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1.
Observations and excavations of thatching ant nests from 1990 to 1994 at 2560 m in Colorado provided information on the numbers and behavior of males and winged and wingless queens. Nuptial activity was compared to that reported by other investigators at lower altitudes. Reproductives were observed from 24 June to 15 August. Activity was greatest in 1993 when reproductives were on 10 of 98 mounds in the area. Mating and swarming occurred on rabbitbrush 4 m from 1 nest 2-6 July. The number of wingless queens in 4 excavated nests varied from 0 to 198.  相似文献   

2.
The sagebrush biotype is the largest in the western United States. This vast sagebrush community is thought to harbor equally vast and diverse arthropod communities, but these remain little explored. Our objective was to examine the diversity, abundance, and seasonal phenology of arthropod taxa found on the dominant shrub of the sagebrush ecosystem, big sagebrush ( Artemisia tridentata ). We wanted to improve understanding of this little-studied arthropod assemblage that may play significant roles in the dynamics of sagebrush populations and the sagebrush ecosystem. We sampled free-living and gall-forming arthropods from a stratified random sample of sagebrush plants at the Barton Road Ecological Research Area, Idaho, resulting in a sample of over 8000 individuals and 232 morphospecies. Species richness and abundance declined from May to August, and abundance of most taxa similarly declined over the summer. A few taxa, including Acari (mites), were notably more abundant in August. Fluid feeders were the most diverse and abundant free-living feeding guild during all months and comprised up to 79% of morphospecies. The gall formers included 4713 individuals of 12 species of gall flies ( Rhopalomyia spp.), primarily (97%) R. ampullaria. Abundance of galls increased from small to large (presumably young to old) plants. Overall, A. tridentata was host to a high diversity of arthropods, some of which have potential to cause or mitigate significant damage to their host plant. Arthropods seem likely to have the greatest impact on sagebrush early in the growing season, when they are most diverse and abundant. Documentation of the full diversity of arthropods associated with sagebrush required samples taken throughout the growing season, but a single sample early in the growing season captured a high proportion of taxa.  相似文献   

3.
White fir ( Abies concolor ) appears to be invading vegetation dominated by big sagebrush ( Artemisia tridentata ) on the southeastern slopes of the Warner Mountains of extreme northeastern California. The time of initial tree establishment within the shrubs was determined by increment borings. Possible causes of the invasion involving specific climatic conditions, fire history, and grazing use of the area during years of the establishment were explored. Heavy grazing by domestic livestock, particularly sheep, appears responsible for altering the sagebrush - grass vegetation and allowing tree invasion.  相似文献   

4.
Artemisia tridentata/Symphoricarpos oreophilus and Symphoricarpos oreophilus/Artemisia tridentata  plant associations were studied in northeastern Nevada. A 60-stand reconnaissance followed by a detailed study of 37 stands differentiated five important habitat types using an association table approach. Data reduction with DECORANA and TWINSPAN also described five plant associations that were differentiated by species occurrence and geographical distribution. All stands were found at elevations between 2,200 and 3,100 m in areas where snow accumulates and is late to melt. Stands are found on 15 families of soils that are relatively deep, often skeletal, dark colored, and productive. The dominant perennial grasses included Agropyron spicatum, Agropyron trachycaulum, and Festuca idahoensis.  相似文献   

5.
A field study of the thatching ant, Formica obscuripes Forel, at 2560 m elevation in Colorado provided information on mound density, composition, dimensions, and temperatures; worker longevity; and mite parasitization. Density was 115 mounds/ha. Mounds had 1-52 entrances and Peromyscus fecal pellets in the thatch. Mounds conserved heat and exhibited thermal stratification. Excavations of 4 nests revealed depths of 0.3 m to almost 1 m, novel myrmecophiles, and 0-198 wingless queens per nest. Marking experiments demonstrated that some workers overwinter and live more than a year.  相似文献   

