Harsh Habitats Research Articles

Isolation of pyomelanin from bacteria and evidences showing its synthesis by 4-hydroxyphenylpyruvate dioxygenase enzyme encoded by hppD gene

Various types of pigments are produced by different bacterial species and play multifunctional role including their role as a protective agent against environmental stresses. The present study deals with the isolation and characterization of melanin pigment from bacteria. Three isolates showed pigment production and identified as Klebsiella pneumoniae S-1, Alcaligenes faecalis PBI and Enterobacter sp. ABI on the basis of 16S rRNA gene sequencing. The maximum production of brown pigment (λmax 405 nm) was attained after 6 days of growth in liquid medium containing 3 g L−1 of l-tyrosine. Solubility test, FTIR and ESI-MS analysis suggested the nature of pigment as melanin. Identity of pigment type from all the three bacteria was made by HPLC analysis, results showed the presence of homogentisic acid (HGA), a precursor of pyomelanin. All the bacteria showed high activity of 4-hydroxyphenylpyruvate dioxygenase (HPPD) suggesting its role in HGA synthesis. PCR amplification of gene(s) also showed the presence of 4-hydroxyphenylpyruvate dioxygenase (hppD) gene coding for HPPD enzyme suggesting its role in pyomelanin synthesis. This study deals with only three bacterial isolates, isolation of such pigment from a large number of bacteria growing in harsh habitats may prove useful in finding novel type of melanin.

A glyphosate-based herbicide reduces fertility, embryonic upper thermal tolerance and alters embryonic diapause of the threatened annual fish Austrolebias nigrofasciatus

Roundup is the most popular glyphosate-based herbicide (GBH) worldwide. These formulations kill a wide range of plants. Despite that, non-target species can be jeopardized by GBH, such as the annual fish Austrolebias nigrofasciatus. This species occurs in wetlands that dries annually. Key-adaptations permit them to live in such harsh habitats, e. i. Elevated fertility, drought-tolerant diapausing embryos and elevated thermal tolerance. We aimed to evaluate acute (96 h) effects of Roundup exposure (0.36 or 3.62 mg a. e./L) in reproduction, diapause pattern and embryonic upper thermal tolerance (EUTT) of A. nigrofasciatus. For such, we evaluated the number and diameter of embryos produced by exposed fish. Also, recently fertilized embryos were exposed and its diapause pattern was evaluated. Following 15 post exposure days (PED), we evaluated the number of somite pairs and following 30, 35 and 40 PED we evaluated the proportion of pigmented embryos (PPE). Finally, the critical thermal maximum (CTMax) of exposed embryos was assessed. Results demonstrated that couples exposed to 0.36 mg a. e./L Roundup produced less but larger embryos. Similarly, embryos exposed to 3.62 mg a. e./L Roundup had a reduced PPE following 30 PED. Finally, embryos exposed to 0.32 mg a. e./L Roundup had a CTMax reduction of 2.6 °C and were more sensitive to minor increases in heating rates. These results indicate that Roundup have negative outcomes in fish reproduction, embryonic development and EUTT. This information is of particular interest to the conservation of annual fish, considering that those are key-adaptations that permit these animals to survive the harsh impositions of ephemeral wetlands.

