1. Chain formation is common feature among non-motile marine phytoplankton. Several theories exist around the potential benefits of larger colonies. 2. Here we test the hypothesis that predation is one of the evolutionary drivers behind chain formation and chain length plasticity. We exposed cultures of Thalassiosira rotula, Chaetoceros curvisetus and Chaetoceros affinis to copepodamides, a chemical alarm signal from copepods. This was coupled with a grazing experiment which compared grazing rates on different chain lengths. 3. Our results show that T. rotula and C. curvisetus decreased their chain lengths by 79 % and 49 %, respectively, in response to copepodamides. Single cells and short chains were grazed at lower rates and the copepodamide driven size shift led to 30 % and 12 % lower grazing in T. rotula and C. curvisetus respectively. C. affinis did not respond to copepodamides and did not show the same size dependent clearance rate. 4. We found that more chain forming diatoms respond to predatory cues from copepods than previously known, and that predation is likely an important driver in the evolution of colony size and colony size plasticity.

Evolutionary theory predicts that infection by a parasite that reduces future host survival or fecundity should select for increased investment in current reproduction. In this study we use the cestode Ligula intestinalis and its intermediate fish host Engraulicypris sardella in Wissman Bay, Lake Nyasa (Tanzania) as a model system. Using data about infection of E. sardella fish hosts by L. intestinalis collected for a period of 10 years, we explored whether parasite infection affects the fecundity of the fish host E. sardella, and whether host reproductive investment has increased at the expense of somatic growth. We found that L. intestinalis had a strong negative effect on the fecundity of its intermediate fish host. For the non-infected fish we observed an increase in relative gonadal weight at maturity over the study period, while size at maturity decreased. These findings suggest that the life history of E. sardella has been shifting towards earlier reproduction. Further studies are warranted to assess whether these changes reflect plastic or evolutionary responses. We also discuss the interaction between parasite and fishery-mediated selection as a possible explanation for the decline of E. sardella stock in the lake. KEYWORDS Life history evolution; African Great Lakes; Lake Nyasa; Usipa; Lake Malawi sardine; Parasite invasion; Environmental change.

In the present study, to the evaluate genetic diversity and genetic structure of a mutational rice (B810S) with a color marker from China, the entire sequence of the atpH gene of the chloroplast genome from B810S was amplified by polymerase chain reaction (PCR). The PCR products were sequenced, and sequence variations in the atpH gene were then examined. The entire sequence of the atpH gene was 245 bp in size. Compared it with 810S, whichis the male parent of B810S, the results showed a similarity of 51.22%. There are 2 haplotypes in their atpH gene sequences and the haplotype diversity and nucleotide diversity were 1.0000 and 0.41250, respectively. In addition, phylogenetic analysis of B810S and other normal rice strains was conducted and a phylogenetic tree was constructedusing maximum likelihood (ML) method based on the atpH gene sequence from the chloroplast genome. The results of phylogenetic analysis showed that B810S separated from other rice strains formed an independent branch in the phylogenetic tree, which suggests that B810S with a color marker is a new male sterile rice line. The molecular approach employed in this study provides a foundation for further study of the genetic diversity and structure of rices in different geographical regions of China and other regions in the world.

The capacity and extent to which prey species forage is often dependent on the temporal and/or spatial distribution of predators. Predation risk within a given habitat may differ according to the structure of the landscape and ecological community. Predators may frequent selected habitat patches and it is these areas prey are expected to avoid. Aside from the direct removal of prey individuals through predation, the density of prey populations may be altered as a result of a perceived predator presence and the energetically expensive responses initiated. A predator presence may be perceived upon the detection of sensory environmental cues, including a predator’s pheromones. The Landscape of Fear (LOF) concept proposes the exposure to a real or perceived predation threat may disrupt prey distribution and activity. Such an environment may be referred to as a ‘landscape of fear’, though the interspecies complexes and abiotic factors affecting a predator-prey relationship should not be omitted when quantifying the effects of predation. Here, we summarise the initial and more recent publications addressing the LOF theory, identifying known aspects and potential for future research.

