Population genetic differentiation and phenotypic plasticity of Ambrosia artemisiifolia under different nitrogen levels.

Rapid adaptive evolution and phenotypic plasticity are two mechanisms that often underlie invasiveness of alien plant species, but whether they can co-occur within invasive plant populations under altered environmental conditions such as nitrogen (N) enrichment has seldom been explored. Latitudinal clines in plant trait responses to variation in environmental factors may provide evidence of local adaptation. Here, we inferred the relative contributions of phenotypic plasticity and local adaptation to the performance of the invasive plant Ambrosia artemisiifolia under different soil N levels, using a common garden approach. We grew A. artemisiifolia individuals raised from seeds that were sampled from six invasive populations along a wide latitudinal cline in China (23°42' N to 45°43' N) under three N (0, 5, and 10 g N m-2 ) levels in a common garden. Results show significant interpopulation genetic differentiation in plant height, number of branches, total biomass, and transpiration rate of the invader A. artemisiifolia across the N treatments. The populations also expressed genetic differentiation in basal diameter, growth rate, leaf area, seed width, root biomass, aboveground biomass, stomatal conductance, and intercellular CO2 concentration regardless of N treatments. Moreover, plants from different populations of the invader displayed plastic responses in time to first flower, hundred-grain weight, net photosynthetic rate, and relative biomass allocation to roots and shoots and seed length under different N treatments. Additionally, individuals of A. artemisiifolia from higher latitudes grew shorter and allocated less biomass to the roots regardless of N treatment, while latitudinal cline (or lack thereof) in other traits depended on the level of N in which the plants were grown. Overall, these results suggest that rapid adaptive evolution and phenotypic plasticity in the various traits that we quantified may jointly contribute to invasiveness of A. artemisiifolia under different levels of N availability. More broadly, the results support the idea that phenotypic plasticity and rapid adaptive evolution can jointly enable invasive plants to colonize a wide range of environmental conditions.

Herbivory and elevated levels of CO2 and nutrients separately, rather than synergistically, impacted biomass production and allocation in invasive and native plant species.

Large parts of the Earth are experiencing environmental change caused by alien plant invasions, rising atmospheric concentration of carbon dioxide (CO2 ), and nutrient enrichments. Elevated CO2 and nutrient concentrations can separately favour growth of invasive plants over that of natives but how herbivory may modulate the magnitude and direction of net responses by the two groups of plants to simultaneous CO2 and nutrient enrichments remains unknown. In line with the enemy release hypothesis, invasive plant species should reallocate metabolites from costly anti-herbivore defences into greater growth following escape from intense herbivory in the native range. Therefore, invasive plants should have greater growth than native plants under simultaneous CO2 and nutrient enrichments in the absence of herbivory. To test this prediction, we grew nine congeneric pairs of invasive and native plant species that naturally co-occurred in grasslands in China under two levels each of nutrient enrichment (low-nutrient vs. high-nutrient), herbivory (with herbivory vs. without herbivory) and under ambient (412.9 ± 0.6 ppm) and elevated (790.1 ± 6.2 ppm) levels of CO2 concentrations in open top chambers in a common garden. Elevated CO2 and nutrient enrichment separately increased total plant biomass, while herbivory reduced it regardless of the plant invasive status. High-nutrient treatment caused the plants to allocate a significantly lower proportion of total biomass to roots, while herbivory induced an opposite pattern. Herbivory suppressed total biomass production more strongly in native plants than invasive plants. The plants exhibited significant interspecific and intergeneric variation in their responses to the various treatment combinations. Overall, these results suggest that elevated CO2 and nutrients and herbivory may separately, rather than synergistically, impact productivity of the invasive and co-occurring native plant species in our study system. Moreover, interspecific variation in resource-use strategies was more important than invasive status in determining plant responses to the various treatment combinations.

Directional and stabilizing selection shaped morphological, reproductive, and physiological traits of the invader Solidago canadensis.