基于功能性状评价5种植物对热带珊瑚岛环境的适应性

植被新建是保护和改善热带珊瑚岛生态系统的关键环节，热带珊瑚岛极端干旱生境是影响植物存活和定居的主要限制因子之一，因此选取适生植物对热带珊瑚岛植被新建至关重要。通过测定在海南省文昌市苗圃和热带珊瑚岛上的草海桐（Scaevola taccada）、厚藤（Ipomoea pescaprae）、木麻黄（Casuarina equisetifolia）、花生（Arachis hypogaea）、椰子（Cocos nucifera）5种植物的光合/水力相关功能性状，探讨植物对热带珊瑚岛生境的适应性。研究发现：与对照（文昌苗圃）相比，热带珊瑚岛上的草海桐、厚藤、木麻黄最大光合速率（A_max）均显著升高；除椰子外，其余4种植物的比叶面积（SLA）降低，长期水分利用效率升高（其中木麻黄和花生升高显著）；5种植物的叶片碳含量（LC）均有不同程度降低。此外，厚藤、木麻黄、椰子的叶片导水率（K_leaf）显著升高；厚藤和花生的叶片膨压丧失点（Ψ_tlp）显著降低；厚藤和木麻黄的气孔导度（g_s）显著升高。研究结果表明草海桐、椰子、花生主要通过非气孔调节方式（提高K_leaf，降低Ψ_tlp、SLA等）适应热带珊瑚岛干旱环境；而厚藤和木麻黄同时通过气孔调节（降低g_s）及非气孔调节（提高K_leaf，降低Ψ_tlp、SLA等）两种方式促进植物碳同化和水分利用。综上所述，草海桐、厚藤、木麻黄具有更高的光合能力和水分利用效率，能有效协调碳同化和水分利用，表现出良好的适应能力，适合用于热带珊瑚岛的植被新建。;Functional traits are direct measures of plant responses and adaptations to environmental changes. In this study, we quantified the photosynthetic and hydraulic traits of five plant species (Scaevola taccada, Ipomoea pescaprae, Casuarina equisetifolia, Arachis hypogaea, and Cocos nucifera), which were either grown in a nursery in Wenchang, Hainan Province, China, or transplanted to a coral island that has harsh habitats, such as high solar radiation and low fresh water availability. The maximum photosynthetic rate (A_max) of S. taccada, I. pescaprae, and C. equisetifolia growing on the coral island increased significantly compared to the plants growing in Wenchang nursery. Except for C. nucifera, the other four species on the island had lower specific leaf areas (SLA) and higher long-term water use efficiencies. The leaf carbon content (LC) of the five species on the coral island all decreased. In addition, the leaf hydraulic conductivity (K_leaf) of I. pescaprae, C. equisetifolia, and C. nucifera increased and the leaf turgor loss point (Ψ_tlp) for I. pescaprae, and A. hypogaea decreased significantly. However, the stomatal conductance (g_s) of I. pescaprae and C. equisetifolia significantly increased. Our results demonstrated that S. taccada, A. hypogaea, and C. nucifera adapted to the island environment through non-stomatal regulation, (i.e., an increase in K_leaf, but a decrease in Ψ_tlp and SLA). In contrast, I. pescaprae and C. equisetifolia employed both stomatal regulation (i.e., an decrease in g_s) and non-stomatal regulation (an increase in K_leaf, but a decrease in Ψ_tlp, and SLA) to promote plant carbon assimilation. In conclusion, S. taccada, I. pescaprae, and C. equisetifolia had higher photosynthetic rates and water use efficiencies, which enabled them to cope better with the harsh environmental conditions. Therefore, they are recommended as suitable species for vegetation restoration on tropical coral islands.

Contribution to the knowledge on the flora of Munkhkhairkhan mountain area, Mongolia

The Munkhkhairkhan mountain area is a unique highland ecosystem with a diverse regional alpine flora. This mountain habitat is located at the overlap of different floristic regions: on its western side Kazakhstan–Turan flora is dominating, and on the eastern side East Asian flora is observed. It is known that the whole area has a large number of endemics and rare plant species, because of its specific, harsh habitat conditions. Therefore, the flora of different habitats in the Munkhkhairkhan mountain needs to be investigated and properly protected. Munkhkhairkhan National Park has been founded in 2006, and our survey concentrated on the protected area as well as the surrounding areas of the mountains. All recorded species in this study were based on the collected voucher specimens. Conservation status for remarkable species was also reviewed based on the literature. As a result, we recorded 40 families, 150 genera, and 267 species of vascular plants, including four endemic and 34 subendemic species and 15 species' new distribution notes. Around the Munkhkhairkhan mountain, 16 very rare, 21 rare, eight endangered, and two near threatened species are growing, indicating the high conservation value of this area and the necessity for research.