Aim: The current geographic distribution of plants and their dispersers are a result of coevolution, but the reciprocity effects on the distribution of large seed pine and primary seed dispersers required understanding of (a) the distribution range and distribution characteristics of each species, and (b) the overlapping of distribution areas of animals and plants to explore whether they match. Location: China Methods: To find the target species, we identified eight large-seeded pine species in China in terms of seed size and wing traits as well as four primary seed disperser species in terms of body size, diet and food storage behavior. To map the geographical distribution, we obtained species distribution information from books, literature and GBIF. We then analyzed the distribution relationship by overlapping the distribution areas and patterns comprehensively. Results: We identified eight species of large-seeded pines (Pinus fenzeliana, P. gerardiana, P. dabeshanensis, P. koraiensis, P. pumila, P. bungeana, P. armandii, and P. sibirica) and four species of primary seed dispersers (Nucifraga caryocatactes, Sciurus vulgaris, Tamias sibiricus, and Sciurotamias davidianus). Pines interlaced from the Northeast to the Southwest of China along the mountains with an average altitude of 1000-2000 m, while each species of seed disperser had a wide distribution range that overlapped completely or partially with that of four or more species of the large-seeded pines. For pines that lack sufficient research on seed dispersal, our research provides them with potential seed dispersers Main conclusions: The distribution pattern of large-seeded pines and the primary seed dispersers was matched, we believed that reciprocal relationship promotes this distribution pattern. Our study highlights the importance of incorporating the ecological consequences of geographical distribution into reciprocal interactions between species and biodiversity conservation.

Summary 1. Research has indicated that increases in nitrogen (N) deposition can greatly affect ecosystem processes and functions. There is limited information about the effects of long-term N addition on soil nematodes and their functional composition, although nematodes are the most abundant multicellular animals on Earth. 2. We conducted a field experiment in 2004 with four levels of N addition (0, 60, 120, and 240 kg N ha-1 yr-1) in a subtropical Cunninghamia lanceolata forest. Soil samples with three depths (0-20, 20-40 and 40-60 cm) were collected and the community structure, diversity and trophic groups of soil nematodes were determined in 2014. 3. N addition significantly increased the abundance of bacterial- and fungal-feeding nematodes, but decreased the abundance of plant-feeding nematodes at the 0-20 cm soil layer. Accordingly, the plant parasite index and enrichment index decreased but the basal index and channel index increased, which weaken the importance of the plant-based energy channel, but enhance the importance of the fungal-based energy channel. N addition had no effects on the diversity of soil nematodes in three soil depths. Structural equation modeling analysis indicated that N loading directly changed plant-feeding (total r2=0.42) nematodes, or indirectly affected bacterial- (r2=0.43), fungal- (r2=0.31) and plant-feeding nematodes via change soil nutrients, soil water content and pH. 4. These findings suggest that N addition can change the community structure and energy channels soil nematodes, which would affect soil processes and food web functions in forest soils under future environmental change scenarios.

Alpine wetlands play a sensitive function in global carbon cycle during the ongoing climate warming, yet the temporal patterns of carbon dynamics from in situ ground-based long-term observations remains unclear. Here, we analyzed the continuous net ecosystem CO2 exchange (NEE) measured with the eddy covariance technique over an alpine peatland on the northeastern Qinghai-Tibetan Plateau from 2007 to 2016. The wetland acted as a net CO2 source with a positive NEE (120.4 ± 34.8 gCm-2year-1, Mean ± S.D.), with the mean annual gross primary productivity (GPP) of 500.3 ± 59.4 gCm-2year-1 and annual ecosystem respiration (RES) of 620.7 ± 74.2 gCm-2year-1. At the seasonal scale, the classification and regression trees (CART) analysis showed that aggregated growing season degree days (GDD) was the predominant determinant on variations in monthly NEE and monthly GPP. Variations in monthly RES were determined by soil temperature (Ts). Furthermore, non-growing season Ts had a significant positive correlation with the following year annual GPP (p<0.05). Non-growing season RES only accounted for about 25% of annual RES, but had significant correlation with annual RES and annual NEE (p<0.05). The further partial correlation analysis showed that non-growing season air temperature (Ta, p = 0.05), rather than precipitation (PPT, p = 0.25) was a predominant determinant on variations in annual NEE. Our results highlighted the importance in carbon dynamics of climate fluctuations and CO2 emission from the non-growing season in alpine wetlands. We speculated that the vast peadlands would positively feedback to climate change on the Tibetan plateau where the non-growing season warming was significant.