Trait evolution in invasive plant species is important because it can impact demographic parameters key to invasion success. Invasive plant species often show phenotypic clines along geographic and climatic gradients. However, the relative contributions of natural selection and neutral evolutionary processes to phenotypic trait variation among populations of invasive plants remain unclear. A common method to assess whether a trait has been shaped by natural selection or neutral evolutionary processes is to compare the geographical pattern for the trait of interest to the divergence in neutral genetic loci (i.e., Q ST -F ST comparisons). Subsequently, a redundancy analysis (RDA) can facilitate identification of putative agents of natural selection on the trait. Here, we employed both a Q ST -F ST comparisons approach and RDA to infer whether natural selection shaped traits of invasive populations of Solidago canadensis in China and identify the potential environmental drivers of natural selection. We addressed two questions: (1) Did natural selection drive phenotypic trait variation among S. canadensis populations? (2) Did climatic, latitudinal, longitudinal, and altitudinal gradients drive patterns of genetic variation among S. canadensis populations? We found significant directional selection for several morphological and reproductive traits (i.e., Q ST > F ST) and stabilizing selection for physiological traits (i.e., Q ST < F ST). The RDA showed that stem biomass of S. canadensis was strongly positively correlated with longitude, while leaf width ratio and specific leaf area were significantly positively correlated with the mean diurnal range. Stem biomass had a strong negative correlation with annual precipitation. Moreover, height of S. canadensis individuals was strongly positively correlated with altitude and precipitation of the wettest quarter. A longitudinal shift in precipitation seasonality likely selected for larger stem biomass in S. canadensis. Overall, these results suggest that longitudinal and altitudinal clines in climate exerted strong selection pressures that shaped the phenotypic traits of S. canadensis.

Distribution of upper limit of the prescriptive zone values for acclimatized and unacclimatized individuals.

Heat stress has an adverse impact on worker health and well-being, and the effects will increase with more frequent and severe heat events associated with global warming. Acclimatization to heat stress is widely considered to be a critical mitigation strategy and wet bulb globe temperature- (WBGT-) based occupational standards and guidelines contain adjustments for acclimatization. The purpose here was to 1) compare the mean values for the upper limit of the prescriptive zone (ULPZ, below which the rise in core temperature is minimal) between unacclimatized and acclimatized men and women; 2) demonstrate that the change in the occupational exposure limit (ΔOEL) due to acclimatization is independent of metabolic rate; 3) examine the relation between ΔOEL and body surface area (BSA); and 4) compare the exposure-response curves between unacclimatized and acclimatized populations. Empirically derived ULPZ data for unacclimatized participants from Pennsylvania State University (PSU) and acclimatized participants from University of South Florida (USF) were used to explore the difference between unacclimatized and acclimatized heat exposure limits. The findings provide support for a constant 3°C WBGT OEL decrease to account for unacclimatized workers. Body surface area explained part of the difference in ULPZ values between men and women. In addition, the pooled PSU and USF data provide insight into the distribution of individual values for the ULPZ among young, healthy unacclimatized and acclimatized populations in support of occupational heat stress guidelines.NEW & NOTEWORTHY Occupational exposure limit guidelines using wet bulb globe temperature (WBGT) distinguish between acclimatized and unacclimatized workers with about a 3°C difference between them. For the first time, empirical data from two laboratories provide support for acclimatization state adjustments. Using a constant difference rather than increasing differences with metabolic rate better describes the limit for unacclimatized participants. Furthermore, the lower upper limit of the prescriptive zone (ULPZ) values set forth for women do not relate to fitness level but are partly explained by their smaller body surface area (BSA). An examination of individual ULPZ values suggests that many unacclimatized individuals should be able to sustain safe work at the exposure limit for acclimatized workers.

Livelihood Diversification and Residents' Welfare: Evidence from Maasai Mara National Reserve.