Isolation of extremely halophilic Archaea from a saline river in the Lut Desert of Iran, moderately resistant to desiccation and gamma radiation

Admittedly, the Lut Desert of Iran has been remained as an unexplored region from a microbiological standpoint. Domain Archaea contains extremophiles that can live in harsh habitats. Extremely halophilic archaea are exposed to different environmental stresses in the hypersaline environments such as high solar irradiance and periodic desiccation. Haloarchaeal diversity in Shoor River, a saline river in the Lut Desert (a salinity of 134.3 g L–1 of dissolved salts), was investigated by a culture-dependent method. A large number of extremely halophilic isolates were obtained and a subset of 59 isolates was considered distinct. Firstly, the isolates were screened for their resistance under desiccation stress in 35 days. Eleven of these strains remained viable during the period in a desiccator containing silica gel. Then, three of them were randomly selected and their resistance against desiccation and ionizing radiation were determined. The isolates MS2, MS17, and MS50 were still recovered after 8 weeks in a desiccator and were moderately resistant to gamma radiation with D10 value between 2 and 3 kGy. Strains MS2, MS17, and MS50 were affiliated with three species in the family Halobacteriaceae using 16S rRNA gene sequence analysis as well as morphological and biochemical characteristics—Haloterrigena jeotgali A29T (99.6% similarity), Natrialba aegyptia 40T (99.4% similarity) and Natrinema pallidum NCIMB 777T (99.3% similarity), respectively. Although resistance to desiccation did not follow the sigmoid survival curve pattern of Deinococcus radiodurans, apparently haloarchaea can show a more resistance to desiccation in more long-term periods of time. This is the first report on isolation of extremely halophilic archaea belonged to the family Halobacteriaceae and their radioresistance and desiccation tolerance properties isolated from the Shoor River.

A Dynamic Flow Regime Supports an Intact Great Plains Stream Fish Assemblage

AbstractIntact native fish assemblages—those with all or most historical taxa present and a strong numerical dominance of native species—are rare in streams and other aquatic systems worldwide. Our sampling during four intervals from 1983 to 2007 showed that the Purgatoire River, a Great Plains stream in eastern Colorado, supported an assemblage that was 99.6% native taxa, and all but one rare species persisted through time. An additional rare Arkansas River native fish colonized the Purgatoire River and was widespread in 2006–2007, and only three nonnative taxa were detected. The perennial Purgatoire River supported all native fishes in the basin, while tributaries supported mainly native fishes that were tolerant of intermittent, harsh habitat. In the Purgatoire River, frequency and abundance of dominant species varied spatially during 2006–2007. Persistence of native fishes was unchanged over time in the Piñon Canyon reach of the river even though abundance varied substantially. Despite the presence of upstream Trinidad Reservoir, which reduced flood peak magnitude and frequency and increased base flows, the flow regime of the river remained flashy, with high, turbid, and unpredictable flood flows. Peak flows resulted from thunderstorms in tributaries of the Purgatoire River downstream from the reservoir or from snowmelt runoff and usually occurred in August or July but also were observed in May and June. We attribute persistence of the native fish assemblage to sustained base flows and, more importantly, to the continued (albeit lower) magnitude and frequency of peak flows and otherwise harsh habitat, which limit invasion by nonnative fishes from upstream and downstream reservoirs. Persistence of the intact native fish assemblage in the Purgatoire River requires maintenance of the dynamic flow regime and prevention of invasions by nonnative fishes, including riverine‐adapted centrarchids like Smallmouth Bass Micropterus dolomieu. Conservation of the Purgatoire River basin should be a priority for ecologists and managers alike given its value as a study system and as habitat for rare fishes.Received July 18, 2016; accepted March 20, 2017 Published online July 11, 2017

Flower-visiting insects observed on the critically endangered alpine plant species Callianthemum kernerianum Freyn ex A. Kerner (Ranunculaceae)

In the present paper we provide the first contribution to the knowledge of the flower-visiting insect assemblages of the alpine plant species Callianthemum kernerianum Freyn ex A. Kerner (Ranunculaceae). This focal plant species was selected since it is a steno-endemic and critically endangered species belonging to the IUCN red-list. Fifteen taxa were recorded, among which very few are true pollinators, whereas all the others can be considered only indirect pollinators. The peculiar phenology of the plant and the harsh habitat conditions in which it grows probably affect the richness and abundance of flower-visiting insects as well as of true pollinators. This could be the reason for this plant to be a self-compatible species.

