Effect of Environmental Stress on the Nutrient Stoichiometry of the Clonal Plant Phragmites australis in Inland Riparian Wetlands of Northwest China

Clonal plants play an important role in determining ecosystem properties such as community stability, species diversity and nutrient cycling. However, relatively little information is available about the stoichiometric characteristics of clonal plants and their drivers in inland riparian wetlands under strong environmental stress. In this manuscript, we studied the clonal plant Phragmites australis in an inland riparian wetland of Northwest China and compared its nutrient distribution and stoichiometry trade-offs as well as its responses to soil environmental factors in three different environments, namely, a wetland, a salt marsh, and a desert. We found that (1) P. australis could adapt to heterogeneous environments by changing its nutrient allocation strategies, as evidenced by the significant decrease in N and P concentrations, and significant increase in whole-plant C:P and N:P ratios from the wetland to the desert habitats. (2) P. australis adapted to stressful environments by changing its nutrient allocation patterns among different modules, showing a greater tendency to invest N and P in underground modules (rhizomes and roots) and an increase in the utilization efficiency of N and P in the leaves, and stems as environmental stress increased. (3) The C-N, C-P, and N:P-C in the whole plant and in each module showed significant anisotropic growth relationships in the three habitats (P < 0.05). (4) Soil water, pH and salt were the main factors limiting nutrient stoichiometry. The results of this study clarified the ecological adaptation mechanism of the clonal plant P. australis to heterogeneous environments and provided targeted protection strategies for inland riparian wetlands in Northwest China.

When your host shuts down: larval diapause impacts host-microbiome interactions in Nasonia vitripennis

BackgroundThe life cycles of many insect species include an obligatory or facultative diapause stage with arrested development and low metabolic activity as an overwintering strategy. Diapause is characterised by profound physiological changes in endocrine activity, cell proliferation and nutrient metabolism. However, little is known regarding host-microbiome interactions during diapause, despite the importance of bacterial symbionts for host nutrition and development. In this work, we investigated (i) the role of the microbiome for host nutrient allocation during diapause and (ii) the impact of larval diapause on microbiome dynamics in the parasitoid waspNasonia vitripennis, a model organism for host-microbiome interactions.ResultsOur results demonstrate that the microbiome is essential for host nutrient allocation during diapause inN. vitripennis, as axenic diapausing larvae had consistently lower glucose and glycerol levels than conventional diapausing larvae, especially when exposed to cold temperature. In turn, microbiome composition was altered in diapausing larvae, potentially due to changes in the surrounding temperature, host nutrient levels and a downregulation of host immune genes. Importantly, prolonged larval diapause had a transstadial effect on the adult microbiome, with unknown consequences for host fitness. Notably, the most dominant microbiome member,Providenciasp., was drastically reduced in adults after more than 4 months of larval diapause, while potential bacterial pathogens increased in abundance.ConclusionThis work investigates host-microbiome interactions during a crucial developmental stage, which challenges both the insect host and its microbial associates. The impact of diapause on the microbiome is likely due to several factors, including altered host regulatory mechanisms and changes in the host environment.

Metabolic Cost of a Nutritional Symbiont Manifests in Delayed Reproduction in a Grain Pest Beetle

Animals engage in a plethora of mutualistic interactions with microorganisms that can confer various benefits to their host but can also incur context-dependent costs. The sawtoothed grain beetle Oryzaephilus surinamensis harbors nutritional, intracellular Bacteroidetes bacteria that supplement precursors for the cuticle synthesis and thereby enhance desiccation resistance of its host. Experimental elimination of the symbiont impairs cuticle formation and reduces fitness under desiccation stress but does not disrupt the host’s life cycle. For this study, we first demonstrated that symbiont populations showed the strongest growth at the end of metamorphosis and then declined continuously in males, but not in females. The symbiont loss neither impacted the development time until adulthood nor adult mortality or lifespan. Furthermore, lifetime reproduction was not influenced by the symbiont presence. However, symbiotic females started to reproduce almost two weeks later than aposymbiotic ones. Thus, symbiont presence incurs a metabolic and context-dependent fitness cost to females, probably due to a nutrient allocation trade-off between symbiont growth and sexual maturation. The O. surinamensis symbiosis thereby represents an experimentally amenable system to study eco-evolutionary dynamics under variable selection pressures.

Phenotypic flexibility and drought avoidance in taro (Colocasia esculenta (L.) Schott)

Taro (Colocasia esculenta (L.) Schott) is a substantial staple food in most of the tropical regions. Prolonged exposure to drought impairs crop production worldwide. Tolerant crops have the best capability to cope and avoid drought, through phenotypic flexibility mechanisms. The water use efficiency (WUE) is well known in taro crops, but very scarce information is available relating to their nutrient efficiency (NER) in drought conditions. Our work provided pertinent information about the physiological variation of seven taro accessions subjected to seven months of drought, by recording the differences for nutrient allocation, chlorophyll canopy, biomass loss, and stress intensity. Significant relationships between control and drought treatments on WUE (+85%), total plant biomass (TPB, -26.8%), chlorophyll content index (CCI, +1.8%), and nutrient harvest index (NHI, +0.2%) were detected. Drought led to a generalized loss of TPB as drought avoidance strategy, although distinct phenotypic flexibility was observed through the root:shoot ratio (R:S) and stress index (SI) from the corm and shoot organs. The nutrient allocation from the corms to shoots, with NER increase registered in drought conditions, can be a valuable tool to complement the TPB and WUE productivity traits, to be used in taro breeding programs.