The contradiction between environmental protection and livelihood development is becoming increasingly serious for most protected areas in developing countries. Livelihood diversification is an efficient way to increase household income to alleviate poverty related to environmental protection. However, its impacts on household welfare in protected areas have rarely been quantitatively explored. This article investigates the determinants of four livelihood strategies in the Maasai Mara National Reserve and explores the association between livelihood diversification and household income and its heterogeneities. Based on the sustainable livelihoods framework and the information collected from 409 households through face-to-face interviews, this study adopted multivariate regression models to obtain consistent results. Results show that the determinants of the four strategies differed. Natural capital, physical capital, and financial capital had significant associations with the probability of adopting the strategy of livestock breeding. Physical capital, financial capital, human capital, and social capital were associated with the probability of adopting the joint strategy of livestock breeding and crop planting and the joint strategy of livestock breeding and off-farm activities. The probability of adopting the joint strategy of livestock breeding, crop planting, and off-farm activities was associated with all five kinds of livelihood capital except for financial capital. Diversification strategies, especially those involving off-farm activities, played greater roles in raising household income. The findings indicate that the government and management authority of Maasai Mara National Reserve should provide the households around the protected area with more off-farm employment opportunities to increase the welfare of local residents as well as to utilize natural resources appropriately, especially for those located far away from the protected area.

Nutrient enrichment promotes invasion success of alien plants via increased growth and suppression of chemical defenses.

In support of the prediction of the enemy release hypothesis regarding a growth-defense trade-off, invasive alien plants often exhibit greater growth and lower anti-herbivory defenses than native plants. However, it remains unclear how nutrient enrichment of invaded habitats may influence competitive interactions between invasive alien and co-occurring native plants, as well as production of anti-herbivore defense compounds, growth-promoting hormones, and defense-regulating hormones by the two groups of plants. Here, we tested whether: (i) nutrient enrichment causes invasive alien plants to produce greater biomass and lower concentrations of the defense compounds flavonoids and tannins than native plants; and (ii) invasive alien plants produce lower concentrations of a defense-regulating hormone jasmonic acid (JA) and higher concentrations of a growth-promoting hormone gibberellic acid (GA3). In a greenhouse experiment, we grew five congeneric pairs of invasive alien and native plant species under two levels each of nutrient enrichment (low vs. high), simulated herbivory (leaf clipping vs. no-clipping), and competition (alone vs. competition) in 2.5-L pots. In the absence of competition, high-nutrient treatment induced a greater increase in total biomass of invasive alien species than that of native species, whereas the reverse was true under competition as native species benefitted more from nutrient enrichment than invasive alien species. Moreover, high-nutrient treatment caused a greater increase in total biomass of invasive alien species than that of native species in the presence of simulated herbivory. Competition induced higher production of flavonoids and tannins. Simulated herbivory induced higher flavonoid expression in invasive alien plants under low-nutrient than high-nutrient treatments. However, flavonoid concentrations of native plants did not change under nutrient enrichment and simulated herbivory treatments. Invasive alien plants produced higher concentrations of GA3 than native plants. Taken together, these results suggest that impact of nutrient enrichment on growth of invasive alien and co-occurring native plants may depend on the level of competition that they experience. Moreover, invasive alien plants might adjust their flavonoid-based defense more efficiently than native plants in response to variation in soil nutrient availability and herbivory pressure. Our findings suggest that large-scale efforts to reduce nutrient enrichment of invaded habitats may help to control future invasiveness of target alien plant species.

Opposite effects of nutrient enrichment and an invasive snail on the growth of invasive and native macrophytes.