Seasonal adaptations in energy budgeting in the primate Lepilemur leucopus.

The spiny forest of South Madagascar is one of the driest and most unpredictable habitats in Africa. The small-bodied, nocturnal primate Lepilemur leucopus lives in this harsh habitat with high diurnal and seasonal changes in ambient temperature. In this study, we investigated seasonal adaptions in energy budgeting of L. leucopus, which allow it to live under these conditions by measuring resting metabolic rate using open-flow respirometry. No signs of heterothermy were detected, and resting metabolic rate was significantly lower in the warmer wet season than in the colder dry season. In fact, L. leucopus possesses one of the lowest mass-specific metabolic rates measured so far for an endotherm, probably the result of adaptations to its habitat and folivorous and potentially toxic diet. Surprisingly, we identified a shift of the thermoneutral zone from between 25 and 30 °C in the wet season to between 29 and 32 °C in the cool dry season. L. leucopus seems to be more affected by the hot daytime temperatures during the dry season and thermoregulation seems to be more costly during this time, which makes this shift of the thermoneutral zone advantageous. Our findings suggest that L. leucopus has a very small scope to unfavorable conditions, making it highly vulnerable, e.g., to changing conditions due to climate change.

A betaine aldehyde dehydrogenase gene from Ammopiptanthus nanus enhances tolerance of Arabidopsis to high salt and drought stresses

Glycine betaine functions as an osmotic protectant in response of plant to abiotic stresses. In higher plants, the betaine aldehyde dehydrogenase (BADH) catalyzes the key step of glycine betaine biosynthesis. A lot of effort has been paid to cloning and heterologous expression of the BADH genes from different plants. However, different phenotypes were observed from the transgenic plants. Diversity of subcellular location and functions was found among the members of the BADH family. Our previous report described the cloning of an AnBADH gene from xerophyte Ammopiptanthus nanus and preliminary functional validation in Escherichia coli. In the present study, the function of the AnBADH gene for abiotic tolerance was further characterized by quantitative real time PCR and heterologous expression in Arabidopsis mutant. The results showed that the endogenous expression of the AnBADH gene was strongly induced by the treatments of high salt, dehydration, abscisic acid, heat, and cold. The heterologous expression of the AnBADH gene significantly enhanced tolerance of the Arabidopsis mutant to high salt and drought stresses. Under the stress conditions, the transgenic lines exhibited a more robust root system and a larger fresh weight, higher content of glycine betaine and proline, higher relative water content, lower relative electrolyte leakage and malondialdehyde content, compared to the untransformed mutant. These results suggest that the AnBADH gene encodes a functional betaine aldehyde dehydrogenase, and plays a critical role in the adaptation of A. nanus to its harsh habitat. It provides one more choice for genetic improvement of commercial crops for abiotic tolerance.

Using soil microbial inoculations to enhance substrate performance on extensive green roofs.

Green roofs are increasing in popularity in the urban environment for their contribution to green infrastructure; but their role for biodiversity is not often a design priority. Maximising biodiversity will impact positively on ecosystem services and is therefore fundamental for achieving the greatest benefits from green roofs. Extensive green roofs are lightweight systems generally constructed with a specialised growing medium that tends to be biologically limited and as such can be a harsh habitat for plants to thrive in. Thus, this investigation aimed to enhance the soil functioning with inoculations of soil microbes to increase plant diversity, improve vegetation health/performance and maximise access to soil nutrients. Manipulations included the addition of mycorrhizal fungi and a microbial mixture ('compost tea') to green roof rootzones, composed mainly of crushed brick or crushed concrete. The study revealed that growing media type and depth play a vital role in the microbial ecology of green roofs, with complex relationships between depth and type of substrate and the type of microbial inoculant applied, with no clear pattern being observed. For bait plant measurements (heights, leaf numbers, root/shoot biomass, leaf nutrients), a compost tea may have positive effects on plant performance when grown in substrates of shallower depths (5.5cm), even one year after inoculums are applied. Results from the species richness surveys show that diversity was significantly increased with the application of an AM fungal treatment and that overall, results suggest that brick-based substrate blends are most effective for vegetation performance as are deeper depths (although this varied with time). Microbial inoculations of green roof habitats appeared to be sustainable; they need only be done once for benefits to still been seen in subsequent years where treatments are added independently (not in combination). They seem to be a novel and viable method of enhancing rooftop conditions.

