Plant Coexistence Research Articles

Effect of microplastics on the allelopathic effects of native and invasive plants on co-occurring invaders.

Microplastic pollution has emerged as a significant global change factor, with the potential to alter the biological, physicochemical properties of soil and to subsequently affect plant growth. Despite growing recognition of the impacts of microplastic pollution, the mechanisms by which microplastics modify plant leaf chemistry and influence allelopathic interactions among co-existing plant species remain unclear. We used the native perennial forb Achyranthes bidentata and the invasive annual forb Amaranthus spinosus as focal species. We grew the two species with and without competition with each other. This setup was further combined with a treatment involving the addition of polyethylene (PE). We then testd the effects of aqueous extract on seed germination and seedling growth for five invasive and five native species. Subsequently, metabolomic analysis was conducted on the aqueous extracts, in which significant allelopathic effects were observed on test species. The presence of PE microplastics enhanced the biomass of both Achyranthes and Amaranthus under competitive and non-competitive growth conditions. Furthermore, PE microplastics were found to induce a negative allelopathic effect for the native plant Achyranthes on co-occurring plants, which appeared to be mediated through changes in leaf chemistry. Bisdemethoxycurcumin, ethylparaben, salicin 6'-sulfate and 5-hydroxy-3',4',7-trimethoxyflavone glucoside were proven important compounds for allelopathic enhancement. Overall, these results suggest that microplastic pollution has the capability to influence the co-existence of invasive and native plants by altering their allelopathic potential. This insight into the interactions between microplastics and plant allelopathy provides a novel perspective on how microplastic pollution could modify plant species interactions and ecosystem dynamics. Future studies could aim to answer how microplastics might affect plant root exudates and whether this process would mediate biological invasion.

Soil mycobiome dissimilarity, independent of fungal guild, is associated with increased probability of plant coexistence

Abstract Major theories regarding microbe‐mediated plant community dynamics assume that plant species cultivate distinct microbial communities. However, few studies empirically assess the role of species‐associated microbial community dissimilarity in plant competitive dynamics. In this study, we paired a competition experiment between eight annual forbs with characterisation of species‐associated fungal communities to assess whether mycobiome dissimilarity is associated with pairwise competitive dynamics. Using a quantitative approach informed by modern coexistence theory, we found that fungal dissimilarity was correlated with both increased stabilising niche differences and fitness inequalities. Additionally, we found that the probability of coexistence increased with mycobiome dissimilarity. When subsetting the community into different fungal functional groups (pathotrophs, saprotrophs, symbiotrophs), overall relationships between dissimilarity and competitive dynamics were independent of these functional groups. Synthesis. These results suggest that fungal community divergence may play an important role in mediating plant competitive dynamics. Although fungal community dissimilarity is associated with both niche and fitness differences, complex biotic and/or abiotic interactions below‐ground may result in an observed correlation between fungal community dissimilarity and plant coexistence. Ultimately, this study suggests a novel approach to better understanding how microbiome dissimilarity may impact host community dynamics.