Many ecosystems are now co-invaded by alien plant and herbivore species. The evolutionary naivety of native plants to alien herbivores can make the plants more susceptible to the detrimental effects of herbivory than co-occurring invasive plants, in accordance with the apparent competition hypothesis. Moreover, the invasional meltdown hypothesis predicts that in multiply invaded ecosystems, invasive species can facilitate each other's impacts on native communities. Although there is growing empirical support for these hypotheses, facilitative interactions between invasive plants and herbivores remain underexplored in aquatic ecosystems. Many freshwater ecosystems are co-invaded by aquatic macrophytes and mollusks and simultaneously experience nutrient enrichment. However, the interactive effects of these ecological processes on native macrophyte communities remain an underexplored area. To test these effects, we performed a freshwater mesocosm experiment in which we grew a synthetic native community of three macrophyte species under two levels of invasion by an alien macrophyte Myriophyllum aquaticum (invasion vs. no invasion) and fully crossed with two levels of nutrient enrichment (enrichment vs. no enrichment) and herbivory by an invasive snail Pomacea canaliculata (herbivory vs. no herbivory). In line with the invasional meltdown and apparent competition hypotheses, we found that the proportional aboveground biomass yield of the invasive macrophyte, relative to that of the native macrophyte community, was significantly greater in the presence of the invasive herbivore. Evidence of a reciprocal facilitative effect of the invasive macrophyte on the invasive herbivore is provided by results showing that the herbivore produced greater egg biomass in the presence versus in the absence of M. aquaticum. However, nutrient enrichment reduced the mean proportional aboveground biomass yield of the invasive macrophyte. Our results suggested that herbivory by invader P. canaliculata may enhance the invasiveness of M. aquaticum. However, nutrient enrichment of habitats that already harbor M. aquaticum may slow down the invasive spread of the macrophyte. Broadly, our study underscores the significance of considering several factors and their interactions when assessing the impact of invasive species, especially considering that many habitats experience co-invasion by plants and herbivores and simultaneously undergo various other disturbances, including nutrient enrichment.

Invasive plant species that experience lower herbivory pressure may evolve lower diversities of chemical defense compounds in the exotic range.

PREMISE: Invasive plant species often escape from specialist herbivores and are more likely to be attacked by generalist herbivores in the exotic range. Consequently, the shifting defense hypothesis predicts that invasive plants will produce higher concentrations of qualitative defense compounds to deter dominant generalist herbivores in the exotic range. Here, I additionally propose a reduced chemical diversity hypothesis (RCDH), which predicts that reduced herbivory pressure will select for invasive plant genotypes that produce lower diversities of chemical defense compounds in the exotic range. METHODS: I tested whether (1) invasive Brassica nigra populations express a lower diversity and an overall higher concentration of glucosinolate compounds than native-range B. nigra; (2) Brassica nigra individuals that express high diversities and concentrations of glucosinolate compounds are more attractive to specialist and deterrent to generalist herbivores; and (3) tissues of invasive B. nigra are less palatable than tissues of native-range B. nigra to the generalist herbivores Theba pisana and Helix aspersa. RESULTS: Invasive B. nigra populations produced a significantly lower diversity of glucosinolate compounds, a marginally higher concentration of total glucosinolates, and a significantly higher concentration of sinigrin (the dominant glucosinolate). Leaf tissues of invasive B. nigra were significantly less palatable to T. pisana and marginally less so to H. aspersa. Brassica nigra individuals that expressed high concentrations of total glucosinolate compounds were visited by a low diversity of generalist herbivore species in the field. CONCLUSIONS: In line with the RCDH, the lower diversity of glucosinolate compounds produced by invasive B. nigra populations likely resulted from selection imposed by reduced herbivory pressure in the exotic range.

Older populations of the invader Solidago canadensis exhibit stronger positive plant-soil feedbacks and competitive ability in China.