Diversity patterns of monocotiledonous geophytes in Mexico

Background: Geophytes, plants with underground perennating organs that lose their aerial organs annually, are able to survive in harsh habitats. This life form is common in the monocots that inhabit Mediterranean climates around the world. In Mexico only the northern area of Baja California has this type of climate.
 Hypothesis: In this study, we recorded the species and distribution of Mexican geophyte monocots to pinpoint diversity hotspots. Our hypothesis is that the highest diversity of geophytes will be found in biogeographic areas with complex topography and seasonal climate such like Trans-Mexican Volcanic Belt and Sierra Madre del Sur, not only in the north of the Baja California Peninsula.
 Data description: Records of geophytes were taken from different sources, collections, taxonomic references and diversity databases. Geophyte locations were mapped in the context of biogeographic and protected areas.
 Results: The Mexican geophyte flora is composed of 476 species, approximately 10% of the total diversity of monocots. Echeandia and Tigridia were the two most diverse genera. This flora is dominated by the taxa of Orchidaceae, Asparagaceae and Iridaceae, and nine small endemic genera were recorded. Geophyte diversity was highest in two biogeographic provinces: the Trans-Mexican Volcanic Belt and the Sierra Madre del Sur, in dry forests such as oak-pine, seasonally dry tropical forests and semi-arid shrubby vegetation.
 Conclusions: Diversity of geophytes in Mexico is similar compared with certain regions with Mediterranean climate around the world. Areas sustaining a high diversity and endemism of geophytes are located in the Mesoamerican Biodiversity Hotspot, in unprotected and threatened areas.

Gene Turnover Contributes to the Evolutionary Adaptation of Acidithiobacillus caldus: Insights from Comparative Genomics.

Acidithiobacillus caldus is an extremely acidophilic sulfur-oxidizer with specialized characteristics, such as tolerance to low pH and heavy metal resistance. To gain novel insights into its genetic complexity, we chosen six A. caldus strains for comparative survey. All strains analyzed in this study differ in geographic origins as well as in ecological preferences. Based on phylogenomic analysis, we clustered the six A. caldus strains isolated from various ecological niches into two groups: group 1 strains with smaller genomes and group 2 strains with larger genomes. We found no obvious intraspecific divergence with respect to predicted genes that are related to central metabolism and stress management strategies between these two groups. Although numerous highly homogeneous genes were observed, high genetic diversity was also detected. Preliminary inspection provided a first glimpse of the potential correlation between intraspecific diversity at the genome level and environmental variation, especially geochemical conditions. Evolutionary genetic analyses further showed evidence that the difference in environmental conditions might be a crucial factor to drive the divergent evolution of A. caldus species. We identified a diverse pool of mobile genetic elements including insertion sequences and genomic islands, which suggests a high frequency of genetic exchange in these harsh habitats. Comprehensive analysis revealed that gene gains and losses were both dominant evolutionary forces that directed the genomic diversification of A. caldus species. For instance, horizontal gene transfer and gene duplication events in group 2 strains might contribute to an increase in microbial DNA content and novel functions. Moreover, genomes undergo extensive changes in group 1 strains such as removal of potential non-functional DNA, which results in the formation of compact and streamlined genomes. Taken together, the findings presented herein show highly frequent gene turnover of A. caldus species that inhabit extremely acidic environments, and shed new light on the contribution of gene turnover to the evolutionary adaptation of acidophiles.

