Computer analysis of cross sections of leaves of Chrysothamnus taxa and their relation to environmental conditions

Thirty-eight accessions of 20 taxa (species and subspecies) of Chrysothamnus from a range of environments were grown in a uniform garden. During mid-June, terminal and lateral leaves were removed, fixed, and processed for light-microscopy studies. Area and perimeter measurements of ink tracings of midleaf vein cross sections were measured using computer-scan techniques. Leaf area and perimeter were compared with vein perimeter and area measurements. Area and perimeter of these Chrysothamnus leaves varied in response to the environment at the collection location. Plants native to hot, dry conditions had small, thick leaves, whereas plants native to cooler, more mesic conditions had relatively large, thin leaves. Similarly, leaves with round veins were adapted to hot, dry environments and leaves with elliptical veins were adapted to cooler, more mesic environments. Both terminal (young) and lateral (older) leaves were sampled. Terminal leaves showed significant (p < .05) correlational responses to environmental parameters, whereas the lateral leaves, while fronding in the predicted morphological directions, did not generally show significant responses. The different responses of terminal and lateral leaves may have been due to canopy position and uniform environmental conditions of the garden. Leaves with large cross sections characteristically had large veins, and leaves with small cross sections characteristically had small veins. Large leaf cross sections were normally flat. Small leaf cross sections were normally round. Decreasing leaf size and increasing leaf thickness were correlated with aridity.     

Soil water and temperature response to prescribed burning

Normal 0 false false false EN-US X-NONE X-NONE 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-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;} Prescribed burning of Texas wintergrass ( Stipa leucotricha Trin. & Rupr.) communities reduced soil water contents for two to six months, and additional reductions occurred when the subsequent crop of cool-season grasses and forbs began growth. These soil water reductions occurred despite reduced plant production following burning. Soil water reductions were greater at 15 to 45 cm depths than in the upper 15 cm and greater following spring burning. Soil temperatures were higher on burned plots for most of the first year following burning. &nbsp;&nbsp;     

Development and longevity of ephemeral and perennial leaves on Artemisia tridentata Nutt. ssp. wyomingensis

Big sagebrush ( Artemisia tridentata Nutt.) is one of the most successful plants in the Great Basin based on its abundance and wide distribution. The development of dimorphic leaves may be an important mechanism attributing to its adaptive and competitive abilities. Development, persistence, and proportions of ephemeral and perennial leaves on Wyoming big sagebrush ( Artemisia tridentata Nutt. ssp. wyomingensis ) were studied for two years. The large ephemeral leaves are the first to develop in early spring. As early developing ephemerals mature and stems elongate, new ephemeral and perennial leaves develop in the axes of these large ephemerals. Perennial leaves expanded in the summer of their first growing season, persisting on the shrub until their abscission during summer drought of the second growing season. Plants maintained 33% of their leaf weight through the winters of 1985 and 1986. Active leaf and stem growth occurred at soil water potentials above &ndash;0.2 MPa.     

Identification of Purshia subintegra (Rosaceae)

Populations of Purshia in central Arizona are intermediate in some characters between Purshia subintegra , an endangered species, and Purshia stansburiana , the common cliffrose. These intermediates may represent forms derived from a history of hybridization and introgression between putative parent species. Morphological data were obtained from 216 pressed speciments of P. subintegra , P. stansburiana , and introgressed forms. Over 50 separate discriminant function analyses (DFA) and principal components analyses (PCA) were run on numerous combinations of raw and log-transformed data. The best variable suite, providing the clearest discrimination between groups, used log-transformed data on 15 morphological characters, but DFA post-hoc identifications were 90-100% correct with only 7 characters using raw data. DFA distinguished four separate nodes of variation. Two groups consisting of 122 P. subintegra and 29 P. stansburiana were easily discriminated in DFA and were distinguished in PCA as well. Introgressed forms were consistently identified in two much less well-defined groups of 46 and 19 specimens. Introgressed forms are not intermediate between the two supposed parents in some characters, appearing most similar to P. stansburiana in most measured characteristics. Principal distinguishing characteristics of the four groups are as follows: P. subintegra -usually eglandular, has 0-2 leaf lobes and short hypanthia-pedicels; P. stansburiana -always abundantly glandular, has 4 leaf lobes and short hypanthia-pedicels; the introgressed from ""Tonto"" is usually eglanduluar, has 4 leaf lobes and long hypanthia-pedicels; the introgressed form ""Verde"" is usually glandular, has 4 leaf lobes and slightly shorter hypanthia-pedicels.     