PREMISE: The enemy release hypothesis predicts that release from natural enemies, including soil-borne pathogens, liberates invasive plants from a negative regulating force. Nevertheless, invasive plants may acquire novel enemies and mutualists in the introduced range, which may cause variable effects on invader growth. However, how soil microorganisms may influence competitive ability of invasive plants along invasion chronosequences has been little explored. METHODS: Using the invasive plant Solidago canadensis, we tested whether longer residence times are associated with stronger negative plant-soil feedbacks and thus weaker competitive abilities at the individual level. We grew S. canadensis individuals from 36 populations with different residence times across southeastern China in competition versus no competition and in three different types of soils: (1) conspecific rhizospheric soils; (2) soils from uninvaded patches; and (3) sterilized soil. For our competitor treatments, we constructed synthetic communities of four native species (Bidens parviflora, Solanum nigrum, Kalimeris indica, and Mosla scabra), which naturally co-occur with Solidago canadensis in the field. RESULTS: Solidago canadensis populations with longer residence times experienced stronger positive plant-soil feedbacks and had greater competitive responses (i.e., produced greater above-ground biomass and grew taller) in conspecific rhizospheric soils than in sterilized or uninvaded soils. Moreover, S. canadensis from older populations significantly suppressed above-ground biomass of the native communities in rhizospheric and uninvaded soils but not in sterilized soil. CONCLUSIONS: The present results suggest that older populations of S. canadensis experience stronger positive plant-soil feedbacks, which may enhance their competitive ability against native plant communities.

Brain charts for the human lifespan.

Over the past few decades, neuroimaging has become a ubiquitous tool in basic research and clinical studies of the human brain. However, no reference standards currently exist to quantify individual differences in neuroimaging metrics over time, in contrast to growth charts for anthropometric traits such as height and weight1. Here we assemble an interactive open resource to benchmark brain morphology derived from any current or future sample of MRI data ( http://www.brainchart.io/ ). With the goal of basing these reference charts on the largest and most inclusive dataset available, acknowledging limitations due to known biases of MRI studies relative to the diversity of the global population, we aggregated 123,984 MRI scans, across more than 100 primary studies, from 101,457 human participants between 115 days post-conception to 100 years of age. MRI metrics were quantified by centile scores, relative to non-linear trajectories2 of brain structural changes, and rates of change, over the lifespan. Brain charts identified previously unreported neurodevelopmental milestones3, showed high stability of individuals across longitudinal assessments, and demonstrated robustness to technical and methodological differences between primary studies. Centile scores showed increased heritability compared with non-centiled MRI phenotypes, and provided a standardized measure of atypical brain structure that revealed patterns of neuroanatomical variation across neurological and psychiatric disorders. In summary, brain charts are an essential step towards robust quantification of individual variation benchmarked to normative trajectories in multiple, commonly used neuroimaging phenotypes.

Native plant species show evolutionary responses to invasion by Parthenium hysterophorus in an African savanna.

Invasive plant species often competitively displace native plant species but some populations of native plant species can evolve adaptation to competition from invasive plants and persist in invaded habitats. However, studies are lacking that examine how variation in abiotic conditions in invaded landscapes may affect fitness of native plants that have adapted to compete with invasive plants. I tested whether invasion by Parthenium hysterophorus in Nairobi National Park - Kenya may have selected for native plant individuals with greater competitive ability than conspecific naïve natives in nutrient-rich and mesic soil conditions. I compared vegetative growth and seed yields of invader-experienced and conspecific naïve individuals of seven native species. Invader-experienced natives grew shorter than naïve natives regardless of growth conditions. Nevertheless, the two groups of native plants also exhibited treatment-specific differences in competitive ability against P. hysterophorus. Invader-experienced natives displayed plasticity in seed yield under drought treatment, while naïve natives did not. Moreover, drought treatment enhanced competitive effects of invader-experienced natives on P. hysterophorus, while nutrient enrichment relaxed competitive effects of invader-experienced natives on the invader. The results suggest that P. hysterophorus may have selected for shorter native plant genotypes that also exhibit plasticity in competitive ability under drought conditions.

A comparative study on the influence of third point of reference on condylar guidance settings in a semi-adjustable articulator with lateral cephalographs: An in-vivo study.

