Changes in the adult sex ratio of six duck species breeding populations over two decades

Despite all efforts,long-term changes in the adult sex ratios of breeding duck populations are still unclear;this uncertainty is especially true for male-bias populations,which are often under the scrutiny of researchers lacking convenient results for the active protection of endangered species.Species with male-bias populations are usually strongly affected by a decline in population size that leads to a higher extinction risk.In this study,we examined our long-term data of the abundance of breeding populations in six duck species(Mallard Anas platyrhynchos,Gadwall Mareca strepera,Red-crested Pochard Netta rufina,Common Pochard Aythya ferina,Tufted Duck Aythya fuligula,and Common Goldeneye Bucephala clangula)from fishponds in South Bohemia,Czechia,between 2004 and 2022.This evidence was used to assess long-term changes in the adult sex ratio in these breeding populations and investigate the possible effects of the NAO index(North Atlantic Oscillation index)on them,indicating climate conditions in winter.We determined a long-term decrease of the proportion of females in the breeding season in two of the six examined species:Common Pochard and Red-crested Pochard,which is driven by the long-term increase in the number of males in contrast to the decreasing or stable number of females likely caused by different migration behaviours between females and males.In the case of Common Pochard,in breeding populations,we estimated 60-65%of males in the early 2000s rising to 75-80%in the early 2020s.However,we establish no significant effects linked to climate conditions of the previous winter in these species as a crucial cause of the changes of the proportion of females in the breeding population.

Application of heat shock protein expression for detecting natural adaptation and exposure to stress in natural populations

Heat-shock proteins （HSPs） play an undisputed role for maintaining cellular functioning under environmental challenges and protein denaturing conditions. Compelling evidence points to an evolutionary important role of HSPs and a strict evolutionary control of these proteins as a balance between benefits and costs. While there is a great potential for using HSP expression for detecting natural adaptation and exposure to stress in natural populations, some obstacles and key issues await investigation. From an ecological perspective these key issues needs to be resolved in order to fully appreciate the complex responses and adaptations to stress and to increase our understanding of HSPs and other molecular chaperones for stress adaptation and potential use as biomarkers. Here, the current knowledge and understanding of HSPs is reviewed and a number of key issues including the interpretation of elevated HSP levels, the complications of extrapolating between laboratory and field conditions, the effects of choice of traits and methodology and the larger intra-and extracellular networks of interactions that HSPs participate in are discussed [Current Zoology 56 （6）： 703-713, 2010].

first record of sphenomorphus incognitus (thompson, 1912) (squamata:scincidae) from vietnam with some notes on natural history

Sphenomorphus incognitus is recorded for the first time outside of China. The new locality record is from the Tay Yen Tu Nature Reserve in Bac Giang Province, northeastern Vietnam at elevations between 200–450 m. Based on the newly collected specimens, we present an expanded description and provide data on the natural history of this species in northern Vietnam.

Distributional Data of the Lizard Fauna （Sauria） of the Maringa-Lopori-Wamba Landscape, Democratic Republic of the Congo

This paper presents the composition of the lizard fauna of Maringa-Lopori-Wamba landscape in the western portion of the central Congo basin in the Democratic Republic of the Congo and its weak similarity with the lizard fauna of Gaboon and Ituri faunal areas. It also fills a gap of knowledge in a region where no previous research on Sauria has been undertaken and signals the presence ofLeptosiaphos hylophilus and Lygodactylus n. sp. The paper mentions the finding of a subspecies of Gastropholis echinata. These data are important since collected for the first time in a spot where no herpetological research on lizards has previously been undertaken.

