Seasonal changes of selected secondary plant products in Chrysothamnus nauseosus ssp. turbinatus

Previously, physiological studies of rubber and resin production during the growing season of Chrysothamnus nausceosus ssp. turbinatus indicated a negative correlation between rubber and resin content. The resin was highest in the spring and lowest in the summer, whereas rubber was highest in the summer and lowest in the spring. Individual compounds were followed during the growing season to see if they correlated with the rubber or resin trend. The total compounds in the cyclohexane fraction followed the resin pattern. Individual compounds varied in their changes during the growing season. Limonene, for example, was negatively correlated with rubber production, whereas β cubebene was positively correlated. The possible metabolic pathways between resin and rubber are discussed.     

Botanical content of black-tailed jackrabbit diets on semidesert rangeland

Botanical content of black-tailed jackrabbit diets was determined by microhistological examination of fecal samples collected from six different vegetation types in southern New Mexico on three dates. Grasses comprised the largest component of the jackrabbit diets, with dropseed species ( Sporobolus spp.) and black grama ( Bouteloua eriopoda ) the most abundant grasses in the diets. Leatherweed croton ( Croton pottsii ) and silverleaf nightshade ( Solanum elaeagnifolium ) were important forbs on most vegetation types. Diet composition varied in response to season and vegetation type. Grasses were important during the summer growing season, while forbs were selected during their growing season (summer or winter-spring). Shrubs were less abundant in the diet than grasses and forbs.     

Arbuscular mycorrhizae in thermal-influenced soils in Yellowstone National Park

Mycorrhizae are common plant-fungal symbioses occurring in most land plants. Despite their ubiquity, little is known about the distribution of arbuscular mycorrhizae (AM) in extreme environments. We surveyed for the presence of AM in thermal sites in Yellowstone National Park (YNP) where soils are characterized by extreme pHs, elevated temperatures, and toxic element concentrations. Plants at 5 sites, growing in soils with rooting-zone temperatures up to 48°C and soil pH values as low as 3.4, were mycorrhizal (colonization levels from 4% to 34%). Soils from a sparsely vegetated thermal area and an adjacent, continuously vegetated transition area differed significantly in rooting-zone temperature (35°C vs. 26°C), acidity (pH 3.8 vs. 5.4), electrical conductivity (2.22 vs. 0.49 mmhos cm -1 ), Fe (181.3 vs. 48.5 mg kg -1 ),Mn (7.2 vs. 98.2 mg kg -1 ), and Zn (2.3 vs. 4.5 mg kg -1 ). Mycorrhizal infectivity potential (MIP) was 77% greater in the transition soils, with colonization levels of 26% and 46% in thermal and transition soils, respectively. Furthermore, colonization of Agrostis scabra , Dichanthelium lanuginosum , and Mimulus guttatus was found to be consistently high throughout the growing season (from 48% to 72%). It is possible that AM are essential for plant life on the edge of thermal areas, and that either or both symbionts are specifically adapted to their environment. Further research is required to elucidate AM function in and specific adaptations to YNP's thermal areas.     

Observations on seasonal variation in desert arthropods in central Nevada

Pitfall and Malaise trap collections from terrestrial arthropod populations in central Nevada were analyzed for four trapping periods during the 1978 growing season. Mites (Acarina) and ants (Formicidae) were the taxa represented by the largest numbers of individuals in pitfall trap collections throughout the season; Malaise collections were composed mainly of aerial taxa (largely Diptera and Hymenoptera). Peak arthropod abundance was recorded during mid-June. Collection diversities for both trapping methods were generally low due to the abundance of a few taxa. Evidence for spatial heterogeneity in arthropod populations was meager; temporal heterogeneity in these populations, however, was more apparent.     

Exceptional fish yield in a mid-elevation Utah trout reservoir: effects of angling regulations

We used creel surveys to evaluate how a change from a 6-mon to a year-round fishing season affected the sport fish harvest in East Canyon Reservoir (Utah), a 277-ha mesoeutrophic system. Under the year-round season, fishing effort was 840 angler-h . ha -1. yr -1 , and 360 trout ha -1 were captured. Catch rates were proportional to estimated trout densities in the reservoir, ranging from 1.06 during the winter ice fishery, to 0.18 fish angler -1. h -1 in July. Ninety-nine percent of fish harvested were rainbow trout ( Oncorhynchus myskiss ). Thirty-two percent of the 300,000 75-mm fingerling trout stocked annually were captured by anglers within 2.5 yr, but return rates varied with the strain and/or size of trout stocked. Annual fish yield was 102 kg/ha, among the highest yet reported for a temperate zone, lacustrine system. Extending fishing from a 6-mon season to year-round increased the number of fish captured and provided almost twice as many hours of recreational fishing in the reservoir. The harvest period was changed from traditional spring-summer months to primarily a winter-spring fishery because relatively few trout survived for more than 6 mon after reaching harvestable size. Although salmonid production in East Canyon Reservoir is very high, the fishery is in a precarious state because high primary productivity driven, in part, by cultural cutrophication, makes water quality suboptimal during midsummer.     