AIM: The study aimed to evaluate the effect on condylar guidance values with casts mounted by facebow transfer (Guichet's point as the third point of reference), Bonwill's, and radiographic method. MATERIALS AND METHODS: The dentulous subject's casts were mounted to a semi-adjustable articulator (Artex Type AR) after facebow transfer with Guichet's point as the third point of reference and also by Bonwill's method. Protrusive records made earlier were utilized to program the right and left side condylar guidance value. Two digital lateral cephalograms were made, one in centric relation, and one in protrusion and the condyles were traced and overlapped. The condylar guidance readings obtained by Bonwill's method, facebow transfer, and lateral cephalometric tracings were compared in this study using the SPSS (Version 17.0 Illinois, Chicago, USA) software. RESULTS: The condylar guidance values obtained from Bonwill's and the facebow transfer method (p < 0.001) was lesser than the radiographic method. The values obtained by casts mounted to the Bonwill's method differed significantly (p < 0.001) from the other two methods. CONCLUSION: The values obtained by facebow transfer were closer to the radiographic values whereas the values obtained by Bonwill's method mounting differed markedly.

A multi-centre, cross-sectional study on coronavirus disease 2019 in Bangladesh: clinical epidemiology and short-term outcomes in recovered individuals.

Coronavirus disease 2019 (COVID-19) rapidly became a global pandemic. This study aimed to investigate severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) -associated epidemiology and clinical outcomes in Bangladesh in order to understand the future course of the COVID-19 pandemic and develop approaches to prevention. A cross-sectional study based on retrospective interviews was conducted on 1021 individuals with RT-PCR-confirmed COVID-19 admitted in six different hospitals in Bangladesh and who recovered 4 weeks before the interview date. Of the 1021 patients, 111 (10.9%) were asymptomatic and the other 910 (89.1%) were symptomatic. Higher prevalence of COVID-19 was found in the male population (75%), in cohorts with B-positive blood group (36.3%) and in the 31-40 years age group. Common symptoms observed in our study participants were fever (72.4%), cough (55.9%), loss of taste (40.7%) and body ache (40%); whereas among the biochemical parameters, neutrophil count (46.4%), D-dimer (46.1%) and ferritin (37.9%) levels were elevated. Among the recovered individuals, short-term outcomes including pains and aches (31.8%), weakened attention span (24.4%) and anxiety or depression (23.1%) were also significantly prevalent in the symptomatic cases with comorbidities. Our study showed that in Bangladesh, adult males aged between 31 and 40 years were more vulnerable to developing COVID-19. It also indicated a rising trend of asymptomatic cases as the pandemic progressed. As a consequence, deployment of interventions to curb further spread of community infection is necessary to avoid grave outcomes of COVID-19 in Bangladesh.

Allelopathic effects of native and invasive Brassica nigra do not support the novel-weapons hypothesis.

PREMISE: The novel-weapons hypothesis predicts that some plants are successful invaders because they release allelopathic compounds that are highly suppressive to naïve competitors in invaded ranges but are relatively ineffective against competitors in the native range. For its part, the evolution of enhanced weaponry hypothesis predicts that invasive populations may evolve increased expression of the allelopathic compounds. However, these predictions have rarely been tested empirically. METHODS: Here, we made aqueous extracts of roots and shoots of invasive (North American) and native (European) Brassica nigra plants. Seeds of nine species from North America and nine species from Europe were exposed to these extracts. As control solutions, we used pure distilled water and distilled water with the osmotic potential adjusted with polyethylene glycol (PEG) to match that of root and shoot extracts of B. nigra. RESULTS: The extracts had a strong negative effect on germination rates and seedling root lengths of target species compared to the water-control. Compared to the osmolality-adjusted controls, the extracts had a negative effect on seedling root length. We found no differences between the effects of B. nigra plant extracts from the invasive vs. native populations on germination rates and seedling root growth of target plant species. Responses were largely independent of whether the target plant species were from the invaded or native range of B. nigra. CONCLUSIONS: The results show that B. nigra can interfere with other species through allelochemical interactions, but do not support predictions of the novel-weapons hypothesis and evolution of increased allelopathy.

