Synchrony of Seed Dispersal, Hydrology and Local Climate in a Semi-arid River Reach in California

The temporal availability of propagules is a critical factor in sustaining pioneer riparian tree populations along snowmelt-driven rivers because seedling establishment is strongly linked to seasonal hydrology. River regulation in semi-arid regions threatens to decouple seed development and dispersal from the discharge regime to which they evolved. Using the lower Tuolumne River as a model system, we quantified and modeled propagule availability for Populus fremontii (POFR), Salix gooddingii (SAGO), and Salix exigua (SAEX), the tree and shrub species that dominate near-channel riparian stands in the San Joaquin Basin, CA. A degree-day model was fit to field data of seasonal seed density and local temperature from three sites in 2002–2004 to predict the onset of the peak dispersal period. To evaluate historical synchrony of seed dispersal and seasonal river hydrology, we compared peak spring runoff timing to modeled peak seed release periods for the last 75 years. The peak seed release period began on May 15 for POFR (range April 23–June 10), May 30 for SAGO (range May 19–June 11) and May 31 for SAEX (range May 8–June 30). Degree-day models for the onset of seed release reduced prediction error by 40–67% over day-of-year means; the models predicted best the interannual, versus site-to-site, variation in timing. The historical analysis suggests that POFR seed release coincided with peak runoff in almost all years, whereas SAGO and SAEX dispersal occurred during the spring flood recession. The degree-day modeling approach reduce uncertainty in dispersal timing and shows potential for guiding flow releases on regulated rivers to increase riparian tree recruitment at the lowest water cost.     

Gas vesicles isolated from Halobacterium cells by lysis in hypotonic solution are structurally weakened

Analysis of pressure-collapse curves of Halobacterium cells containing gas vesicles and of gas vesicles released from such cells by hypotonic lysis shows that the isolated gas vesicles are considerably weaker than those present within the cells: their mean critical collapse pressure was around 0.049-0.058 MPa, as compared to 0.082-0.095 MPa for intact cells. The hypotonic lysis procedure, which is widely used for the isolation of gas vesicles from members of the Halobacteriaceae, thus damages the mechanical properties of the vesicles. The phenomenon can possibly be attributed to the loss of one or more structural gas vesicle proteins such as GvpC, the protein that strengthens the vesicles built of GvpA subunits: Halobacterium GvpC is a highly acidic, typically "halophilic" protein, expected to denature in the absence of molar concentrations of salt.     

Bacteriological activity in unfiltered calf sera collected for tissue culture use

Summary Bacteriological tests were made on 24 lots of unfiltered calf serum collected for subsequent use as a component of tissue culture media. The examination included the isolation and identification of bacteria, assay of phages, and demonstration of endotoxin material. Only Gram-positive bacteria were isolated and 96% of the sera were contaminated with bacteria. The prevalent strains of bacteria found wereBacillus species and streptococci and 63% of the sera coagulatedLimulus amebocyte lysate. More than 90% of the lots contained phages demonstrable with the C-3000 strain ofEscherichia coli. Only one lot of the serum was found to be free from bacteria, phages, and endotoxin by the tests used.     

Advantage of using inosine at the 3' termini of 16S rRNA gene universal primers for the study of microbial diversity

To overcome the shortcomings of universal 16S rRNA gene primers 8F and 907R when studying the diversity of complex microbial communities, the 3' termini of both primers were replaced with inosine. A comparison of the clone libraries derived using both primer sets showed seven bacterial phyla amplified by the altered primer set (8F-I/907R-I) whereas the original set amplified sequences belonging almost exclusively to Proteobacteria (95.8%). Sequences belonging to Firmicutes (42.6%) and Thermotogae (9.3%) were more abundant in a library obtained by using 8F-I/907R-I at a PCR annealing temperature of 54 degrees C, while Proteobacteria sequences were more frequent (62.7%) in a library obtained at 50 degrees C, somewhat resembling the result obtained using the original primer set. The increased diversity revealed by using primers 8F-I/907R-I confirms the usefulness of primers with inosine at the 3' termini in studying the microbial diversity of environmental samples.     