Anuran assemblage composition and distribution at a modified environment in Três Marias reservoir,south-eastern Brazil

We assessed the influence of environmental features on anuran species distribution in Pirapitinga, an island formed by the filling of a reservoir in south-eastern Brazil. We investigated whether the species exhibited preferences towards certain habitat types and the existence of niche partitioning. We recorded 474 individuals from seven species. Although considered as generalists, these species were not distributed randomly, but according to specific habitat preferences that happened to be fulfilled by the shores of the reservoir. Niche overlaps were higher than expected by chance during the wet season, when most species were active, but not different from random during the dry season. Environmental variables seemed to be important and promote aggregation of several anuran species at the same habitats. Interspecific signals may be used for this purpose, and competition is probably small or less important than the benefits provided by choosing the most suitable habitats in this impacted environment.     

Diet and food-niche breadth of Burrowing Owls ( Athene cunicularia ) in the Imperial Valley, California

Burrowing Owls ( Athene cunicularia ) occupy intensively managed agricultural areas within the Imperial Valley of California, where they occur at high densities relative to other areas in the state, and yet reproductive rates are often low. Understanding diet and food-niche breadth may lead to insights into factors contributing to their poor reproductive performance. We tested the relative contribution of sex, year, and season on diet composition and food-niche breadth from analyses of stomach contents of adult Burrowing Owls ( n = 53). Orthoptera dominated the diet; it accounted for 58.9% of the total number of prey items in all stomachs and was found in 98.2% of all samples. Rodents, a source of potentially limiting dietary calcium, were found in only 2 stomachs. We detected yearly and seasonal effects on estimated food-niche breadth. Mean food niche for the breeding season was broader (antilog of Shannons index: 2.38 ± 0.15) and more even (Pielous index: 0.67 ± 0.06) than for the nonbreeding season (1.83 ± 0.13, 0.49 ± 0.07, respectively) partially because of a greater frequency of Araneida, Isopoda, Lepidoptera, and Solpugida in the diet during the breeding season. Mean food-niche breadth for 1997 (2.25 ± 0.23) was broader than during 1994, 1995, and 1996 (2.07 ± 0.23, 1.98 ± 0.20, and 1.82 ± 0.40, respectively) because of a greater frequency of Araneida, Dermaptera, Isopoda, Lepidoptera, and Solpugida. These results, and auxiliary diet information, suggest rodents were infrequent in the diet of Burrowing Owls in the Imperial Valley and may help explain their lower reproductive success relative to other areas of California.     

Population biology of Sphaeroma serratum Fabricius (Isopoda,Flabellifera) at the Port of Mar del Plata,Argentina

Variations in size distribution, sex ratio, fecundity and morph frequencies in a population of Sphaeroma serratum were studied year-round. Changes in size distribution are most marked during the breeding season. Growth is arrested during the winter months. Young are produced throughout the summer; these overwinter, reproduce and then die. Differences in size of mature males suggest an effect of the timing of birth on life-span. Females are able to produce two broods. Offspring number is positively correlated with female size. Brood pouch mortality is estimated at 39%. Marked changes in sex ratio within the breeding season are thought to be artifacts due to sexual differences in behaviour. Comparison of reproductive traits of this, and other, populations shows a latitudinal pattern related to the duration of the warm season. Analysis of morph frequencies revealed similarities with European populations so far studied.     

Seasonal patterns of arthropod diversity and abundance on big sagebrush, Artemisia tridentata

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.     

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 –0.2 MPa.     

Body size, organ size, and sex ratios in adult and yearling Belding ground squirrels

A five - year study of Belding ground squirrels was conducted at high altitude in the Sierra Nevada. Body weight and body length varied seasonally depending upon the fat depletion - deposition cycle, age, and sex. Adult males tended to be heavier and longer than adult females, particularly in the last half of the active season. A similar pattern was present in yearlings. Yearling squirrels were often distinguishable from adults on the basis of body size. Mean body weights were greater in adults throughout the season, and mean body lengths were greater in adults through the first half of the season. Adults also had larger internal organs than yearlings at the beginning of the season. In liver and heart this difference was sustained. Sex ratios in adults and in yearlings were 1:1 but there was considerable spatial and temporal asymmetry in distribution of the sexes. Males tended to live in areas peripheral to lush meadows occupied by females and young.       