Ambrosia artemisiifolia and Ambrosia trifida are two species of very harmful and invasive plants of the same genus. However, it remains unclear why A. artemisiifolia is more widely distributed than A. trifida worldwide. Distribution and abundance of these two species were surveyed and measured from 2010 to 2017 in the Yili Valley, Xinjiang, China. Soil temperature and humidity, main companion species, the biological characteristics in farmland ecotone, residential area, roadside and grassland, and water demand of the two species were determined and studied from 2017 to 2018. The area occupied by A. artemisiifolia in the Yili Valley was more extensive than that of A. trifida, while the abundance of A. artemisiifolia in grassland was less than that of A. trifida at eight years after invasion. The interspecific competitive ability of two species were stronger than those of companion species in farmland ecotone, residential, and roadside. In addition, A. trifida had greater interspecific competitive ability than other plant species in grassland. The seed size and seed weight of A. trifida were five times or eight times those of A.artemisiifolia. When comparing the changes under simulated annual precipitation of 840 mm versus 280 mm, the seed yield per m2 of A. trifida decreased from 50,185 to 19, while that of A. artemisiifolia decreased from 15,579 to 530. The differences in the distribution of the two species are mainly due to differences in interspecific competitive ability, seed size, and water dependence. The two species have stronger interspecific competitive ability than that of companion species, but A. artemisiifolia has a smaller seed size and stronger drought tolerance, which allows A. artemisiifolia to spread farther than A. trifida. The reason for wider distribution of A. trifida in grassland is that A. trifida has stronger interspecific competitive ability than A. artemisiifolia under sufficient water.

Plasticity in salt tolerance can be crucial for successful biological invasions of novel habitats by marine gastropods. The intertidal snail Batillaria attramentaria, which is native to East Asia but invaded the western shores of North America from Japan eighty years ago, provides an opportunity to examine how environmental salinity may shape behavioral and morphological traits. In this study, we compared the movement distance of four B. attramentaria populations from native (Korea and Japan) and introduced (USA) habitats under various salinity levels (13, 23, 33, and 43 PSU) during 30 days of exposure in the lab. We sequenced a partial mitochondrial CO1 gene to infer phylogenetic relationships among populations and confirmed two divergent mitochondrial lineages constituting our sample sets. Using a statistic model-selection approach, we investigated the effects of geographic distribution and genetic composition on locomotor performance in response to salt stress. Snails exposed to acute low salinity (13 PSU) reduced their locomotion and were unable to perform at their normal level (the moving pace of snails exposed to 33 PSU). We did not detect any meaningful differences in locomotor response to salt stress between the two genetic lineages or between the native snails (Japan versus Korea populations), but we found significant locomotor differences between the native and introduced groups (Japan or Korea versus the USA). We suggest that the greater magnitude of tidal salinity fluctuation at the USA location may have influenced locomotor responses to salt stress in introduced snails.

1 Extreme events such as extreme drought and rainfall are predicted to be more frequent under ongoing climate change. Biomass allocation is an important strategy for plants to respond to such changes. However, few studies explored the effects of water availability on biomass allocation of dominant plants in Inner Mongolia steppe in China. 2 A controlled experiment was conducted by treating four perennial plant species (Leymus chinensis, Stipa grandis, Artemisia frigida and Potentilla acaulis) with eight levels of water availability, which was selected based on the local annual mean precipitation, simulating rainfall scenarios facing climate change. 3 Water availability significantly affected the aboveground biomass, belowground biomass, total biomass and the ratio of belowground biomass and aboveground biomass of plants, and these effects were modified by species. Our results indicated that plants could modify their biomass allocation strategies to adapt to the gradient of water availability. 4 Climatic factors such as precipitation and temperature always co-vary, thus responses of plants to more complicated climate change (e.g. the joint variation of temperature and rainfall) should be further explored in order to better understand grassland management and restoration under climate change.