Winter stomach contents of South Dakota badgers

Normal 0 false false false EN-US X-NONE X-NONE 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-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;} Stomach contents of 33 hunter and trapper killed badgers, Taxidea taxus, from northeastern South Dakota were examined during the 1980&ndash;81 fur season. Mammal prey species made up the bulk of the ingested food, followed by plant materials. Approximately 40 percent of stomach contents were mammals, 35 percent were of plant origin, 10 percent were birds, 10 percent were insects, while the remainder was mostly inorganic materials. Little significant difference was found in variety of food items consumed by each sex. South Dakota badgers are opportunistic foragers in the wintertime when food is scarce. Individual food items are usually taken in quantity when encountered by badgers.     

Experimental manipulations of precipitation seasonality: effects on oak ( Quercus ) seedling demography and physiology

Predicted changes in regional precipitation patterns and soil moisture caused by anthropogenic trace gas emissions may affect the distribution and abundance of woody plants in arid and semiarid regions. To test the response of woody plants to potential changes in precipitation regimes, we manipulated summer and winter precipitation on plots that contained seedlings of Quercus emoryi Torr. (Emory oak), the dominant tree in oak savannas of the southwestern United States. Throughout the growing season, we monitored seedling survival and physiology (predawn leaf water potential, midday instantaneous gas exchange, and leaf carbon isotope discrimination). Seedling survival and physiological performance differed little between treatments, which embodied 50% changes to quantities of summer and winter precipitation, and encompassed a continuum of precipitation from 359 mm · year -1 to 846 mm · year -1 . However, survival and physiological performance of seedlings were negatively impacted by seasonal environmental conditions common to all treatments, especially during the annual pre-'monsoon' drought. Seedling predawn leaf water potentials, net CO 2 assimilation, and stomatal conductance indicate that growing conditions for Q. emoryi seedlings at this site are generally restricted to periods with adequate soil moisture (i.e., April and August). Results contrast with an assumption implicit to the ""two-layer"" soil water resource partitioning hypothesis that woody plants in all life history stages are more dependent upon winter than summer precipitation. In fact, summer precipitation appears more important than winter precipitation for Q. emoryi seedling recruitment and growth.     

The life cycle of Hydroperla crosbyi (Plecoptera: Perlodidae)

Normal 0 false false false EN-US X-NONE X-NONE 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-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;} Hydroperla crosbyi in Texas exhibited a univoltine, fast life cycle over the three - year study period. Adults emerged in February &ndash; March when mean daily stream temperature reached ca. 15 C. Reared females in the lab deposited up to three egg masses. Mean fecundity of dissected females was 787 eggs/female. Oviposition in the field was observed and described. Eggs were triangular in cross section, brown, and measured 400 &micro; m &times; 535 &micro; m. They underwent an ca. seven-month diapause until mean daily stream temperature decreased to 18 C. Eyespots appeared, and hatching followed in two to three weeks. First instar nymphs were measured and described. Male and female nymphs underwent 12 and 14 instars, respectively, and could be sexed by the sixth. Fast growth occurred in the coldest season and Simuliidae and Chironomidae larvae were preferred food throughout development. Eggs contained a mean of 6.21 cal/mg. Ash - free mean caloric value of last instar nymphs was 6.0 cal/mg. Adult males and females lost 33.8 percent and 57.6 percent, respectively, of their caloric pool through their ca. 12 days of life. &nbsp;&nbsp;     

Notes on reproduction of the side-blotched lizard Uta stansburiana stansburiana in southwest Idaho

Normal 0 false false false EN-US X-NONE X-NONE 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-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;} In 1968 and 1973 in southwestern Idaho, 275 Uta stansburiana were collected. Uta occupies low hills with rocky outcrops and flat sparse vegetation consisting of the following shrubs: Artemisia tridentata, Grayia spinosa, Atriplex confertifolia, Chrysothamnus nauseosus, and Atriplex canescens. Emergence from hibernation occurs from mid-March to early April and the first yolked follicles appear in early April, with oviducal eggs present in late April. Testicular cycle begins with the emergence of males, and spermatozoa are produced from April through July. Uta reaches sexual maturity in one year at a SVL of 40.0 mm in males and 43 mm in females. Overall clutch size is 3.75 eggs (1&ndash;2 clutches per year). Fat body size at emergence is not known, but what is present shows a decline in males and females until July, when a substantial increase occurs. Sex ratios are about 1:1 in all months and seasons except June 1968, according to chi-square analysis. &nbsp;     