Can polyploidy confer invasive plants with a wider climatic tolerance? A test using Solidago canadensis.

Polyploidy can cause variation in plant functional traits and thereby generate individuals that can adapt to fluctuating environments and exploit new environments. However, few empirical studies have tested for an association between ploidy level and climatic tolerance of invasive cytotypes relative to conspecific native-range cytotypes. Here, we used an invasive plant Solidago canadensis to test whether invasive populations had a higher proportion of polyploids, greater height and stem-base diameter, and occupied a wider range of climatic conditions than conspecific native-range populations. We also tested whether the invasive populations had overcome genetic founder effects. We sampled a total of 80 populations in parts of the invaded range in China and native range in North America for in situ measurements of plant height and stem-base diameter in the field and for population genetic and cytotype analyses. To examine climatic correlates, we augmented our field-sampled data with occurrence records obtained from Global Biodiversity Information Facility. All, except one, of the populations that we sampled in China occurred in a humid subtropical climate. In contrast, the North American populations occurred in humid continental, humid subtropical, and semi-arid climatic zones. All populations of S. canadensis in China were purely hexaploid, while the North American populations were diploid, tetraploid, and hexaploid. The invasive hexaploids were significantly taller and had a larger stem-base diameter than native hexaploids. Native hexaploids were significantly taller and had larger stem-base diameter than native diploids. Climatic correlate assessment found that invasive and native populations occupied different climatic envelopes, with invasive populations occurring in warmer and less seasonal climates than native populations. However, there was no significant correlation between ploidy level and climatic envelope of S. canadensis. Molecular phylogeography data suggest reduced genetic founder effects in the invaded range. Overall, these results suggest that polyploidy does not influence S. canadensis climatic tolerance.

The invasive plant Solidago canadensis exhibits partial local adaptation to low salinity at germination but not at later life-history stages.

PREMISE: Evolutionary adaptation may enable plants to inhabit a broad range of environments. However, germination and early life-history stages have seldom been considered in estimates of evolutionary adaptation. Moreover, whether soil microbial communities can influence evolutionary adaptation in plants remains little explored. METHODS: We used reciprocal transplant experiments to investigate whether two populations of an invasive plant Solidago canadensis that occur in contrasting habitats of low versus high salinity expressed adaptation to the respective salinity levels. We germinated S. canadensis seeds collected from low-and high-salinity habitats under low- and high-salt treatments. We also raised S. canadensis seedlings from the two salinity habitats under low- and high-salt treatments and in the presence versus absence of microbial communities from the two habitats. RESULTS: Genotypes from a low-salinity habitat had higher germination rates under low-salt treatment than genotypes from a high-salinity habitat. However, both genotypes had similar germination rates under a high-salt treatment. The two genotypes also had similar seedling survival and biomass responses to low- and high-salt treatments. Nevertheless, seedling biomass was significantly higher under low salt treatment. Soil microbial communities did not influence biomass of S. canadensis under the two salt treatments. CONCLUSIONS: The results on germination rates suggest partial local adaptation to low salinity. However, there was no evidence of local adaptation to salinity at the seedling survival and growth stages. The finding that germination and seedling biomass responded to different salt treatments suggests that the two traits are important for salt tolerance.

Livelihood impacts and governance processes of community-based wildlife conservation in Maasai Mara ecosystem, Kenya.