6.
Workers of Great Basin Desert thatch ants ( Formica obscuripes Forel) dig simple secondary nests at the base of plants upon which they tend aphids and scales. These secondary nests house only foragers, with the number of foragers occupying each nest positively correlated with the number of worker-tended Homoptera feeding on plant foliage above. Thatch ant secondary nests are cooler than 25 cm below the dome top of the primary nest and maintain a significantly more constant temperature than is observed on the ground surface or in the plant canopy. Thatch ant foragers use secondary nests for at least two purposes: as a cool refuge for Homoptera tenders when midday plant canopy temperatures rise during the summer months, and as the primary place within which Homoptera tenders transfer honeydew to larger "honeydew transporters" for ultimate transport back to the primary nest.  相似文献   

7.
The demography of black sagebrush ( Artemisia nova Nelson) was investigated in the Buckskin Mountains of western Nevada to determine patterns of stand renewal in sagebrush communities currently free from wildfires. Biomass sampling was conducted to develop growth classes that reflected apparent age of the shrubs. The density of black sagebrush plants was twice that of basin big sagebrush ( A. tridentata ssp. tridentata Nutt.) in adjacent communities on contrasting soils (2.2 versus 1.1 plants per m 2 ). Black sagebrush accumulated only 75% as much woody biomass as big sagebrush. Regression equations were developed and tested for predicting total woody biomass, current annual growth (CAG), and leaf weight of black sagebrush plants. Apparent age classes were developed both for the black sagebrush plants and the sub-canopy mounds on which they grew. Discriminant analysis was used to test this classification system. Plant succession, apparently controlled by nitrate content of the surface soil, appeared to eliminate the successful establishment of black sagebrush seedlings on the mounds. After the shrubs die, the mounds eventually deflate. We propose that mounds reform around shrub seedlings, but because seedling establishment is so rare in these communities, this could not be verified.  相似文献   

8.
9.
《Journal of Natural History》2012,46(12):1461-1487
The araneofauna of the extreme Southern Hemisphere is highly impoverished and disharmonic. Four dead anthropogenic immigrant spiders have been collected from Antarctica while only 115 verified species from 26 families are reported on the islands of the Southern Ocean. Cluster analysis of the verified Southern Ocean species distribution data identifies a weak, but distinct, Neotropical/South Atlantic association together with robust South Indian and South Pacific biogeographic clusters. These groupings, largely attributed to vicariance and/or endemism, contain little evidence of post-Pleistocene dispersal. Indeed the 14 records of anthropogenic origin suggest that the pace of recent human-mediated introduction has been at least 30 times more rapid than that of Holocene natural dispersal.  相似文献   

10.
Three characteristics of the silk devices of 12 species of Salticidae and three species of spiders from conventional web-building families (Dipluridae, Eresidae and Stiphidiidae) were investigated: macrostructure; prey-holding ability (measured by escape time for five types of insects); and the structure of the silk itself, as revealed by SEM. Five types of salticid nests were recognized, and a few salticids build webs. The webs of the eresid Stegodyphus mimosarum consist of thick structural threads and fine cribellate fibres. Disparity of thread diameter, although not as extreme, was observed in the webs and nests of the other species. In the webs and nests of all species, there were threads that merely rode one over the other without forming junctions and secure ‘naked’ junctions lacking accessory fibres and ‘sleeves’. Ensheathed junctions, which had ‘sleeves’, were found only in webs of Portia (Salticidae) and Cambridgea antipodiana (Amaurobiidae). The cribellate webs of Stegodyphus mimosarum (Eresidae) had greater prey-holding ability than any other webs or nests tested, but all webs and nests were capable of detaining insects at least briefly. The distinctions between spider webs and nests and between sticky and non-sticky webs are discussed.  相似文献   

11.
I measured songbird abundance and vegetation cover in and around a 420-ha prescribed burn in a mountain big sagebrush community located at 2133 m elevation. Data were collected during the 3rd growing season after the fire. Brewer's Sparrow and Sage Thrasher occurred in lower abundance on sites that were largely or completely burned relative to sites that were outside the fire perimeter or within unburned islands of shrubs. The number of Brewer's Sparrow detections was linearly related to remaining sagebrush cover. In contrast, Horned Lark occurred at higher abundances on sites where shrub cover had been removed in the prescribed burn. Cover of perennial grasses and cover of 4 of the 5 most common forbs was greater on burned sites than on unburned sites.  相似文献   

