Macroscopic features of scurvy in human skeletal remains: A literature synthesis and diagnostic guide

The past two decades have seen a proliferation in bioarchaeological literature on the identification of scurvy, a disease caused by chronic vitamin C deficiency, in ancient human remains. This condition is one of the few nutritional deficiencies that can result in diagnostic osseous lesions. Scurvy is associated with low dietary diversity and its identification in human skeletal remains can provide important contextual information on subsistence strategy, resource allocation, and human-environmental interactions in past populations. A large and robust methodological body of work on the paleopathology of scurvy exists. However, the diagnostic criteria for this disease employed by bioarchaeologists have not always been uniform. Here we draw from previous research on the skeletal manifestations of scurvy in adult and juvenile human skeletal remains and propose a weighted diagnostic system for its identification that takes into account the pathophysiology of the disease, soft tissue anatomy, and clinical research. Using a sample of individuals from the prehistoric Atacama Desert in Northern Chile, we also provide a practical example of how diagnostic value might be assigned to skeletal lesions of the disease that have not been previously described in the literature.     

Differential fragment regeneration in Syntrichia caninervis Mitt. from the Gurbantunggut Desert of China

Fragments of the desert moss Syntrichia caninervis Mitt. were grown on the surface of moistened sand to assess their regeneration capacity. The plant material was collected in two different years (2014 and 2015) and divided into five fragment classifications (stem apices, green leaves, yellow-green leaves, brown leaves and stems). All fragments of the stem apices, green leaves and stems regenerated within 10 days of culture while some fragments of yellow-green leaves (two 2014 fragments and one 2015 fragment) and brown leaves (three 2014 fragments and three 2015 fragments) died. Fragments of stem, stem apices and green leaves regenerated more quickly, produced longer protonemata and more shoots as compared to fragments of yellow-green and brown leaves. These differences were statistically significant but there was no difference in regeneration between the fragments from 2014 and 2015. Differential regeneration and proliferation of different plant fragments has important implications for the clonal propagation of S. caninervis in the Gurbantunggut Desert.     

白尾地鸦的巢址选择

2017年4和5月,在位于新疆塔克拉玛干沙漠南缘的和田地区民丰县对白尾地鸦（Podoces bidduphi）的巢址选择进行研究。共记录白尾地鸦巢12个,测量了巢参数,用Mann-Whitney U检验分析巢样方与对照样方的差异,用主成分法分析影响白尾地鸦巢址选择的主要因子。结果显示：1）白尾地鸦巢多筑于绿洲边缘的柽柳（Tamarix）灌丛,巢距地面高（109.1 ± 13.2）cm,巢深（8.5 ± 0.5）cm,巢厚（3.8 ± 0.4）cm,内径（13.9 ± 0.9）cm,外径（21.6 ± 1.3）cm;2）巢样方的植被物种数和植被盖度远高于对照样方;3）影响白尾地鸦巢址选择的主要因素为植被物种数及干扰,其中干扰主要指距道路以及距居民点的距离。综上所述,白尾地鸦的巢址选择受食物等生存需求和躲避干扰等安全因素的双重影响,是生存与繁殖权衡的结果。     

The pollination of merremia palmeri (Convolvulaceae): can hawk moths be trusted?

The reproductive biology of Merremia palmeri and the pollination efficiency of its insect visitors were examined for a Sonoran Desert population in northwestern Mexico. Pollen transfer experiments proved that the plant is self-incompatible. Reproduction is, therefore, dependent upon reliable visitation by the primary pollinators, hawk moths. Many aspects of the floral structure are typical of sphingophilous flowers, and the time of flower opening and nectar secretion corresponded to the period of greatest hawk moth activity. A single hawk moth visit to a flower could be sufficient for successful fertilization. Additional visits up to five increased percentage fruit set, but flowers that received six or more visits had lower fruit and seed set. Neither the number of moth visits nor fruit and seed set were correlated with temperature or relative humidity. Over the course of the study >55% of flowers set fruit. We conclude that hawk moths are reliable and efficient pollinators for M. palmeri in a warm desert habitat.     