Evaluation of growth and reproduction as indicators of soil metal toxicity to the Collembolan, Sinella curviseta

Laboratory studies evaluated the sensitivity of Sinella curviseta Brook （Collembola： Entomobryidae） to selected heavy metals （Cu, Pb and Zn）. Survival, reproduction and growth of S. curviseta were determined in a 4-week exposure test in an agricultural soil amended with metals to concentrations of 100, 200, 400, 800, 1 600 and 3 200 mg/kg. Results showed reduction in adult survival and reproductive failure at the highest concentrations （3 200 mg/kg） of Cu and Zn. EC50reproduction values for Cu and Zn were approximately 442 and 2 760 mg/kg, respectively. Application of Pb at all levels resulted in large numbers of progeny and no significant mortality compared to controls. Adult growth rate decreased for all metal treatments compared to the controls, suggesting that metals affect S. curviseta metabolism and result in slower growth. We showed that reproduction is a slightly more sensitive parameter than growth. Since a growth test needs fewer juveniles and takes less time than a reproduction test, we conclude that the two parameters are complementary and could be used for a better ecotoxicological evaluation of contaminant levels. However, relative growth and reproduction sensitivities should be tested with more chemicals before a growth test is accepted as a faster sublethal test than a reproduction test.

The role of soil-borne fungi in driving the coexistence of Pinus massoniana and Lithocarpus glaber in a subtropical forest via plant-soil feedback

Aims Plant–soil feedback(PSF)is a key mechanism that can facilitate tree species coexistence and diversity.Substantial evidence suggests that species-specific soil-borne pathogens around adult trees limit the performance of home(conspecific)seedlings relative to foreign(heterospecific)seedlings.However,the underlying mechanism remains largely elusive.Methods Here,we conducted a reciprocal transplant pot experiment using seedlings and from two tree species,Pinus massoniana and Lithocarpus glaber that are dominant and coexist in a subtropical,evergreen,broad-leaf forest in Gutianshan,Zhejiang Province of eastern China.We examined how seedlings from the two tree species responded to soils originating from underneath their own versus the other tree species,using a full-factorial design.Additionally,we added a fungicide(benomyl)to half of the pots to evaluate the role of soil-borne fungi on seedling growth.Important Findings We found that the seedlings from L.glaber grew better in soils that were collected from beneath the canopy of P.massoniana,while seedling growth of P.massioniana was not affected by soil origin.The addition of fungicide benomyl resulted in a shift towards more positive PSF effects for L.glaber,indicating that L.glaber seedlings performed better in their own soils than in soils from P.massoniana in the absence of fungi.Our findings highlight the importance of soil-borne pathogenic and ectomycorrhizal fungi in driving PSF,and indicate that PSF may promote the coexistence of two subtropical tree species by reducing the performance of L.glaber in own soils.

Plant responses to variable timing of aboveground clipping and belowground herbivory depend on plant age

Aims Plants use different types of responses such as tolerance and induced defense to mitigate the effects of herbivores.The direc-tion and magnitude of both these plant responses can vary with plant age.However,most studies have focused on aboveground herbivory,whereas important feeding occurs belowground.Here,we tested the hypothesis that plant tolerance and defense following shoot damage or root herbivory depends on plant age.Methods In order to test our hypothesis,we exposed the perennial grass spe-cies Holcus lanatus to defoliation and root nematode inoculation at three growth stages(young,intermediate and old plants),and exam-ined responses of plant traits related to tolerance(regrowth follow-ing defoliation)and defense(leaf and root nitrogen and phenolics).Important Findings Defoliation overall reduced plant shoot and root biomass as well as foliar concentrations of phenolics regardless of plant age at defoli-ation.In contrast,defoliation increased foliar N concentrations,but only when defoliation occurred at intermediate and old plant age.Inoculation with root-feeding nematodes reduced root N concentra-tions after a prolonged period of growth,but only when nematodes had been inoculated when plants were young.The relative shoot re-growth rate of plants increased immediately after defoliation but this was independent of the plant age at which defoliation occurred,i.e.was not stronger in plants that were defoliated at a more advanced age,as hypothesized.Similarly,relative root growth rates increased shortly after defoliation,but this was only observed for plants defoli-ated when they were young.We conclude that plant responses to aboveground and belowground herbivory in traits related to both defense and tolerance are affected by plant age,but do not gener-ally change with plant age.