12.
Winter crude protein content, in vitro digestibility, and productivity were determined for seven accessions of black sagebrush ( Artemisia nova ) grown in a uniform garden. No significant differences were detected among the accessions for any of these attributes. Mean crude protein was 6.8% of dry matter. Accessional range was from 5.8% to 7.3%. Mean in vitro digestion was 54.8% of dry matter; accessional range, 51.9% to 57.2%. Mean current year's growth (a measurement of productivity) was 4.3 cm; accessional range, from 3.7 to 5.1 cm. In comparison to other winter forages, black sagebrush ranks high for winter levels of crude protein and very high in winter digestible dry matter but low in productivity.  相似文献   

13.
《Journal of Natural History》2012,46(25-28):1659-1678
Jumping spiders (Salticidae) are known for their elaborate vision‐based display behaviour, and a sizeable minority of the species in this large family resemble ants. The display repertoire of two ant‐like salticid species from the Philippines is investigated. Myrmarachne assimilis is a specialist ant mimic, closely matching the appearance of the weaver ant Oecophylla smaragdina. Myrmarachne bakeri is a generalist mimic, which, although ant‐like, is not a close match to any sympatric ant species. Myrmarachne are sexually dimorphic, with males having enlarged chelicerae. The copulatory posture of Myrmarachne is unique among salticids, apparently as an adjustment for the male's elongated chelicerae. Details concerning the intraspecific behaviour of Myrmarachne appear to be adjustments to living in environments populated by numerous other animals with similar appearance (ants). However, the specialist and the generalist that were investigated have display repertoires that are broadly similar to each other and to those of more typical salticids. Generally, the display behaviour of Myrmarachne appears not to have necessitated dramatic deviation from typical salticid display and mating strategies.  相似文献   

14.
《Journal of Natural History》2012,46(6):1287-1295
A new species of Achaearanea (Theridiidae) is described from the Cedarberg in South Africa. Its unusual morphological features include the position of the spinnerets directly behind the epigastric fold. The male palp is a modification of the palpal conformation of other Achaearanea. This spider lives in a spherical retreat comprizing silk, sand and pebbles. This structure typically dangles from only one thread and has a tiny opening at the bottom that leads into a spirally-coiled tunnel. Males and females build spirals in opposite directions. This enables the male to construct his retreat against that of the female in such a way as to form a brood chamber. Retreats are situated in cool places under low overhanging rocks or branches. The configuration of the narrow, suspended retreat may decrease the spider's vulnerability to enemies while foraging for ants in a typical theridiid fashion.  相似文献   

15.
Like many seed-harvesting ants, the western harvester ant ( Pogonomyrmex occidentalis ) can act as both a predator and a seed disperser. Dispersal results when seeds are dropped en route to the nest, are left in nest granaries when colonies die or are abandoned, or are removed from granaries and discarded in nest middens. This study examined the density and species identity of seeds discarded in harvester ant nest middens and compared them with those found in nearby soils. Nineteen species of seeds were recovered from middens, compared with 13 species in 5-m reference areas and 9 species in adjacent disk areas. Total density of sound seeds was nearly 3 times higher in middens than at 5 m from the nest and nearly 50 times higher than in disk soils. Moreover, 4 of the 6 most common species overall were significantly more abundant in middens. One species, Munro globemallow ( Sphaeralcea munroana ), was recovered from nearly 50% of middens but was not found in the other 2 areas. These findings suggest that the western harvester ant is a potentially important disperser of some sagebrush-steppe plant species.  相似文献   

16.
Antelope bitterbrush ( Purshia tridentata ) is a preferred browse species that is susceptible to decreases in population density due to fire. The reduction in density of this species due to fire was determined by sampling areas within and adjacent to the burn. The 1975 burn caused a significant reduction in the population density of bitterbrush. It was also determined that rate of growth was lower for plants within the burn.  相似文献   