Monosoonal precipitation responses of shrubs in a cold desert community on the Colorado Plateau

South-eastern Utah forms a northern border for the region currently influenced by the Arizona monosoonal system, which feeds moisture and summer precipitation into western North America. One major consequence predicted by global climate change scenarios is an intensification of monosoonal (summer) precipitation in the aridland areas of the western United States. We examined the capacity of dominant perennial shrubs in a Colorado Plateau cold desert ecosystem of southern Utah, United States, to use summer moisture inputs. We simulated increases of 25 and 50 mm summer rain events on Atriplex canescens, Artemisia filifolia, Chrysothamnus nauseosus, Coleogyne ramosissima, and Vanclevea stylosa, in July and September with an isotopically enriched water (enriched in deuterium but not ¹⁸O). The uptake of this artificial water source was estimated by analyzing hydrogen and oxygen isotope ratios of stem water. The predawn and midday xylem water potentials and foliar carbon isotope discrimination were measured to estimate changes in water status and water-use efficiency. At. canescens and Ch. nauseosus showed little if any uptake of summer rains in either July or September. The predawn and midday xylem water potentials for control and treatment plants of these two species were not significantly different from each other. For A. filifolia and V. stylosa, up to 50% of xylem water was from the simulated summer rain, but the predawn and midday xylem water potentials were not significantly affected by the additional summer moisture input. In contrast, C. ramosissima showed significant uptake of the simulated summer rain (>50% of xylem water was from the artificial summer rain) and an increase in both predawn and midday water potentials. The percent uptake of simulated summer rain was greater when those rains were applied in September than in July, implying that high soil temperature in midsummer may in some way inhibit water uptake. Foliar carbon isotope discrimination increased significantly in the three shrubs taking up simulated summer rain, but pre-treatment differences in the absolute discrimination values were maintained among species. The ecological implications of our results are discussed in terms of the dynamics of this desert community in response to changes in the frequency and dependability of summer rains that might be associated with a northward shift in the Arizona monsoon boundary.     

Major plant communities of warm North American deserts

Abstract. A syntaxonomic study of the major plant communities in neotropical North American deserts (Sonoran, Mojave and Baja California Deserts) is presented. The field method of the Braun-Blanquet approach was combined with a numerical syntaxonomical analysis (cluster analysis and principal coordinate ordination). 21 associations are described for the first time: Ambrosio chenopodifoliae-Larreetum tridentatae, Acamptopappo sphaerocephali-Larreetum tridentatae, Hymenocleo monogyrae-Baccharidetum glutinosae, Bergerocacto emoryi-Agavetum shawii, Burseretum hindsianomicrophyllae, Cercidio microphylli-Carnegieetum giganteae, Bursero microphyllae-Cyrtocarpetum edulis, Hymenocleo salsolae-Daleetum spinosae, Echinocereo engelmannii-Agavetum deserti, Euphorbio californicae-Fouquierietum diguetii, Fouquierio splendentis-Larreetum tridentatae, Agavo cerulatae-Idrietum columnaris, Mascagnio macropterae-Lysilometum candidae, Maytenetum phyllanthoidis, Opuntio basilaris-Larreetum tridentatae, Prosopidetum torreyanae, Roso minutifoliae-Aesculetum parryi, Opuntio taponae-Agavetum subcerulatae, Tidestromio oblongifoliae-Atriplicetum hymenelytrae, Eurotio lanatae-Larreetum tridentatae and Yucco validae-Fouquierietum diguetii. Some associations include subassociations. Ecological, biogeographical and floristic bioclimatic data are given for each association.     

Viable bacterial aerosol particle size distributions in the midsummer atmosphere at an isolated location in the high desert chaparral

The viable bacterial particle size distribution in the atmosphere at the Hanford Nuclear Reservation, Richland, WA during two, 1-week periods in June 1992, was observed at three intervals during the day (morning, midday and evening) and at three heights (2, 4, and 8 m) above ground level. The distributions were significantly different (P=0.01) between the two, 1-week sampling periods and between morning, midday, and evening observations, but not between the three heights. Approximately 30 to 50% fell into the largest particle size category; 7.0µm aerodynamic diameter. All particle size categories were at their minimum bacterial concentration at around noon, with the lowest concentrations in the smaller size categories (<2.1µm aerodynamic diameter). This suggests, that at this high desert location, solar radiation (SR) damage to airborne bacteria is particle size discriminatory. There is a relatively greater effect on the smaller size categories at midday and a relatively lesser effect in the morning and evening.     

A 10-year demographic study of rabbitbrush (Chrysothamnus nauseosus): growth,survival and water limitation