Root traits and soil legacies drive species competition outcomes

Abstract Plant competition can be affected by plant functional traits but also by differences in fitness mediated by soil microbes. Climatic conditions such as drought further influence plant competition. Yet little is known about how soil microbes and drought interact with plant species that have distinct root traits and how this influences plant competition outcomes. We grew three plant species that co‐occur in temperate grasslands in China (Stipa krylovii, Artemisia frigida, Agropyron cristatum) in monocultures and mixtures and subjected the plant combinations to five soil inocula (root‐associated soil of S. krylovii, A. frigida, A. cristatum, an equal mixture of the three root zone soils and sterilized soil) as well as to a drought treatment. The relative change in plant biomass was used to determine plant competition outcomes. The three species exhibited clear differences in competitive abilities with A. cristatum > S. krylovii > A. frigida, and soil inocula or the drought treatment did not change the order. The relative yield (RY) of plants was affected by soil inocula, drought and plant arrangement. The strongest competitor, A. cristatum, with high total root length, root surface area and root volume experienced more negative biotic feedback, and drought enhanced the magnitude of these negative effects. On the contrary, the most inferior competitor, A. frigida, with high specific root length tended to have neutral or positive biotic feedback, and drought had no effect. Furthermore, the RY and fitness difference (reflected as the competitive ability in the mixture) of the three species were differentially influenced by root traits and plant–soil feedback. RY of A. cristatum could be predicted by the feedback effect in the mixture, and the fitness difference was mainly related to root traits. Both RY and fitness differences of A. frigida (the weakest competitor) could be predicted by root trait differences and feedback effects. Differences in root traits were the best predictors of the intermediate competitor S. krylovii. Our study shows that competition outcomes of co‐existing species depend on root traits and species‐specific PSF effects in mixture. Future work should examine the mechanisms that explain how plant competition and soil microbial heterogeneity act in conjunction with climate change in influencing plant coexistence. Read the free Plain Language Summary for this article on the Journal blog.

Mechanisms of coexistence: Exploring species sorting and character displacement in woody plants to alleviate belowground competition.

Rarely do we observe competitive exclusion within plant communities, even though plants compete for a limited pool of resources. Thus, our understanding of the mechanisms sustaining plant biodiversity might be limited. In this study, we explore two common ecological strategies, species sorting and character displacement, that promote coexistence by reducing competition. We assess the degree to which woody plants may implement these two strategies to lower belowground competition for nutrients which occurs via nutritional (mostly mycorrhizal) mutualisms. First, we compile data on plant traits and the mycorrhizal association state of woody angiosperms using a global inventory of indigenous flora. Our analysis reveals that species in locations with high mycorrhizal diversity exhibit distinct mean values in leaf area and wood density based on their mycorrhizal type, indicating species sorting. Second, we reanalyse a large dataset on leaf area to demonstrate that in areas with high mycorrhizal diversity, trees maintain divergent leaf area values, showcasing character displacement. Character displacement among plants is considered rare, making our observation significant. In summary, our study uncovers a rare occurrence of character displacement and identifies a common mechanism employed by plants to alleviate competition, shedding light on the complexities of plant coexistence in diverse ecosystems.

Time-dependent interaction modification generated from plant-soil feedback.

Pairwise interactions between species can be modified by other community members, leading to emergent dynamics contingent on community composition. Despite the prevalence of such higher-order interactions, little is known about how they are linked to the timing and order of species' arrival. We generate population dynamics from a mechanistic plant-soil feedback model, then apply a general theoretical framework to show that the modification of a pairwise interaction by a third plant depends on its germination phenology. These time-dependent interaction modifications emerge from concurrent changes in plant and microbe populations and are strengthened by higher overlap between plants' associated microbiomes. The interaction between this overlap and the specificity of microbiomes further determines plant coexistence. Our framework is widely applicable to mechanisms in other systems from which similar time-dependent interaction modifications can emerge, highlighting the need to integrate temporal shifts of species interactions to predict the emergent dynamics of natural communities.

Impacts of Soil Properties on Species Diversity and Structure in Alternanthera philoxeroides-Invaded and Native Plant Communities.