Foliar water uptake (FWU) may be a significant way for trees to obtain water; however, studies are lacking on FWU. To determine whether FWU occurs in Platycladus orientalis growing in seasonally arid areas, the process of FWU under soil water content (SWC) of 3.9–6.5%, 6.5–9.1%, 9.1–15.6%, 15.6–20.8%, and 20.8–26.0% and different precipitation gradients (1/mm, 5 mm/h, 10 mm/h, and 15 mm/h) was studied using precipitation with labeled isotopes in simulated rainfall experiments with indoor potted plants. The results showed that FWU occurred in each treatment if the SWC ≤ 21.9% no matter the amount of precipitation. The absorption rate of rainfall by leaves increased with the increase of rainfall intensity, but decreased with the increase of SWC. The greatest rates of FWU were 2.77% and 9.52% of rainfall intensity of 1 mm/h and 15 mm/h, respectively, in the 3.9–6.5% treatment. The precipitation absorbed by the leaves of P. orientalis can be transported to xylem or root system along the water potential gradient of leaves–branches–roots. The precipitation with reverse migration in branches and roots increased with the increase of the water potential gradient of leaves–branches–roots. This study provided insight into water use patterns and water migration within trees.

1.Large carnivore conservation is complex and remains a massive challenge across the world. Owing to their wide-ranging habits, large carnivores encounter various anthropogenic pressures which may potentially lead to conflict. Animal movement is linked with individual fitness as it is important for various biological processes. Therefore, studying how large carnivores adapt their movement to dynamic landscape conditions is vital for management and conservation policy. 2.We first quantified the movement parameters of four large carnivores in and outside protected-areas in India (tiger, leopard, dhole and wolf). We then tested the effects of human pressures like human density, road density and land use types on the movement of the species. Finally, we examined the configuration of core areas as a strategy to exploit human-dominated landscape. 3.Our findings suggest that the mean hourly displacement of 4 large carnivores differed across habitats. Mean displacement of large carnivores varied from 77.58m/h for leopards to 665.3m/h for wolves. Tigers outside PAs exhibited higher displacement as compared to tigers inside PAs. Displacement during day and night were significantly different for tigers inside and outside PAs (P=0.03), and wolf whereas no difference was found for leopard and dholes. The movement and ranging patterns of species outside PAs were influenced by anthropogenic factors such as human population, road network density, and landuse. All carnivores showed multiple areas of intensive use or cores in their home ranges. The range of the core area sizes was greater for species outside PAs (tiger and wolf) in human-altered landscapes. 4.Movement ecology of large carnivores has not been explored using such an exhaustive dataset in India. Our study attempts to extend theoretical concepts to applied management problems. This study can be a starting point for rigorous studies on interlinking animal movement and landscape management for large carnivore conservation and policy-making in the Anthropocene.

The reliability of evolutionary reconstructions based on the fossil record critically depends on our knowledge of the factors affecting the fossilization of soft-bodied organisms. Despite considerable research effort, these factors are still poorly understood. The extreme rarity of unicellular non-skeletal eukaryotic fossils compared to multicellular ones is an example of a pattern that apparently requires taphonomic explanation. In order to elucidate the main prerequisites for the preservation of soft-bodied organisms, we conducted long-term (1-5 years) taphonomic experiments with the model crustacean Artemia salina buried in five different sediments. The subsequent analysis of the carcasses and sediments revealed that, in our experimental settings, better preservation was associated with the fast deposition of aluminium and silicon on organic tissues. Other elements such as calcium, magnesium and iron, which can also accumulate quickly on the carcasses, appear to be much less efficient in preventing decay. Next, we asked if the carcasses of uni- and multicellular organisms differ in their ability to accumulate aluminium ions on their surface. The experiments with the flagellate Euglena gracilis and the sponge Spongilla lacustris showed that aluminium ions are more readily deposited onto a multicellular body. This was further confirmed by the experiments with uni- and multicellular stages of the social amoeba Dictyostelium discoideum. The results lead us to speculate that the evolution of cell adhesion molecules, which provide efficient cell-cell and cell-substrate binding, probably can explain the rich fossil record of multicellular soft-bodied organisms, the poor fossil record of non-skeletal unicellular eukaryotes, and the explosive emergence of the Cambrian diversity of soft bodied fossils.