A population of 126 adult rabbitbrush (Chrysothamnus nauseosus var. consimilis) was followed for 10 consecutive years from 1983 through 1992 in a sanddune ecosytem on the north shore of Mono Lake, California. The study area received an average (1981–1992) of 160 mm total annual precipitation of which 55 mm fell from April through October, making this site drier than other known sites in the Great Basin desert where C. nauseosus occurs. Cover of all shrubs was 18.0%, and that of C. nauseosus 7.5%, in the 3077 m² study plot. Water was limiting for this population of C. nauseosus, exerting large effects on new canopy growth and reproductive effort in a given year, on survival, and on establishment of juveniles into the adult population. Growth and survivorship of the adult shrubs were significantly correlated with the depth to ground water, which varied from 3.6 to 6.0 m below the surface during the study, and not with any measure of precipitation in a given year or adjacent years. Shrubs in this population exhibited a net decrease in size between 1983 and 1992. The region experienced a significant drought from 1987 onwards, with some increase in precipitation after 1990. Mortality of shrubs began in 1987 and reached 22% by 1992. Individuals that died were smaller on average initially than individuals surviving throughout the study: 50% or more of the individuals having 4000 cm² of canopy or less at the start of the study died by 1992. Elevation (m msl) of each shrub in the study area, presumably correlated with depth to ground water, had no effect on growth but a weak effect on survival during the study period. Specific microsite had significant effects, with shrubs on steep slopes being smaller, having more negative growth slopes, and being more likely to die during the drought compared to individuals occurring on flatter gradients. Recruiment of juveniles into the population did not occur after 1985. Competition between shrubs could not be definitively demonstrated during the study, but only indirect tests for competition were used. Adult C. nauseosus and adults of all species combined (Sarcobatus vermiculatus with 9.6% cover, Tetradymia tetrameres with 0.8% cover and Chrysothamnus viscidiflorus with 0.02% cover) were randomly distributed, failing to support the hypothesis of competition if competition for water results in a uniform distribution of shrubs. Moreover, comparison of the spatial dispersion of C. nauseosus individuals before (1985) and after (1992) mortality did not reveal competitive thinning toward uniformity. On the other hand, larger individuals were farther from their nearest neighbor than were smaller individuals, an effect postulated to result from competitive thinning.     

Methanogenesis in Arizona,USA dryland streams

Methanogenesis was studied in five streams of central and southern Arizona by examining the distribution of methane in interstitial water and evasion of methane in three subsystems (hyporheic, parafluvial and bank sediments). In Sycamore Creek, the primary study site (studied during summer and early autumn), methane content of interstitial water exhibited a distinct spatial pattern. In hyporheic (sediments beneath the wetted channel) and parfluvial zones (active channel sediments lateral to the wetted channel), which were well oxygenated due to high hydrologic exchange with the surface stream and had little particulate organic matter (POM), interstitial methane concentration averaged only 0.03 mgCH₄-C/L. Bank sediments (interface between the active channel and riparian zone), in contrast, which were typically vegetated, had high POM, low hydrologic exchange and concomitantly low dissolved oxygen levels, had interstitial concentration averaging 1.5 mgCH4-C/L. Methane emission from Sycamore Creek, similar to methane concentration, averaged only 3.7 mgCH₄-C·m⁻²·d⁻¹ from hyporheic and parafluvial zones as opposed to 170 mgCH₄-C·m⁻²·d⁻¹ from anoxic bank sediments. Methane in four additional streams sampled (one sampling date during late winter) was low and exhibited little spatial variation most likely due to cooler stream temperatures. Interstitial methane in parafluvial and bank sediments of all four streams ranged from only 0.005 to 0.1 mgCH₄-C/L. Similarly methane evasion was also low from these streams varying from 0 to 5.7 mgCH₄-C·m⁻²·d⁻¹. The effects of organic matter and temperature on methanogenesis were further examined by experimentally manipulating POM and temperature in stoppered flasks filled with hyporheic sediments and stream water. Methane production significantly increased with all independent variables. Methane production is greatest in bank sediments that are relatively isolated hydrologically and lowest in hyporheic and parafluvial sediments that are interactive with the surface stream.     

Resource partitioning between ungulate populations in arid environments

Herbivores are major drivers of ecosystem structure, diversity, and function. Resilient ecosystems therefore require viable herbivore populations in a sustainable balance with environmental resource availability. This balance is becoming harder to achieve, with increasingly threatened species reliant on small protected areas in increasingly harsh and unpredictable environments. Arid environments in North Africa exemplify this situation, featuring a biologically distinct species assemblage exposed to extreme and volatile conditions, including habitat loss and climate change‐associated threats. Here, we implement an integrated likelihood approach to relate scimitar‐horned oryx (Oryx dammah) and dorcas gazelle (Gazella dorcas) density, via dung distance sampling, to habitat, predator, and geographic correlates in Dghoumes National Park, Tunisia. We show how two threatened sympatric ungulates partition resources on the habitat axis, exhibiting nonuniform responses to the same vegetation gradient. Scimitar‐horned oryx were positively associated with plant species richness, selecting for vegetated ephemeral watercourses (wadis) dominated by herbaceous cover. Conversely, dorcas gazelle were negatively associated with vegetation density (herbaceous height, litter cover, and herbaceous cover), selecting instead for rocky plains with sparse vegetation. We suggest that adequate plant species richness should be a prerequisite for areas proposed for future ungulate reintroductions in arid and semi‐arid environments. This evidence will inform adaptive management of reintroduced ungulates in protected environments, helping managers and planners design sustainable ecosystems and effective conservation programs.