Soil properties can affect plant population dynamics and the coexistence of native and invasive plants, thus potentially affecting community structure and invasion trends. However, the different impacts of soil physicochemical properties on species diversity and structure in native and invaded plant communities remain unclear. In this study, we established a total of 30 Alternanthera philoxeroides-invaded plots and 30 control plots in an area at the geographical boundary between North and South China. We compared the differences in species composition between the invaded and native plant communities, and we then used the methods of regression analysis, redundancy analysis (RDA), and canonical correspondence analysis (CCA) to examine the impacts of soil physicochemical properties on four α-diversity indices and the species distribution of these two types of communities. We found that A. philoxeroides invasion increased the difference between the importance values of dominant plant species, and the invasion coverage had a negative relationship with the soil-available potassium (R2 = 0.135; p = 0.046) and Patrick richness index (R2 = 0.322; p < 0.001). In the native communities, the species diversity was determined with soil chemical properties, the Patrick richness index, the Simpson dominance index, and the Shannon-Wiener diversity index, which all decreased with the increase in soil pH value, available potassium, organic matter, and ammonium nitrogen. However, in the invaded communities, the species diversity was determined by soil physical properties; the Pielou evenness index increased with increasing non-capillary porosity but decreased with increasing capillary porosity. The determinants of species distribution in the native communities were soil porosity and nitrate nitrogen, while the determinants in the invaded communities were soil bulk density and available potassium. In addition, compared with the native communities, the clustering degree of species distribution in the invaded communities intensified. Our study indicates that species diversity and distribution have significant heterogeneous responses to soil physicochemical properties between A. philoxeroides-invaded and native plant communities. Thus, we need to intensify the monitoring of soil properties in invaded habitats and conduct biotic replacement strategies based on the heterogeneous responses of native and invaded communities to effectively prevent the biotic homogenization that is caused by plant invasions under environmental changes.

Quantifying soil microbial effects on plant species coexistence: A conceptual synthesis.

Soil microorganisms play a critical role in shaping the biodiversity dynamics of plant communities. These microbial effects can arise through direct mediation of plant fitness by pathogens and mutualists, and over the past two decades, numerous studies have shined a spotlight on the role of dynamic feedbacks between plants and soil microorganisms as key determinants of plant species coexistence. Such feedbacks occur when plants modify the composition of the soil community, which in turn affects plant performance. Stimulated by a theoretical model developed in the 1990s, a bulk of the empirical evidence for microbial controls over plant coexistence comes from experiments that quantify plant growth in soil communities that were previously conditioned by conspecific or heterospecific plants. These studies have revealed that soil microbes can generate strong negative to positive frequency-dependent dynamics among plants. Even as soil microbes have become recognized as a key player in determining plant coexistence outcomes, the past few years have seen a renewed interest in expanding the conceptual foundations of this field. New results include re-interpretations of key metrics from classic two-species models, extensions of plant-soil feedback theory to multispecies communities, and frameworks to integrate plant-soil feedbacks with processes like intra- and interspecific competition. Here, I review the implications of theoretical developments for interpreting existing empirical results and highlight proposed analyses and designs for future experiments that can enable a more complete understanding of microbial regulation of plant community dynamics.

Seed germination and seedling growth response of Leymus chinensis to the allelopathic influence of grassland plants.

Allelopathy has a profound impact on the germination and growth of plants, influencing the establishment of plant populations and shaping community ecological patterns. However, the allelopathic potential of many grassland species remains poorly understood. In this study, we prepared aqueous extracts from 17 herbaceous plants to investigate their allelopathic effects on the seed germination and seedling growth of Leymus chinensis, a dominant grassland species. Our results revealed that the response of L. chinensis to allelopathic compounds was dependent on the specific plant species, extract concentration, and target plant organ. Notably, Fabaceae plants exhibited a stronger allelopathic potential than Poaceae, Asteraceae, and other plant families. Moreover, we observed that root growth of L. chinensis was more sensitive to allelopathy than shoot growth, and seed germination was more affected than seedling growth. Generally, the germination of L. chinensis was strongly inhibited as the donor plant extract concentration increased. The leachate of Fabaceae plants inhibited the seedling growth of L. chinensis at concentrations ranging from 0.025 to 0.1 g mL-1. On the other hand, the leachate from other families' plants exhibited either inhibitory or hormetic effects on the early growth of L. chinensis, promoting growth at 0.025 g mL-1 and hindering it at concentrations between 0.05 and 0.1 g mL-1. These findings highlight the significant allelopathic potential of grassland plants, which plays a critical role in establishing plant populations and associated ecological processes. In addition, they shed light on the coexistence of other plants with dominant plants in the community.