Transcriptomic responses of a simplified soil microcosm to a plant pathogen and its biocontrol agent reveal a complex reaction to harsh habitat.

BackgroundSoil microorganisms are key determinants of soil fertility and plant health. Soil phytopathogenic fungi are one of the most important causes of crop losses worldwide. Microbial biocontrol agents have been extensively studied as alternatives for controlling phytopathogenic soil microorganisms, but molecular interactions between them have mainly been characterised in dual cultures, without taking into account the soil microbial community. We used an RNA sequencing approach to elucidate the molecular interplay of a soil microbial community in response to a plant pathogen and its biocontrol agent, in order to examine the molecular patterns activated by the microorganisms.ResultsA simplified soil microcosm containing 11 soil microorganisms was incubated with a plant root pathogen (Armillaria mellea) and its biocontrol agent (Trichoderma atroviride) for 24 h under controlled conditions. More than 46 million paired-end reads were obtained for each replicate and 28,309 differentially expressed genes were identified in total. Pathway analysis revealed complex adaptations of soil microorganisms to the harsh conditions of the soil matrix and to reciprocal microbial competition/cooperation relationships. Both the phytopathogen and its biocontrol agent were specifically recognised by the simplified soil microcosm: defence reaction mechanisms and neutral adaptation processes were activated in response to competitive (T. atroviride) or non-competitive (A. mellea) microorganisms, respectively. Moreover, activation of resistance mechanisms dominated in the simplified soil microcosm in the presence of both A. mellea and T. atroviride. Biocontrol processes of T. atroviride were already activated during incubation in the simplified soil microcosm, possibly to occupy niches in a competitive ecosystem, and they were not further enhanced by the introduction of A. mellea.ConclusionsThis work represents an additional step towards understanding molecular interactions between plant pathogens and biocontrol agents within a soil ecosystem. Global transcriptional analysis of the simplified soil microcosm revealed complex metabolic adaptation in the soil environment and specific responses to antagonistic or neutral intruders.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-3174-4) contains supplementary material, which is available to authorized users.

Aboveground carbon stock, allocation and sequestration potential during vegetation recovery in the karst region of southwestern China: A case study at a watershed scale

Karst landscape in southwestern China is one of the most typical landscapes developed on carbonate bedrock and has the largest area in the world. Carbon sequestration potentials during secondary karst vegetation recovery remain uncertain. Based on the vegetation map and 87 sampling plots at five stages of natural vegetation succession, this study estimated aboveground (AG) vegetation carbon stocks and dynamics at a watershed scale. AG carbon density of grasslands, shrublands, shrub forests, secondary forests and primary forests was 1.70, 4.15, 22.3, 70.3, 142.2Mgha−1, respectively. The ten most important species stored 71.6–96.1% of total AG carbon stock, indicating that carbon pool in karst vegetation was determined by a few dominant species. Main contributors to AG carbon stock shifted from individuals in small diameter classes in shrublands to individuals in large diameter classes in primary forests, indicating that carbon increases in the early vegetation succession resulted from high recruitment of woody plants, while carbon accumulations in the later forests were mainly due to tree growth. The long time required for secondary forests to recover carbon density to the level of primary forests could be explained by the slow speed of large evergreen trees reaching a high level of dominance during secondary succession on the harsh habitats. The total AG carbon stock of the studied watershed (7.50×103ha) was 85.9×103 Mg, of which paddy fields, dry lands, grasslands, shrublands, shrub forests and secondary forests accounted for 22.6%, 3.49%, 0.34%, 5.97%, 12.3% and 55.3%, respectively. The AG carbon stock in this watershed would increase by 92.5% in 50–100 years and by 4.40 times in 140–200 years if the degraded vegetation types could continue to develop into mature forests. Although carbon density of karst forests was significantly lower than that of the forests on non-karst habitats in the same latitudinal zone, the degraded karst vegetation showed a great carbon sequestration potential due to the large distribution area in southwestern China.