17.
The effects of elk ( Cervus elaphus ), pronghorn ( Antilocapra americana ), and mule deer ( Odocoileus hemionus ) browsing on shrubs in big sagebrush ( Artemisia tridentata ) communities were monitored over a 31-year period in Yellowstone National Park. Ungulates were restricting Wyoming big sagebrush (spp. wyomingensis ) heights, size, and recruitment on the lower-elevation stratum only, while no such suppression was observed on the high-elevation stratum. Parallel increases in mountain big sagebrush (spp. vaseyana ) densities and cover occurred over the study period on both browsed and unbrowsed sites at the higher-elevation stratum, although big sagebrush, green rabbitbrush ( Chrysothamnus viscidiflorus ), and horsebrush ( Tetradymia canescens ) were slightly taller and crown sizes were slightly larger on unbrowsed than browsed sites. Wyoming big sagebrush utilization (percent leader use) was eight times higher ( ̄ x = 87 ± 7.2% by pronghorns, mule deer, and elk) on the low-elevation winter ranges stratum (the Boundary Line Area [BLA] portion of the winter range), while mostly mountain big sagebrush with leader use averaged only 11 ± 4.1% (nearly all by elk) on the high-elevation range stratum. In addition, annual aboveground biomass production of big sagebrush did not differ between browsed and unbrowsed study sites on the high-elevation stratum of the winter range. Population turnover was higher on browsed plots versus unbrowsed plots. No difference was observed in percent dieback of big sagebrush adult plants between browsed and unbrowsed plots at the higher stratum. Browsing did not influence the number of leaves or seedstalks per plant ( P > .05), but leaves averaged 45% longer and seedstalks 42% longer on browsed big sagebrush. Ungulate browsing, however, apparently suppressed production, germination, and survival of Wyoming big sagebrush on the low-elevation stratum. Numbers of Wyoming big sagebrush declined 43% and cover declined 29%, 1957-1990, on browsed sites on the BLA. Annual biomass production on browsed sites at the low-elevation stratum was only 6-35% that of unbrowsed sites, and big sagebrush recruitment was less on browsed sites. Percent leader use of big sagebrush did not differ between the period of ungulate reductions, 1962-1969, and the 1980s on the lower stratum ( ̄ x = 87% leader use), but utilization was less on higher portions of the winter range during the period of elk reductions ( ̄ x = 2%) than during the 1980s following cessation of elk controls ( ̄ x = 11%).  相似文献   

18.
19.
Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* 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-priority:99; mso-style-qformat: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:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Burrows of the sagebrush vole ( Lemmiscus curtatus ) were analyzed by injecting them with expanding polyurethane foam. Average mean depth ± 1 SE of four burrows was 12.5 ± 2.6 cm. Tunnels were wider than high and flat on the bottom. Three of four burrows were nearly linear, with an average of five entrances. Burrows usually contained one nest made of Artemisia tridentata bark. No middens or communal nests were found. The burrow structure in sagebrush habitat suggests that sagebrush voles occur singly or in pairs rather than in colonies.  相似文献   

20.
《Journal of Natural History》2012,46(47-48):2873-2915
Southwest China is one of three famous karst areas of the world but research on cave spiders of the area is sparse. A Chinese endemic midget spider genus and species, Qianleptoneta quinquespinata (Leptonetidae) was erected by Chen and Zhu, 2008 Chen, HM and Zhu, MS. 2008. One new genus and species of troglobite spiders (Araneae, Leptonetidae) from Guizhou, China. J Dali Univ., 7(12): 1114.  [Google Scholar]. Here, based on numerous materials collected from Guizhou Province, the mainly karst area of southwest China, Qianleptoneta is revised. Ten new species are described and illustrated: Q. triangula, Q. nuda, Q. identica, Q. lycotropa, Q. multiseta, Q. lophacantha, Q. robustispina, Q. palmata, Q. sublunata and Q. megaloda. The natural history of each species is presented.  相似文献   

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