Resource quality can have direct or indirect effects on female oviposition choice, offspring growth and survival, and ultimately on body size and sex ratio. We examined these patterns in Sirex noctilio Fabricus, the globally invasive European pine woodwasp, in South African Pinus patula plantations. We studied how tree position as well as natural variation in biotic and abiotic factors influenced sex-specific density, larval size, tunnel length, male proportion, and survival across development. Twenty infested trees divided into top, middle, and bottom sections were sampled at three time points during larval development. We measured moisture content, bluestain fungal colonization, and co-occurring insect density and counted, measured, and sexed all immature wasps. A subset of larval tunnels was measured to assess tunnel length and resource use efficiency (tunnel length as a function of immature wasp size).  Wasp density increased from the bottoms to the tops of trees for both males and females. However, the largest individuals and the longest tunnels were found in bottom sections. Male bias was strong (~10:1) and likewise differed among sections, with the highest proportion in the middle and top sections. Sex ratios became more strongly male biased due to high female mortality, especially in top and middle sections. Biotic and abiotic factors such as colonization by Diplodia sapinea, weevil (Pissodes sp.) density, and wood moisture explained modest residual variation in our primary mixed effects models (0-22%). These findings contribute to a more comprehensive understanding of sex-specific resource quality for S. noctilio and of how variation in key biotic and abiotic factors can influence body size, sex ratio, and survival in this economically important woodwasp.

Phytolith-occluded carbon (PhytOC) is an important long-term stable carbon fraction in grassland ecosystems, and plays a promising role in global carbon sequestration. Determination of the PhytOC traits of different plants in major grassland types is crucial for precisely assessing their PhytOC sequestration potential. Precipitation is the predominant factor in controlling net primary productivity (NPP) and species composition of the semiarid steppe grasslands. We selected three representative steppe communities of desert steppe, dry typical steppe and wet typical steppe in Northern Grasslands of China along a precipitation gradient, to investigate their species composition, biomass production and PhytOC content for quantifying its long-term carbon sequestration potential. Our results showed that (i) the phytolith and PhytOC contents in plants differed significantly among species, with dominant grass and sedge species having relatively high contents, and the contents are significantly higher in below- than the aboveground parts. (ii) The phytolith contents of plant communities were 16.68, 17.94 and 15.85 g kg-1 in the above- and 85.44, 58.73 and 76.94 g kg-1 in the belowground biomass of desert steppe, dry typical steppe and wet typical steppe, respectively; and the PhytOC contents were 0.68, 0.48 and 0.59 g kg-1 in the above- and 1.11, 0.72 and 1.02 g kg-1 in the belowground biomass of the three steppe types. (iii) Climatic factors affected phytolith and PhytOC production of steppe communities mainly through altering plant production, whereas their effects on phytolith and PhytOC contents were relatively small. Plant aboveground biomass and PhytOC content were strongly associated with the current-year climate and soil bio-available Si content; while plant belowground biomass and PhytOC content were relatively stable, and their variation across the sites is in accordance with the spatial variation in the long-term means of climatic and soil factors, reflecting the perenniality of plant belowground part.

The desert harvester ant Veromessor pergandei displays geographic variation in colony founding with queens initiating nests singly (haplometrosis) or in groups (pleometrosis). The transition from haplo- to pleometroic founding is associated with lower rainfall. Numerous hypotheses have been proposed to explain the evolution of cooperative founding in this species, but the ultimate explanation remains unanswered. In laboratory experiments, water level was positively associated with survival, condition, and brood production by single queens. Queen survival also was positively influenced by water level and queen number in a two-factor experiment. Water level also was a significant effect for three measures of queen condition, but queen number was not significant for any measure. Foundress queens excavated after two weeks of desiccating conditions were dehydrated compared to alate queens captured from their natal colony, indicating that desiccation can be a source of queen mortality. Long-term monitoring in central Arizona, USA, documented that recruitment only occurred in 4 of 20 years. A discriminant analysis using rainfall as a predictor of recruitment correctly predicted recruitment in 17 of 20 years for total rainfall from January–June (the period for mating flights and establishment) and in 19 of 20 years for early plus late rainfall (January–March and April–June, respectively), often with a posterior probability > 0.90. Moreover, recruitment occurred only in years in which both early and late rainfall exceeded the long-term mean. This result also was supported by the discriminant analysis predicting no recruitment when long-term mean early and late rainfall were included as ungrouped periods. These data suggest that pleometrosis in V. pergandei evolved to enhance colony survival in areas with harsh abiotic (desiccating) conditions, facilitating colonization of habitats in which solitary queens could not establish even in wet years. This favorable-year hypothesis supports enhanced worker production as the primary advantage of pleometrosis.