Isolated trees with high crown coverage and densities increase pasture seed rain

Pasture and crop lands restrict seed dispersal near remnant forest fragments, especially by restricting the movements of dispersal agents and limiting propagule dispersal. Some factors can improve seed dispersal in open areas, such as the presence of high numbers of isolated trees in close proximity to forest fragments. We sought to determine if: (i) the structural characteristics and (ii) densities of isolated trees in pasture lands, and (iii) their distances from the forest fragments, influence seed dispersal. We installed 18 seed traps in each of six pastures (total=108 traps) bordering forest fragments distributed over 6 distance classes from the forest edges (0, 5, 10, 20, 40 and 80 m). We determined the characteristics of the plants surrounding the traps. GLM and GLMer analyses were performed and the best model was selected by AIC. We collected 8162 seeds (4722 anemochorous, 3304 epizoochorous, 72 autochorous, and 64 endozoochorous) belonging to 26 species. Our results showed that plants with high crown coverage close to forest fragments and at high densities in the pastures increased seed dispersal. These results may aid future restoration of pasture lands by improving seed dispersal in this harsh habitat and promoting better connectivity between forest fragments.

Dry-washes determine gene flow and genetic diversity in a common desert shrub

In deserts, many plant species exhibit a patchy spatial distribution within a harsh habitat matrix, where the likelihood of propagule dispersal among patches is uncertain, but may be promoted by landscape corridors or dispersal vectors. We examine the connectivity of a representative desert plant species (Acacia (Senegalia) greggii), and the ability of three major factors (animal dispersal agents, water flow along dry-washes, and climate) to facilitate dispersal within four watersheds in the Mojave National Preserve. We genotyped 323 individuals sampled across 22 one-hectare sites using ten nuclear microsatellite markers. A hierarchical AMOVA revealed no significant differentiation among watersheds (F RT = 0.00, P > 0.10), and very little genetic structure among all sites (F ST = 0.03, P 0.05), a distance measure based on rodent dispersal (P > 0.05), and a distance measure avoiding inhospitable climate (P > 0.05). An AIC comparison of generalized linear models found that within site genetic diversity (H E and allelic richness) and average relatedness were best explained by slope (which increases seed dispersal potential via water flow) and area of the upstream watershed (which determines the number of potential seed donors), rather than plant density or habitat suitability. Together, these findings indicate that dry-washes are key landscape features that enhance dispersal and regional connectivity in this patchy desert plant.

Metagenomic Signatures of Bacterial Adaptation to Life in the Phyllosphere of a Salt-Secreting Desert Tree.

The leaves of Tamarix aphylla, a globally distributed, salt-secreting desert tree, are dotted with alkaline droplets of high salinity. To successfully inhabit these organic carbon-rich droplets, bacteria need to be adapted to multiple stress factors, including high salinity, high alkalinity, high UV radiation, and periodic desiccation. To identify genes that are important for survival in this harsh habitat, microbial community DNA was extracted from the leaf surfaces of 10 Tamarix aphylla trees along a 350-km longitudinal gradient. Shotgun metagenomic sequencing, contig assembly, and binning yielded 17 genome bins, six of which were >80% complete. These genomic bins, representing three phyla (Proteobacteria,Bacteroidetes, and Firmicutes), were closely related to halophilic and alkaliphilic taxa isolated from aquatic and soil environments. Comparison of these genomic bins to the genomes of their closest relatives revealed functional traits characteristic of bacterial populations inhabiting the Tamarix phyllosphere, independent of their taxonomic affiliation. These functions, most notably light-sensing genes, are postulated to represent important adaptations toward colonization of this habitat. Plant leaves are an extensive and diverse microbial habitat, forming the main interface between solar energy and the terrestrial biosphere. There are hundreds of thousands of plant species in the world, exhibiting a wide range of morphologies, leaf surface chemistries, and ecological ranges. In order to understand the core adaptations of microorganisms to this habitat, it is important to diversify the type of leaves that are studied. This study provides an analysis of the genomic content of the most abundant bacterial inhabitants of the globally distributed, salt-secreting desert tree Tamarix aphylla Draft genomes of these bacteria were assembled, using the culture-independent technique of assembly and binning of metagenomic data. Analysis of the genomes reveals traits that are important for survival in this habitat, most notably, light-sensing and light utilization genes.