Does drought stress modify the effects of plant-growth promoting rhizobacteria on an aboveground chewing herbivore？

Soil microbes have important effects on the interactions of plants with their environment, by promoting plant growth, inducing resistance to pests or by conferring tolerance to abiotic stress. However, their effects are variable and the factors responsible for this variation are mainly unknown. Our aim was to assess how drought stress modifies the effect of the nonpathogenic rhizobacterium Pseudomonas simiae WCS417r on plant growth and resistance against the generalist leaf-chewing caterpillar Mamestra brassicae. We studied Arabidopsis tha/iana Col-0 plants, as well as mutants altered in the biosyn- thesis of the phytohormones jasmonic acid （JA） and abscisic acid （ABA）. Caterpillars did not prefer rhizobacteria-treated plants, independently of drought stress. Rhizobacteria colonization had a variable effect on caterpillar performance, which ranged from positive in one experiment to neutral in a second one. Drought had a consistent negative effect on herbivore performance; however, it did not modify the effect of rhizobacteria on herbivore performance. The effect of drought on herbivore performance was JA-mediated （confirmed with the use of the dde2-2 mutant）, but it was still present in the ABA-deficient mutant aba2-1. Plant biomass was reduced by both drought and herbivory but it was enhanced by rhizobacterial colonization. Pseudomonas simiae WCS417r is able to promote plant growth even when plants are suffering herbivory. Nevertheless, the microbial effect on the herbivore is variable, independently of drought stress. To get the best possible outcome from the rhizobacteria-plant mutualism it is important to understand which other factors may be responsible for its context-dependency.

Modeling the growth of individuals in crowded plant populations

Aims We present an improved model for the growth of individuals in plant populations experiencing competition.Methods Individuals grow sigmoidally according to the Birch model,which is similar to the more commonly used Richards model,but has the advantage that initial plant growth is always exponential.The individual plant growth models are coupled so that there is a maximum total biomass for the population.The effects of size-asymmetric competition are modeled with a parameter that reflects the size advantage that larger individual have over smaller individuals.We fit the model to data on individual growth in crowded populations of Chenopodium album.Important Findings When individual plant growth curves were not coupled,there was a negative or no correlation between initial growth rate and final size,suggesting that competitive interactions were more important in determining final plant size than were plants’initial growth rates.The coupled growth equations fit the data better than individual,uncoupled growth models,even though the number of estimated parameters in the coupled competitive growth model was far fewer,indicating the importance of modeling competition and the degree of size-asymmetric growth explicitly.A quantitative understanding of stand development in terms of the growth of individuals,as altered by competition,is within reach.

RESEARCH PROGRESS ON THE IMPACT OF NITROGEN DEPOSITION ON GLOBAL GRASSLANDS

Grasslands are globally-important ecosystems providing critical ecosystem services.The species composition and characteristics of grasslands vary considerably across the planet with a wide variety of different grasslands found.However,in many regions grasslands have been impacted by atmospheric nitrogen deposition originating from anthropogenic activities with effects on productivity,species composition and diversity widely reported.Impacts vary across grassland habitats but many show declines in species richness and increases in biomass production related to soil eutrophication and acidification.At a continental level,there is considerable variation in the research effort that has been put into understanding the impacts of nitrogen deposition.In Europe,North America and parts of Asia,although there are unanswered research questions,there is a good understanding of N deposition impacts in most grassland habitats.This is not the case in other regions with large knowledge gaps in some parts of the world.This paper reviews the impacts of N deposition on grasslands around the world,highlighting recent advances and areas where research is still needed.