Plant adaptation in the Great Basin and Colorado Plateau

Adaptive features of plants of the Great Basin are reviewed. The combination of cold winters and an arid to semiarid precipitation regime results in the distinguishing features of the vegetation in the Great Basin and Colorado Plateau. The primary effects of these climatic features arise from how they structure the hydrologic regime. Water is the most limiting factor to plant growth, and water is most reliably available in the early spring after winter recharge of soil moisture. This factor determines many characteristics of root morphology, growth phenology of roots and shoots, and photosynthetic physiology. Since winters are typically cold enough to suppress growth, and drought limits growth during the summer, the cool temperatures characteristic of the peak growing season are the second most important climatic factor influencing plant habit and performance. The combination of several distinct stress periods, including low-temperature stress in winter and spring and high-temperature stress combined with drought in summer, appears to have limited plant habit to a greater degree than found in the warm deserts to the south. Nonetheless, cool growing conditions and a more reliable spring growing season result in higher water-use efficiency and productivity in the vegetation of the cold desert than in warm deserts with equivalent total rainfall amounts. Edaphic factors are also important in structuring communities in these regions, and halophytic communities dominate many landscapes. These halophytic communities of the cold desert share more species in common with warm deserts than do the nonsaline communities. The Colorado Plateau differs from the Great Basin in having greater amounts of summer rainfall, in some regions less predictable rainfall, sandier soils, and streams which drain into river systems rather than closed basins and salt playas. One result of these climatic and edaphic differences is a more important summer growing season on the Colorado Plateau and a somewhat greater diversification of plant habit, phenology, and physiology.     

Spatial patterns of the semi-aquatic rodent Nectomys squamipes in Atlantic forest streams

Nectomys squamipes is a semi-aquatic rodent with a wide geographic range in Brazilian forests and savannas. This species is a host for several parasites associated with aquatic environments, especially Schistosoma mansoni, and thus its spatial pattern may influence some diseases’ patterns. Here we present important aspects of water rat spatial behaviour, including technical and ecological aspects. Water rats were studied by live trapping in rivers and in gallery forests between January 2005 and August 2008, with a total sampling effort of 9511 trap-nights. We also studied some animals through radio tracking and the spool-and-line technique. Water rat movement was distributed evenly between the terrestrial and aquatic environments. Nectomys squamipes occurrence in small tributaries was higher than in larger and lotic rivers. Both home range, the conventional two-dimensional approach, and home length, a one-dimensional approach, proved to be useful to study N. squamipes, depending on the shape of the water body used by the individual. Although Nectomys squamipes’ home length was positively correlated with body weight, sex was also important to explain home length variation; at similar body weights, males have larger home lengths than females. Males explored larger areas during the rainy season, likely in search of females, as this is the water rat reproductive season in Atlantic forest. In contrast, females explored larger areas during the dry season, likely looking for additional food supplies as a result of deficient water rat food supplies during the Atlantic forest dry season. Females overlapped home lengths with more than one male, and males with more than one female, suggesting a promiscuous mating system for this species.     

Effects of water temperature on growth of razorback sucker larvae

I conducted laboratory experiments and fit a response surface regression model to evaluate growth of endangered razorback sucker ( Xyrauchen texanus ) up to 37 days post-hatch. Fish growth at ad libitum ration was positively related to water temperature, and larvae reared at 25.5°C grew about twice as fast in length and 4 times as fast in weight as those at 16.5°C. Growth was intermediate at 19.5°C and 22.5°C. Time required for razorback sucker larvae to exceed 25 mm total length (TL), a potentially important threshold for reduced predation, was 30 days (post-hatch) at 25.5°C, 33 days at 22.5°C, 36 days at 19.5°C, and 41 days at 16.5°C. Time to exceed 25 mm TL increased to 52 days under a low growth rate of 0.29 mm ? d –1 . Faster growth rates could reduce the time that razorback sucker larvae are vulnerable to predation by abundant and co-occurring small-bodied fish and invertebrate predators in nursery areas. Growth of razorback sucker larvae could be enhanced if flow re-regulation at Flaming Gorge Dam and downstream levee removal restored connections between the Green River and its floodplain and increased availability of warm and productive wetlands.     