Harsh habitats? Waterfalls and their faunal dynamics in tropical Australia

There are few studies of the ecology of waterfalls despite their being prominent landscape features and of ecological interest because of their physical characteristics. We compared invertebrate assemblages of 5 waterfalls in the Australian Wet Tropics over 12–18 mo. Waterfall assemblages were distinct from those of riffles and bedrock, with some taxa particularly abundant on waterfalls (e.g. Simuliidae, Hydropsychidae) and others restricted to them (e.g. Blephariceridae, Pyralidae), and supported more species than bedrock but fewer than riffles. Differences among waterfalls related to differences in discharge, shade and habitat complexity. Waterfalls comprised a complex of microhabitat patches, with high-flow smooth, high-flow rough, vertical and spray zones most prevalent and distinguishable by gradient, roughness, water velocity, depth and invertebrate assemblages. In high-flow microhabitats rheophilic taxa (e.g. Simuliidae) were prevalent, while in the spray zone a range of madicolous taxa (e.g. various Coleoptera) occurred. Within microhabitats, temporal change was moderate, with stable composition over 12 months. Flood disturbance had limited effect on assemblages, as large flows overshot steep surfaces; drought may be more of a threat because recovery is hindered by isolation and lack of hyporheic refugia. Given their isolation, limited extent and distinctive fauna, waterfalls merit special conservation attention.

An La-related protein controls cell cycle arrest by nuclear retrograde transport of tRNAs during diapause formation in Artemia.

BackgroundIn eukaryotes, tRNA trafficking between the nucleus and cytoplasm is a complex process connected with cell cycle regulation. Such trafficking is therefore of fundamental importance in cell biology, and disruption of this process has grave consequences for cell viability and survival. To cope with harsh habitats, Artemia has evolved a special reproductive mode to release encysted embryos in which cell division can be maintained in a dormancy state for a long period.ResultsUsing Artemia as a peculiar model of the cell cycle, an La-related protein from Artemia, named Ar-Larp, was found to bind to tRNA and accumulate in the nucleus, leading to cell cycle arrest and controlling the onset of diapause formation in Artemia. Furthermore, exogenous gene expression of Ar-Larp could induce cell cycle arrest in cancer cells and suppress tumor growth in a xenograft mouse model, similar to the results obtained in diapause embryos of Artemia. Our study of tRNA trafficking indicated that Ar-Larp controls cell cycle arrest by binding to tRNAs and influencing their retrograde movement from the cytoplasm to the nucleus, which is connected to pathways involved in cell cycle checkpoints.ConclusionsThese findings in Artemia offer new insights into the mechanism underlying cell cycle arrest regulation, as well as providing a potentially novel approach to study tRNA retrograde movement from the cytoplasm to the nucleus.Electronic supplementary materialThe online version of this article (doi:10.1186/s12915-016-0239-4) contains supplementary material, which is available to authorized users.

Flight of Black-Necked Cranes (Grus nigricollis) with legs drawn up: behavioral responses to low temperature and duration of exposure

ABSTRACT Weather conditions considerably influence the behavior of wildlife, particularly those living in harsh habitats such as the plateau. In this study, we reported unusual flight behavior of Black-necked Cranes (Grus nigricollis) where legs are drawn up. Among 15 crane species, it is the only species that spends its entire life in alpine areas. Field observations were conducted during the three winters of 2006/07, 2009/10, and 2012/13 at Dashanbao National Nature Reserve (DNNR), northeastern Yunnan, China. At the population level, ~4% of Black-necked Cranes displayed this behavior, whereas a total of 156 individuals from 49 flocks displayed this behavior among the clearly observed 4,007 individuals of 751 crane flocks. Our results showed a strong negative correlation between prevalence of this behavior and departure temperature (r = −0.832, P = 0.005, n = 9). Moreover, the average temperature of the preceding 12 hrs and duration of exposure to subzero temperature had a significant effect on the...