Chemically Mediated Plant-Plant Interactions: Allelopathy and Allelobiosis.

Plant-plant interactions are a central driver for plant coexistence and community assembly. Chemically mediated plant-plant interactions are represented by allelopathy and allelobiosis. Both allelopathy and allelobiosis are achieved through specialized metabolites (allelochemicals or signaling chemicals) produced and released from neighboring plants. Allelopathy exerts mostly negative effects on the establishment and growth of neighboring plants by allelochemicals, while allelobiosis provides plant neighbor detection and identity recognition mediated by signaling chemicals. Therefore, plants can chemically affect the performance of neighboring plants through the allelopathy and allelobiosis that frequently occur in plant-plant intra-specific and inter-specific interactions. Allelopathy and allelobiosis are two probably inseparable processes that occur together in plant-plant chemical interactions. Here, we comprehensively review allelopathy and allelobiosis in plant-plant interactions, including allelopathy and allelochemicals and their application for sustainable agriculture and forestry, allelobiosis and plant identity recognition, chemically mediated root-soil interactions and plant-soil feedback, and biosynthesis and the molecular mechanisms of allelochemicals and signaling chemicals. Altogether, these efforts provide the recent advancements in the wide field of allelopathy and allelobiosis, and new insights into the chemically mediated plant-plant interactions.

Facilitation against herbivory more important than resource‐based niche differences for plant coexistence in a field experiment

Abstract Theory suggests that eutrophication impacts plant community biodiversity by constraining niche differences and increasing competitive inequalities among species, leading to the exclusion of weaker competitors. However, explicit tests of nutrient effects on the strength and direction of inter‐ and intraspecific plant–plant interactions that dictate coexistence are lacking, especially in complex field settings where multiple processes can simultaneously affect plant growth and reproduction. We conducted a field experiment in southeastern Vancouver Island, Canada, using four annual grassland plant species to test how species interactions responded to eutrophication and the covariation of herbivore pressure and neighbour species light‐ and moisture‐use. We found that focal species reproduction was limited by nutrient availability and herbivory, such that the nature of species interactions was context‐dependent. Competitive interactions failed to predict species persistence under these conditions. Instead, facilitation was critical—phytometers grown without neighbours consistently failed to produce seed under herbivore pressure meaning that fecundity significantly increased with neighbour density. Synthesis. Our work demonstrates the importance of species interactions in plant community responses to eutrophication but emphasizes that ‘indirect’ drivers of plant performance may influence or overwhelm nutrient effects on plant–plant competition. The widespread occurrence of mortality overcome primarily by facilitation highlights the importance of positive density dependence. Overall, our results suggest that knowledge of resource niche overlap may be insufficient to explain plant community responses to eutrophication. This highlights the necessity of considering the broader environmental context when leveraging ecological theory to understand global change effects in empirical settings.

Design and performance analysis of thermal assisted reverse osmosis (RO)

Abstract Today, the world is facing difficult challenges related to water scarcity and freshwater resources. Water desalination has become necessary to meet this great demand. The reverse osmosis desalination system is considered the dominant type of desalination, although the high amount of energy consumed is considered the main barrier to expanding seawater reverse osmosis (SWRO). The need for producing an environmentally friendly energy source is also one of the most important challenges in preserving the environment and reducing global warming. The coexistence of power plants that release waste heat energy through the condenser and reverse osmosis plant represents an opportunity for a synergy system. Therefore, research has shown that the low/ultralow grade heat from natural sources or industrial processes can assist the process of desalination. This paper reviews available process configurations, system design, and operating parameters, and discusses the performance of the RO process at high temperatures.