Pronghorn responses to hunting coyotes

Normal 0 false false false EN-US X-NONE X-NONE 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-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;} Six accounts of pronghorn antelope ( Antilocapra americana ) chasing or attacking coyotes ( Canis latrans ) are described: three chases by individual pronghorn does, two by herds of antelope, and one joint effort by a pronghorn doe and a Short-eared Owl ( Asio flammeus ). Modifications of Berger's (1979) ungulate antipredatory defense model are proposed. &nbsp;     

Natural history of the terrestrial amphipod Cerrorchestia hyloraina Lindeman (Crustacea: Amphipoda; Talitridae) in a Costa Rican cloud forest

The field biology of the Costa Rican landhopper (Crustacea: Amphipoda: Talitridae) Cerrorchestia hyloraina Lindeman was investigated in the Monteverde Cloud Forest Reserve, Costa Rica. On the Pacific (leeward) side of the continental divide, local distribution follows a gradient of moisture, from densities of over 200 m^-2 in the elfin forest at 1600 m, to extremely low densities in drier forest types. Below 1400 m, the leaf litter is apparently too dry to support landhopper populations. On the Caribbean (windward) side of the continental divide, landhoppers occur well below 1400 m. A discussion of geographic distribution is included. Landhoppers prefer aged (microfaunally pre-processed) leaves as food, and move about only at night or in the mornings of heavily overcast days. Average female fecundity is seven eggs, with progressive loss of marsupium contents over time. The sex ratio is biased towards females. In cloud forest, breeding apparently is continuous throughout the year, with some increase after the beginning of the rainy season. There are 9–10 juvenile instars and 5–6 adult instars. The relationship of antennal segment number to total body length is linear.     

Observations on alpine vegetation near Schoolroom Glacier, Teton Range, Wyoming

Normal 0 false false false EN-US X-NONE X-NONE 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-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;} Quadrat and propagule trapping studies were made on the moraine of the Schoolroom Glacier and in adjacent dry alpine meadow vegetation in the Teton Range in 1978&ndash;1979. Forty-six species of vascular plants were collected. Distributionally, three groups of species exist. One of these is concentrated primarily on the moraine, a second in the meadow, and the third in a narrow ecotonal band at the base of the distal slope of the moraine. The moraine slopes are steep and unstable, with vegetation cover ranging from 1 to 9 percent, dominated by Cirsium tweedyi (Rydb.) Petr. Along the more stable moraine crest the vegetation cover is heavier, and is similar to that in the meadow. The meadow vegetation cover is about 50 percent, dominated by Astragalus kentrophyta Gray. Using a combination of cover and frequency as a measure of importance, dominance-diversity curves were constructed for the moraine and meadow. Both approach geometric series, which are suggested as indicating harsh environments. Abiotically pollinated species are more successful on the moraine than biotically pollinated species, but the reverse is true for the meadow. Propagule trapping studies suggest that dispersal of anemochorous propagules onto the moraine is very low compared with dispersal in the meadow.     

Comparative life history and floral characteristics of desert and mountain floras in Utah

Normal 0 false false false EN-US X-NONE X-NONE 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-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;} Life forms and floral characteristics of plants at Arches National Park (desert communities), the Mt. Nebo complex, and a subalpine meadow in the Uinta Mountains (montane and subalpine communities) were compared. Characteristics observed were (1) life form, (2) longevity, (3) pollination system, (4) flower structure, (5) flower symmetry, and (6) flower color. Common families in each flora were also compared. Results showed that there is a significant overrepresentation of shrub species at Arches, and an underrepresentation of perennial forbs. Relative number of perennial forb species was significantly higher at Mt. Nebo and the subalpine meadow than at Arches National Park. Native annuals and wind-pollinated species were significantly overrepresented at Arches. Flowers with open structure that permit free access of most insects to nectar and pollen were overrepresented at Mt. Nebo and in the subalpine meadow. The distribution of flower colors also differs significantly among these ecologically contrasting floras, with yellow being best represented in the desert and white in the mountains. &nbsp;     