Body mass is often viewed as a proxy of past access to resources and of future survival and reproductive success. Links between body mass and survival or reproduction are, however, likely to differ between age classes and sexes. Remarkably, this is rarely taken into account in selection analyses. Selection on body mass is likely to be the primary target accounting for juvenile survival until reproduction but may weaken after recruitment. Males and females also often differ in how they use resources for reproduction and survival. Using a long-term study on yellow-bellied marmots (Marmota flaviventer), we show that body mass was under stabilizing selection in the first years of life, before recruitment, which changed to positive directional selection as age increased and animals matured. We found no evidence that selection across age-classes on body mass differed between sexes. By investigating the link between running speed and body mass, we show that the capacity to escape predators was not consistent across age classes and followed a quadratic relationship at young ages only. Overall, our results indicate that mature age classes exhibit traditional patterns of positive selection on body mass, as expected in a hibernating mammal, but that mass in the first years of life is subject to stabilizing selection which may come from additional predation pressures that negate the benefits of the largest body masses. Our study highlights the importance to disentangle selection pressures on traits across critical age (or life) classes.

1. Ongoing intensification and fragmentation of European agricultural landscapes dramatically reduce biodiversity and associated functions. To sustain ecosystem services such as ant mediated pest control, the enhancement of perennial non-crop areas holds great potential. 2. To study the potential of newly established grasslands to enhance ant diversity and associated functions, we used hand collection data to investigate differences in ant community composition (a) between cereal crops, old grasslands, and new grassland transects of three years age; (b) depending on ant functional traits; and linked to (c) natural pest control services quantified through predation experiments. 3. Ant species richness did not significantly differ between new and old grasslands, but was significantly higher in grasslands compared to cereal crops. Contrary, ant community composition of new grasslands was more similar to cereal crops and distinct from the species-pool of old grasslands. The functional trait space covered by the ant communities overlapped between old and new grasslands but was extended in the old grasslands. Pest control did not differ significantly between habitat types, and therefore could not be linked to the prevalence of functional traits related to biocontrol services in new grasslands. 4. Our findings show trends of convergence between old and new grasslands, but also indicate that enhancing ant diversity through newly established grasslands takes longer than three years to provide comparable biodiversity and functions. 5. Synthesis and applications Newly established grasslands can increase ant species richness, abundance, and pest control in agroecosystems. However, three years after establishment, new grasslands were still dominated by common agrobiont ant species and lacked habitat specialists present in old grasslands, who require a constant supply of food resources and long colonization times. New grasslands represent a promising measure for enhancing agricultural landscapes but must be preserved in the longer term to sustain biodiversity and associated ecosystem services.

Huanglongbing (HLB) is the most devastating citrus disease worldwide. The causal organism of the disease is spread by an insect vector, Diaphorina citri, commonly known as Asian citrus psyllid (ACP). Current management of HLB relies either on physical removal of the infected plants or on chemical control of ACP. Both methods are not overly effective and costly. In addition, public concerns regarding insecticide residues in fruit have greatly increased in recent years. It has been hypothesized that plant volatiles could act as repellents to ACP, thus reduce the incidence of HLB. To test this hypothesis, the repellency of fresh tissues of 41 aromatic plant species to ACP was investigated. The repellency of individual species was determined using a Y-tube olfactometer. Our results showed that volatiles of five plant species were highly effective in repelling ACP with repellency as much as 76%. Among these, the tree species, Camptotheca acuminate, and the two shrubs, Lantana camara and Mimosa bimucronata, could potentially be planted as a landscape barrier. The two herbs, Capsicum annuum and Gynura bicolor, could potentially be used as interrow plantings in orchards. This is the first time that the repellency of fresh tissues from a diverse range of plant species to ACP has been determined. Although further field evaluation of various interplanting regimes and landscape barriers are needed to assess their effectiveness, our results showed that these aromatic species, being highly repellent to ACT, offer great potential as more cost-effective and environmentally sustainable alternatives to the current methods of managing HLB.