Correlations of the root–shoot ratio with soil water content in the patchy alpine grassland of the north‐eastern Qinghai–Tibetan Plateau using electrical resistivity tomography

AbstractThe root–shoot biomass ratio (R:S) changing the soil water redistribution is not well understood due to a lack of nondestructive technology to characterize the coexistence of plants and soil. This study aims to assess the correlations of the R:S ratios of Achnatherum splendens with soil water content by electrical resistivity tomography (ERT) on the north‐western Qinghai–Tibet Plateau (QTP). During the growing season, an experimental plot including bare patches (BK) and low‐ (LD) and high‐density (HD) A. splendens subplots was designed to quantify soil volumetric water content under different soil depths and antecedent total precipitation conditions for 7 days (AP7). The results showed that the R:S ratio was positive with soil water content in the surface soil layer of 0–10 cm. The synergistic effect of the R:S ratio on soil water in the surface soil layer promoted an increase in surface soil water. However, the nonsynergistic effect in the middle soil layer weakened the soil water increasing, and the effect of the R:S ratio on soil water in the deep soil layer of 40–80 cm was not obvious. In HD, soil water increased between 0.08% and 0.95% and was highest under AP7 &gt; 20 mm conditions. In LD, soil water increased in the surface and deep soil layers but decreased in the middle soil layer, especially under AP7 = 10–20 mm conditions (−1.23%). These findings provide valuable insights that patchy alpine grass survival strategy under future climate change on the QTP, and the results are beneficial to the development of soil–plant–atmosphere continuum models.

The effect of moisture on nitrogen acquisition strategies of ephemeral desert plants in north-western China are regulated by temperature

AimsSymbiotic plants achieve partitioning of shared resources by chemical nutrient niche separation to escape competition. Understanding whether the nitrogen(N) nutrient acquisition strategies of ephemeral plants are influenced by temperature and moisture can facilitate the elucidation of plant coexistence strategies in desert ecosystems under environmental change. This study aimed to see whether changes in temperature and moisture affected the preferential uptake of different N chemotypes by ephemerals. MethodsIn this study, four dominant ephemerals in the Gurbantunggut Desert, Eremopyrum orientale, Erodium oxyrhinchum, Centaurea pulchella, and Lappula patula, were selected for controlled experiments in indoor pots. We conducted a short-term 15N follow-up experiment on potted treatments by setting two temperature gradients (low temperature(T1): 15 °C during the day and 5 °C at night; high temperature(T2): 25 °C during the day and 15 °C at night) and three moisture gradients (drought treatment(W1): soil moisture content of 2%; normal moisture treatment(W2): soil moisture content of 8%; wet treatment(W3): soil moisture content of 14%). Results Four ephemerals preferentially absorbed 15N-NH4 at low temperature treatment (T1), with a contribution ranging from 17.33% to 55.11%. The greatest uptake rate of 15N-NH4 was at the low temperature-normal moisture treatment (T1W2), and the fastest N uptake rate among the four plants could reach 13.84 μg·h–1, while at the high temperature-drought treatment (T2W1), the uptake was the smallest. However, plants showed the greatest preference for 15N-NO3 uptake at the high temperature treatment, with contributions ranging from 16.09% to 54.06%. The uptake rate of 15N-NO3 was greatest at the high temperature-wet treatment (T2W3), where the fastest N uptake rate among the four plants could reach 12.48 μg·h–1, and the smallest rate of 15N-NO3 at the low temperature-drought treatment (T1W1). The four ephemerals could also absorb organic N, 15N-Glycine, especially at the low temperatures. ConclusionsThe results showed that the four plants exhibited “Plasticity” in the uptake of the three N forms under different hydrothermal conditions. The effect of temperature and moisture interaction is more reflective of the N acquisition pattern of ephemeral plants in the desert. In low temperature environments, the uptake preference of ephemerals for N forms was mainly regulated by water, while in high temperature environments, the uptake of N forms by ephemerals was mainly regulated by temperature.

Pollinator-mediated plant coexistence requires high levels of pollinator specialization.