Community-based wildlife conservation (CBWC) programmes have been a pervasive paradigm in the conservation circles since the 1970s. The key elements of such programmes are that local communities are given ownership rights or custodianship and management responsibilities over wildlife, and that they gain social and economic benefits from conservation of the resources. However, to date, there have been only a few studies that offer in-depth analyses of the interplay between governance processes and livelihood impacts of CBWC programmes. Here, I conducted key informant interviews and focus group discussions in five wildlife conservancies in the Maasai Mara ecosystem in Kenya to address the following questions: i) What are the perceived impacts of the wildlife conservancies on livelihoods of the local people? ii) To what extent are the wildlife conservancies governed in relation to the principles of environmental governance? I assessed impacts on livelihoods by applying the Sustainable Livelihoods Framework to explore perceived conservancy-related benefits and costs (i.e. perceived changes in social, financial, human, physical, and natural capitals). I assessed governance by asking the respondents whether the following eight principles of environmental governance were applied: legitimacy, transparency, accountability, inclusiveness, fairness, integration, capability, and adaptability. Perceived benefits of participating in wildlife co-management were identified as: enhanced income from gainful employment and new business opportunities, membership to cooperative societies and participation in community work (e.g. school bursary and feeding programmes), enhanced social relations, improved access to credit and health facilities, enhanced physical infrastructure (schools, roads and bridges), improved physical security and coordinated sharing of provisioning ecosystem services like pasture and water. The principles of legitimacy, inclusiveness, and integration had reportedly been well implemented in wildlife co-management. However, the institutional mechanisms for sharing resources within the conservancies lacked transparency, accountability, and fairness, and tended to favour those who were politically connected to the leadership of the conservancies. Moreover, most of the conservancies had weak systems and few resources to facilitate delivery on responsibilities (i.e. had low capability), and had some costs associated with human-wildlife conflicts. For an improved co-management of wildlife to be achieved in these conservancies, local institutions should be reconfigured to allow active participation by conservancy landowners in decision-making, information sharing, and equitable access to conservancy-related benefits.

Thermally stratified flow of Jeffrey fluid with homogeneous-heterogeneous reactions and non-Fourier heat flux model.

This article investigates the mixed convective flow of Jeffrey fluid near the axisymmetric stagnation point over an inclined permeable stretching cylinder. Analysis subjected to Cattaneo-Christov heat flux, thermal stratification and homogeneous-heterogeneous reactions are accounted. Suitable transformations are employed to obtain nonlinear ordinary differential system. Non-dimensional system is computed by Homotopy technique. Graphs and tables are constructed to analyze the influence of different flow parameters on temperature, concentration and velocity fields. The interpretation of skin friction coefficient is deliberated. It is noticed from obtained results that temperature is a decreasing function of thermal stratification parameter. Reverse behaviour of concentration is witnessed for higher estimations of homogeneous and heterogeneous parameters. Numerical results are compared with previous published results and found to be in good agreement for special casesof the emerging parameters.

A native parasitic plant and soil microorganisms facilitate a native plant co-occurrence with an invasive plant.

Invasive plants often interact with antagonists that include native parasitic plants and pathogenic soil microbes, which may reduce fitness of the invaders. However, to date, most of the studies on the ecological consequences of antagonistic interactions between invasive plants and the resident biota focused only on pairwise interactions. A full understanding of invasion dynamics requires studies that test the effects of multiple antagonists on fitness of invasive plants and co-occurring native plants. Here, we used an invasive plant Mikania micrantha, a co-occurring native plant Coix lacryma-jobi, and a native holoparasitic plant Cuscuta campestris to test whether parasitism on M. micrantha interacts with soil fungi and bacteria to reduce fitness of the invader and promote growth of the co-occurring native plant. In a factorial setup, M. micrantha and C. lacryma-jobi were grown together in pots in the presence versus absence of parasitism on M. micrantha by C. campestris and in the presence versus absence of full complements of soil bacteria and fungi. Fungicide and bactericide were used to suppress soil fungi and bacteria, respectively. Findings show that heavy parasitism by C. campestris caused the greatest reduction in M. micrantha biomass when soil fungi and bacteria were suppressed. In contrast, the co-occurring native plant C. lacryma-jobi experienced the greatest increase in biomass when grown with heavily parasitized M. micrantha and in the presence of a full complement of soil fungi and bacteria. Taken together, our results suggest that selective parasitism on susceptible invasive plants by native parasitic plants and soil microorganisms may diminish competitive ability of invasive plants and facilitate native plant coexistence with invasive plants.