Field acetylene reduction rates of Lupinus argenteus along an elevational gradient

The effects of elevation and environmental parameters associated with elevation on the dinitrogen fixation rates, N 2 [C 2 H 2 ], of a North American lupine species were evaluated. Lupinus argenteus Pursh plants growing at five elevations on Francis Peak, Utah, were sampled weekly throughout the growing season. The highest elevation site had the greatest frequency of nodulated plants. Influence of the environmental and physiological variables on fixation activity varied with elevation and the mean time of sampling. Soil moisture, nodule dry weight, and air temperature were important. Less than one-half of the observed variation in fixation rates, N 2 [C 2 H 2 ], was accounted for by variation in the associated independent variables. Nevertheless this study documented that nodulated plants of L. argenteus were capable of actively fixing nitrogen at a range of elevations on Francis Peak.     

Colony foundation,nest architecture and demography of a basal fungus‐growing ant,Mycocepurus smithii (Hymenoptera,Formicidae)

The genus Mycocepurus is a phylogenetically basal attine ant, so studies of its biology may provide insight into the evolution of behaviours associated with fungus‐growing that characterize the tribe Attini. Mycocepurus smithii from Puerto Rico produces sexual females from July to September, but no males were observed in 2 years of observations, confirming previous observations elsewhere. Colonies were founded between July and August and most nests were haplometrotic (85% of 74 nests). After excavating a tunnel and small chamber, a foundress queen inserted her fore wings into the ceiling and used the wing surfaces as a platform on which the incipient fungal garden was grown. Foundresses foraged for substrate to grow the fungus garden. Growth of incipient colonies was slow: the first workers emerged 2–5 months after colony founding and, after 8 months, colonies contained on average only a single worker.     

Description and ecology of a new species of sun spider (Arachnida: Solifugae) from the Brazilian Cerrado

A new species of solifuge from São Paulo State, south-eastern Brazil, is described, together with its phenology, habitat use, activity pattern and the effect of fire on the population. Mummucia coaraciandu n. sp. differs from other Mummuciidae in cheliceral dentition and pleurite coloration. Over a one-year period, 649 individuals of M. coaraciandu were captured in 72 pitfall traps distributed in three Cerrado physiognomies: borders of gallery forest (N=53), campo sujo (N=561) and campo cerrado (N=35). The species is diurnal and showed two peaks of surface activity during the year: the highest peak occurred in the cold–dry season (June to July) and the smaller peak in the middle of the warm–wet season (December to February). The number of individuals per trap was negatively correlated with the mean monthly temperature, but showed no correlation with the monthly precipitation. The sex ratio was male-biased (7:1) and the number of males trapped was positively correlated with the number of reproductive females. More individuals were trapped in burned areas when compared with unburned areas 1 month after the fire. This difference between the two areas was not observed 1 month before and 3–4 months after the passage of the fire (when the vegetation had recovered). Mummucia coaraciandu is the second solifuge described from the Brazilian Cerrado and its ecology is very similar to that of Mummucia mauryi from Caatinga vegetation.     

Natural history of the African riverine tiger beetle Chaetodera regalis (Dejean) (Coleoptera: Cicindelidae)

The tiger beetle Chaetodera regalis (Dejean) (Coleoptera: Cicindelidae) is widely distributed throughout sub-Saharan Africa. We studied activity patterns, ecological interactions, and behaviour of this species along four major rivers in Kruger National Park, South Africa. During the dry season, small numbers of adult beetles are found on sand bars along perennial rivers. In the rainy season, adults are found in large numbers on a broad spectrum of substrates (including clays, coarse and fine sands and gravels, and black organic soils) and geomorphological features (sand flats, mud flats, sand bars, beaches, riverbanks, and dry and wet sandy streambeds) in riverine areas. Predatory, defensive, thermoregulatory, and reproductive behaviours are described. This species may prove to be a useful indicator of the health of African riverine systems: adults are abundant in high-quality riverine areas; adults and larvae may be adversely affected by human activities; and adults are easily detected, even by novice surveyors.     

Environmental factors in relation to the salt content of Salicornia pacifica var. utahensis

The stability of the salt content in Salicornia pacifica Standl. var. utahensis (Tidestrom) Munz in relation to environmental changes was investigated. Salicornia pacifica communities have a characteristic soil pH of 7.5 to 8.0 ± 0.2 and a constant subsurface soil moisture level of 25 to 35 percent. The ion content in the tissue of S. pacifica remained constant despite increased moisture stress throughout the growing season. The concentrations of the salts were significantly higher in the surface soil layers than in the subsurface layers around the roots. Normal metabolic processes in the tissues of S. pacifica appear to occur even though some fluctuations in the ionic balance and concentration of ions in the plant occur.