Calmodulin supports the force-generating function in desensitized muscle fibers

Externally added calmodulin (CaM) restored Ca2+ regulation for the tension development by skeletal muscle fibers of hamster and rabbit desensitized by the troponin C (TnC) extraction treatment. CaM produced this action by combining with the TnC-denuded sites in the fiber. However, the binding properties differed strikingly from TnC: unlike TnC, CaM binding required the continued presence of Ca2+ and the bound portion was completely released with EGTA in the physiological milieu. The maximal uptake was 1.7 g of CaM/kg of muscle in the present study. The apparent Ca2+ sensitivity for force development with 200 micrograms/ml CaM in the solution was lower than in the native fiber or in the TnC-loaded fiber. The apparent association constant for CaM binding to the TnC-denuded sites was found as 4.9 x 10(5) M-1, and the extrapolated maximum force (Fmax) with CaM was close to PO. The intrinsic CaM level in intact muscle was also measured and was 18.6 mg/kg, amounting to about 1% of the total TnC or the CaM uptake by TnC-denuded fibers. The intrinsic CaM was not dislodged by EDTA treatment, indicating tight binding and suggesting that it exists in a separate pool from the vacated TnC sites adsorbing externally added CaM. The stringent Ca+ dependence of the CaM adsorption to TnC sites in the regulatory complex in the fiber supports the view that the evolutionary replacement of residues in the amino terminus helix portion of the "EF-hand" motif of site IV may be critical for the functional specialization by TnC.     

Naukan ethnobotany in post-Soviet times: lost edibles and new medicinals

Background

This study focuses on health-related plant use among speakers of the critically endangered Naukan language (Inuit-Yupik-Unangan family) in the Russian Far East. The Naukan people were forced, in 1958, under Soviet consolidation, to move from their original settlement on Cape Dezhnev, leading to significant changes in spiritual worldview, subsistence, social structure, and language proficiency in the years that followed. Here, we focus on changes that elders report in their edible, medicinal, and spiritual uses of local plant species since their childhood.

Methods

The authors worked from 2014 to 2016 in the villages of Lavrentiya, Lorino, and Uelen, in the Chukotskiy district of the Chukotka autonomous region, directly adjacent to the Bering Strait. We conducted structured interviews, using an oral history approach, along with participant observation and collection of voucher specimens from the local arctic tundra. Those with Naukan names and uses represent 42 species in 25 families.

Results

Participants reported a decrease of 13% in the number of edible species that people currently harvest, from what they recall harvesting in their youth. On the other hand, the number of local species considered to be medicinal has actually increased by 225%. Current and past Naukan medicinal practices diverge in some notable ways from those of neighboring societies on the Alaskan side of the Bering Strait. Most of the spiritual significance of local plants species is remembered by only a few elders.

Conclusions

Naukan elders explained the large increase in use of medicinal plants by noting that their original concept of medicine emphasized prevention and that illnesses were often assigned a spiritual rather than physical cause. Increased integration with ethnic Russians after moving from Naukan led to the adoption not only of new plant uses, but also of an entirely different, more naturalistic way of viewing illness and treatment.

     

GENETICS OF STERILITY IN HYBRIDS BETWEEN TWO SUBSPECIES OF DROSOPHILA

Hybrids between D. pseudoobscura bogotana and D. pseudoobscura pseudoobscura are fertile except for males produced in one of the two reciprocal crosses. As there is no premating isolation between these subspecies, nonreciprocal male sterility represents the first step in speciation. Genetic analysis reveals two causes of hybrid F₁ sterility: a maternal effect and incompatibilities between chromosomes within males. The maternal effect appears to play the greatest role in hybrid sterility. The X chromosome has the largest effect on fertility of any chromosome, a ubiquitous result in analyses of hybrid sterility and inviability in Drosophila. This effect is entirely attributable to a region comprising less than 30% of the X chromosome. These results are compared to those from a similar study of D. pseudoobscura-D. persimilis hybrids, an older and more reproductively isolated species pair in the same lineage. Such comparisons may allow one to identify the genetic changes characterizing the early versus late stages of speciation.