Natural and unnatural; wild and cultural

Yellowstone National Parks mission and policy can be clarified by analysis of the natural and the unnatural. Nature is a comprehensive word, in some uses excluding nothing; more useful is a contrast distinguishing nature and culture . Specifying ""wild nature"" denotes spontaneous nature absent human influence. Critics claim that the meaning of wild nature, especially of wilderness, is a foil of culture. Pristine nature, often romanticized, is contrasted with a technological and industrial culture. By this account, wilderness is a social construction. Nevertheless, wild nature successfully denotes, outside culture, an evolutionary and ecological natural history, which remains present on the Yellowstone landscape, jeopardized by numerous human influences, including the invasions of exotic species. Natural processes have returned in the past, as when Native Americans left the landscape. Natural processes can be preserved today, because of, rather than in spite of, park management. Over much of the North American landscape nature is managed and at an end. Yellowstone provides an opportunity to encounter and to conserve ""untrammeled"" nature as an end in itself, past, present, and future.     

Effects of grass bug feeding and drought stress on selected lines of crested wheatgrass

The sequential effects of feeding by grass bugs ( Irbisia pacifica [Hemiptera: Miridae]) and of drought stress on the growth of 2 crested wheatgrasses (the hybrid Agropyron cristatum × desertorum and A. cristatum cv. 'Fairway') were investigated in a controlled greenhouse experiment. Growth rates of genotypes that were previously selected for resistance to grass bug feeding were not consistently greater than those of unselected genotypes when plants were exposed to bug feeding. Thus, the mechanism of resistance to bug feeding for the selected genotypes does not appear to be ""tolerance,"" i.e., rapid growth rates that allow the resistant genotypes to compensate for damage to green leaves caused by bug feeding. In addition, previous bug feeding did not exacerbate the effects of drought stress on plant growth rates; droughted plants generally had lower growth rates, independent of the presence or absence of prior bug feeding. Thus, we suspect that the selection process may have inadvertently favored green, robust plants rather than true resistance to bug feeding.     

Birds of Gunnison and Cub islands, Great Salt Lake, Utah

Normal 0 false false false EN-US X-NONE X-NONE 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-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;} A total of 87 avian species were recorded on islands of Great Salt Lake by Behle, with 17 observed on Gunnison and Cub islands. This paper presents sightings and salvaged carcasses recorded on Gunnison and Cub islands, 1972 &ndash; 1974. Of the 112 species observed, 95 are first records for Gunnison and Cub islands and 49 are first records on or near any island of Great Salt Lake. Over 90 percent of species observed on the islands were transients.     

Selective herbivory by the desert woodrat ( Neotoma lepida ) on Joshua trees ( Yucca brevifolia )

We studied herbivory by the desert woodrat ( Neotoma lepida ) on Joshua trees ( Yucca brevifolia ) in the Mojave Desert to determine whether N. lepida fed selectively based on leaf nitrogen content. We measured leaf nitrogen content and the location and amount of herbivory by woodrats on Y. brevifolia trees in southwestern Utah, USA. Neotoma lepida removed the outer tips of leaves (1/3 to 2/3 of total leaf length) but left leaf bases, which had lower nitrogen content, uneaten. Herbivory by N. lepida also was concentrated on rosettes that were oriented south, and these had significantly higher nitrogen content than rosettes that were oriented north. Finally, N. lepida fed more on trees that had higher mean leaf nitrogen contents. Thus, N. lepida selectively foraged among leaf parts, among rosettes of leaves, and among trees of Y. brevifolia , and disproportionate foraging was correlated with nitrogen content of leaves.     

The alpine butterflies of Castle Peak, Nevada County, California

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;} The west slope of Basin and Castle peaks and the ridge between them displays a wind - generated tree line below 8500 ft, with dry alpine fell - field vegetation above. The butterfly fauna, although depauperate compared to that of the High Sierra farther south, includes some truly boreal elements such as Oeneis ivallda, Plebeius shasta, and Hesperia nevada. These species commonly occur 1500 to 4000 ft higher in the southern Sierra. &nbsp;&nbsp;     

Use of a secondary nest in Great Basin Desert thatch ants ( Formica obscuripes Forel)

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.     

Variation in leaf anatomy and CO 2 assimilation in Sitanion hystrix ecotypes

Collections of Sitanion hystrix known to differ in phenological development, height, dry matter production, and total water use were examined for possible differences in leaf anatomy and in CO 2 assimilation rates. Collections originating in warm, dry habitats produced the narrowest leaves with the fewest veins. Other anatomical characteristics examined were either not different among collections or the differences did not appear to be related to the original habitats. The CO 2 assimilation rates were similar on per-unit weight basis; therefore total assimilation varied as a function of plant size.