Interspecific hybrid frequencies can vary considerably across contact zones of a single pair of progenitor species. The reasons for this are not well understood, but could help explain processes such as species diversification or the range expansion of invasive hybrids. The widespread cattails Typha latifolia and T. angustifolia seldom hybridize in some parts of their range, but in other areas produce the dominant hybrid T. × glauca. We used a combination of field and greenhouse experiments to investigate why T. × glauca has invaded wetlands in the Laurentian Great Lakes region of southern Ontario, Canada, but is much less common in the coastal wetlands of Nova Scotia in eastern Canada. One potentially important environmental difference between these two regions is salinity. We therefore tested three hypotheses: 1) T. latifolia and T. angustifolia in Nova Scotia are genetically incompatible; 2) the germination or growth of T. × glauca is reduced by salinity; and 3) T. latifolia, a main competitor of T. × glauca, is locally adapted to saline conditions in Nova Scotia. Our experiments showed that Nova Scotia T. latifolia and T. angustifolia are genetically compatible, and that saline conditions do not impede growth of hybrid plants. However, we also found that under conditions of high salinity, germination rates of hybrid seeds were substantially lower than those of Nova Scotia T. latifolia. In addition, germination rates of Nova Scotia T. latifolia were higher than those of Ontario T. latifolia, suggesting local adaptation to salinity in coastal wetlands. This study adds to the growing body of literature which identifies the important roles that local habitat and adaptation can play in the distributions and characteristics of hybrid zones.

The interannual variation (IAV) of net ecosystem carbon production (NEP) plays an important role in understanding the mechanisms of the carbon cycle in the agriculture ecosystem. NEP is usually partitioned into the diffecence between gross ecosystem productivity (GEP) and ecosystem respiration (RE), or the integration of the carbon uptake or release peak and the corresponding duration. In this study, the climatic and biotic controls of the IAV of NEP, which were expressed as annual values and anomalies, were investigated based on an eddy covariance dataset of rain-fed spring maize during 2005–2018 in the northeast of China. The annual NEP was 270±115 g C m−2yr −1. Annual values and anomalies of NEP were positively correlated with that of precipitation (PPT), GEP and daily maximum NEP (NEPmax). 78.9% of annual anomalies of NEP were explained by the interaction of climate, soil and plant variables, and the atmospheric water vapor deficit (VPD) played a dominated role. Annual anomalies of NEP were dominantly and positively controlled by the soil water content (SWC) through GEP and the soil temperature (Ts) through RE. In comparison, annual anomalies of NEP were dominantly and negatively controlled by summer VPD through the NEPmax, positively adjusted by spring precipitation and the effective accumulative temperature through the beginning date (BDOY) of the affecting carbon uptake period (CUP), and by autumn precipitation and leaf area index through the end date (EDOY) of the affecting CUP. Residues restrained the carbon release at the beginning of the year, and accelerated the carbon release at the end of the year. Our results hightlight that NEP might be more sensitive to the change of water condition (such as PPT, SWC and VPD) induced by the climate changes.

