and 0, 400, 800, and 1600 seeds m -2 , respectively, in the 2nd experiment. Densities were factorially arranged. Pots were place in an environmental chamber (12 C, 12-h day length, 200 µmol photons m -2 s -1 spectral light) in a randomized-complete-block design. After 90 d the growth rate of P. spicata (92.1 mg d -1 shoot growth) was greater than that of the 2 forbs (1.6 and 5.5 mg d -1 for H. boreale and C. maculosa , respectively), and growth rates of the 2 forbs were similar to one another. Curvilinear regression indicated that intraspecific competition was more important in determining shoot weight than intraspecific competition. In addition, the 2 forbs competed more directly with each other than with P. spicata . Competition coefficient ratios (1.42 and 1.53 for P. spicata with H. boreale and C. maculosa , respectively, and 1.03 for H. boreale with C. maculosa ) indicated substantial partitioning of resources between P. spicata and each of the forbs. Little or no resource partitioning occurred between forbs. This study suggests that increasing desired plant diversity may minimize weed invasion by increasing niche occupation.