Effects of plant-soil feedback on tree seedling growth under arid conditions

Plants are able to influence their growing environment by changing biotic and abiotic soil conditions.These soil conditions in turn can influence plant growth conditions,which is called plant–soil feedback.Plant–soil feedback is known to be operative in a wide variety of ecosystems ranging from temperate grasslands to tropical rain forests.However,little is known about how it operates in arid environments.We examined the role of plant–soil feedbacks on tree seedling growth in relation to water availability as occurring in arid ecosystems along the west coast of South America.Methods In a two-phased greenhouse experiment,we compared plant–soil feedback effects under three water levels(no water,10%gravimetric moisture and 15%gravimetric moisture).We used sterilized soil inoculated with soil collected from northwest Peru(Prosopis pallida forests)and from two sites in north-central Chile(Prosopis chilensis forest and scrublands without P.chilensis).Important Findings Plant–soil feedbacks differed between plant species and soil origins,but water availability did not influence the feedback effects.Plant–soil feedbacks differed in direction and strength in the three soil origins studied.Plant–soil feedbacks of plants grown in Peruvian forest soil were negative for leaf biomass and positive for root length.In contrast,feedbacks were neutral for plants growing in Chilean scrubland soil and positive for leaf biomass for those growing in Chilean forest soil.Our results show that under arid conditions,effects of plant–soil feedback depend upon context.Moreover,the results suggest that plant–soil feedback can influence trade-offs between root growth and leaf biomass investment and as such that feedback interactions between plants and soil biota can make plants either more tolerant or vulnerable to droughts.Based on dissecting plant–soil feedbacks into aboveground and belowground tissue responses,we conclude that plant–soil feedback can enhance plant colonization in some arid ecosystems by promoting root growth.

The promises and challenges of research on plant-insect-microbe interactions

Ecological interactions are of paramount importance for the functioning and health of ecosystems. Phytophagous insects are part of complex ecological networks involving abiotic factors, host plants, natural enemies, and benefi- cial organisms （McLean et al., 2016）. Insects and plants are also associated durably or transitorily with a wealth of microbes including pathogens, commensals and beneficial partners from a vast array of microbial taxa （Sugio et al., 2015）. In recent years, evidence has accumulated that microbes directly or indirectly influence plant-insect interactions at individual, population and community levels.

Effect of host-cocoon mass on adult size in the secondary hyperparasitoid wasp, Pteromalus semotus （Hymenoptera： Pteromalidae）

Parasitoids have long proven to be model organisms in studying resourcerelated constraints on immature development. Here we examine the relationship between host cocoon （= pupal） size in the gregarious endoparasitoid wasp, Cotesia glomerata, and development time and adult size in the solitary idiobiont hyperparasitoid, Pteromalus semotus. Little is known about the biology or ecology of this ecto-hyperparasitoid species, although it is one of the major secondary hyperparasitoids of C. glomerata. The size of the adult wasp covaried with the size of the host cocoon at parasitism. Moreover, female wasps were larger than male wasps for a given cocoon size. Adult wasps have remarkably long life-spans, 3 months on average. Longevity did not significantly differ with sex. We also examined how larvae of P. semotus exclude other potential competitors. P. semotus is protandrous, with females taking significantly longer to complete their development than males. In experiments where several eggs of P. semotus were placed on individual pupae of C. glomerata, newly hatched hyperparasitoid larvae moved rapidly over the surface of the host and destroyed the eggs of any conspecifics by biting them before they would initiate feeding on host tissues. Our results are discussed in relation to those with other studies with solitary ichneumonid idiobiont hyperparasitoids of C. glomerata.

Growth substrates alter aboveground plant microbial and metabolic properties thereby influencing insect herbivore performance

The gut microbiome of plant-eaters is affected by the food they eat,but it is currently unclear how the plant metabolome and microbiome are influenced by the substrate the plant grows in and how this subsequently impacts the feeding behavior and gut microbiomes of insect herbivores.Here,we use Plutella xylostella caterpillars and show that the larvae prefer leaves of cabbage plants growing in a vermiculite substrate to those from plants growing in conventional soil systems.From a plant metabolomics analysis,we identified 20 plant metabolites that were related to caterpillar feeding performance.In a bioassay,the effects of these plant metabolites on insects'feeding were tested.Nitrate and compounds enriched with leaves of soilless cultivation promoted the feeding of insects,while compounds enriched with leaves of plants growing in natural soil decreased feeding.Several microbial groups(e.g.,Sporolactobacillus,Haliangium)detected inside the plant correlated with caterpillar feeding performance and other microbial groups,such as Ramlibacter and Methylophilus,correlated with the gut microbiome.Our results highlight the role of growth substrates on the food metabolome and microbiome and on the feeding performance and the gut microbiome of plant feeders.It illustrates how belowground factors can influence the aboveground properties of plant-animal systems,which has important implications for plant growth and pest control.