Earthworms are a major component of soil fauna communities with positive effects on soil chemical, biological and physical processes. A study was carried out at Chinhoyi University of Technology experimental farm, Zimbabwe, to investigate the medium-term effects of cultural practices on earthworm communities in a maize-based cropping system. Data were collected in the 2018/2019 cropping season from a six-year old experiment with tillage system (conventional, rip line seeding and basin planting), fertiliser application rate (zero, low: 35.2 kg ha−1 N + 12.2 kg ha−1 P2O5 + 6.6 kg ha−1K2O, medium: 41.5 kg ha−1 N + 14 kg ha−1 P2O5 + 7 kg ha−1 K2O, and high: 83 kg ha−1 N + 28 kg ha−1 P2O5: 14 kg ha−1 K2O.) and weeding intensity (twice, four times and clean weeding) as the main, sub- and sub-subplots, respectively. Lumbricus (34.4%) and Diplocardia (38.3%) were the dominant genera while endogeic earthworms (48.4%) dominated the community structure among other earthworm functional groups. Lumbricus abundance, total earthworm abundance, genus richness and Shannon diversity index were higher in clean weeded plots under the basin planting system relative to other treatments. Inorganic fertiliser application in the conventional tillage (CT) system reduced Eisenia abundance and genus richness. There was a positive correlation between total earthworm abundance (r = 0.34, P < 0.001) and negative correlation of Diplocardia abundance (r = -21, P < 0.05) with maize grain yield. These results suggest that in minimum tillage systems clean weeding has positive effects on earthworms while in CT, application of high doses of inorganic fertiliser is detrimental to earthworm communities.

The theory of ecological divergence provides a useful framework to understand the adaptation of many species to anthropogenic (‘domestic’) habitats. The mosquito Aedes aegypti, a global vector of several arboviral diseases, presents an excellent study system. Ae. aegypti originated in African forests, but the populations that invaded other continents have specialized in domestic habitats. In its African native range, the species can be found in both forest and domestic habitats like villages. A crucial behavioral change between mosquitoes living in different habitats is their oviposition choices. Forest Ae. aegypti lay eggs in natural water containers like tree holes, while their domestic counterparts heavily rely on artificial containers such as plastic buckets. These habitat-specific containers likely have different environmental conditions, which could drive the incipient divergent evolution of oviposition in African Ae. aegypti. To examine this hypothesis, we conducted field research in two African locations, La Lopé, Gabon and Rabai, Kenya, where Ae. aegypti live in both forests and nearby villages. We first characterized a series of environmental conditions of natural oviposition sites, including physical characteristics, microbial density, bacterial composition, and volatile profiles. Our data showed that in both locations, environmental conditions of oviposition sites did differ between habitats. To examine potential behavioral divergence, we then conducted field and laboratory oviposition choice experiments to compare the oviposition preference of forest and village mosquitoes. The field experiment suggested that forest mosquitoes readily accepted artificial containers. In laboratory oviposition assays, forest and village mosquito colonies did not show a differential preference towards several conditions that featured forest versus village oviposition sites. Collectively, there is little evidence from our study that environmental differences lead to strong and easily measurable divergence in oviposition behavior between Ae. aegypti that occupy nearby forest and domestic habitats within Africa, despite clear divergence between African and non-African Ae. aegypti.

Aims The impact of nutrient increase on nutrient resorption from senescent leaves is an important topic, which is not completely understood. Mangrove species are characterized by nutrient conservation mechanisms as a consequence of adaptation to nutrient-poor environments. The understanding of the response of the traits related to nutrient conservation strategies to nutrient availability is limited. This study aims to address whether nutrient resorption of mangrove species is responsive to long-term nutrient enrichment. Methods A field-based study was carried out in a Kandelia obovata dominated mangrove stand where a nutrient gradient was generated by the long-term discharge of aquaculture wastewater. Seasonal variations of nutrient resorption and nutrient availability were assessed. Important findings The data from summer and winter showed the same results: 1) resorption proficiency or the nutrient concentrations (N and P) in senescent leaves did not varied with nutrient increases except the plot that the N availability was extremely high; 2) the resorption efficiency of both N and P was positively correlated with nutrient availability, and N resorption efficiency was also positively correlated to leaf N: P ratio; 3) N resorption was complete while the resorption of P was incomplete. These results indicate that resorption proficiency of K. obovata is less sensitive than resorption efficiency to nutrient availability, and the positive response of N resorption efficiency is related to the imbalance of nutrient availability, while the positive response of P resorption efficiency is unrelated to plant nutrient status. We suggest that caution should be taken in using resorption efficiency of mangrove species to predict plant nutrient status.