In pollen-limited plant communities, the foraging behavior of pollinators might mediate coexistence and competitive exclusion of plant species by determining which plants receive conspecific pollen. A key question is whether realistic pollinator foraging behavior promotes coexistence or exclusion of plant species. We use a simulation model to understand how pollinator foraging behavior impacts the coexistence dynamics of pollen-limited plants. To determine whether pollinators are likely to provide a biologically important coexistence mechanism, we compare our results to bee foraging data from the literature and from a novel experimental analysis. Model results indicate that strong specialization at the level of individual foraging paths is required to promote coexistence. However, few empirical studies have robustly quantified within-bout specialization. Species-level data suggest that foraging behavior is sufficient to permit pollinator-mediated coexistence in species-poor plant communities and possibly in diverse communities where congeneric plants co-occur. Our experiments using bumblebees show that individual-level specialization does exist, but not at levels sufficient to substantially impact coexistence dynamics. The literature on specialization within natural foraging paths suffers from key limitations, but overall suggests that pollinator-mediated coexistence should be rare in diverse plant communities.

Interplant carbon and nitrogen transfers mediated by common arbuscular mycorrhizal networks: beneficial pathways for system functionality.

Arbuscular mycorrhizal fungi (AMF) are ubiquitous in soil and form nutritional symbioses with ~80% of vascular plant species, which significantly impact global carbon (C) and nitrogen (N) biogeochemical cycles. Roots of plant individuals are interconnected by AMF hyphae to form common AM networks (CAMNs), which provide pathways for the transfer of C and N from one plant to another, promoting plant coexistence and biodiversity. Despite that stable isotope methodologies (13C, 14C and 15N tracer techniques) have demonstrated CAMNs are an important pathway for the translocation of both C and N, the functioning of CAMNs in ecosystem C and N dynamics remains equivocal. This review systematically synthesizes both laboratory and field evidence in interplant C and N transfer through CAMNs generated through stable isotope methodologies and highlights perspectives on the system functionality of CAMNs with implications for plant coexistence, species diversity and community stability. One-way transfers from donor to recipient plants of 0.02-41% C and 0.04-80% N of recipient C and N have been observed, with the reverse fluxes generally less than 15% of donor C and N. Interplant C and N transfers have practical implications for plant performance, coexistence and biodiversity in both resource-limited and resource-unlimited habitats. Resource competition among coexisting individuals of the same or different species is undoubtedly modified by such C and N transfers. Studying interplant variability in these transfers with 13C and 15N tracer application and natural abundance measurements could address the eco physiological significance of such CAMNs in sustainable agricultural and natural ecosystems.

Data from: Drought alters soil microbiome-mediated plant coexistence

Data from: Drought alters soil microbiome-mediated plant coexistence

Determination of Paleoenvironmental Changes by Using δ13C, 14C Dating and Rb/Sr Ratio in Critical Karst Area of Yunnan-Guizhou Plateau, Southwestern China

Paleosols preserve archives of vegetation history, environmental changes, and sedimentary systems. The changes in vegetation history and environmental conditions in karst areas of the Yunnan–Guizhou plateau of southwestern China since the late Pleistocene were analyzed using δ13C, 14C and the Rb/Sr ratio. Our δ13C results reveal the coexistence of C3 and C4 plants (−10.91 to −30.45‰) in soil organic matter, something that is consistent with the present field vegetation assessment. The large vertical difference in the δ13C value (&gt;4‰) is related to the cultivation of agricultural crops and to changes in environmental conditions. Furthermore, the variation in δ13C values was influenced by the summer monsoon climate of the Indian Ocean and east Asia. We found that total organic carbon (TOC) concentration decreased exponentially with soil depth, indicating high carbon loss. In addition, 14C apparent age of the soil profiles ranged from modern times to 20,605 (±63) years before the present (yrs. BP) and is positively correlated with soil depth. The combined results indicate that, since the late Pleistocene era, environmental conditions in the study area have changed intermittently on a scale of millennia from hot-humid to cold-dry conditions. We speculate that there may have been extreme climate events in the study area 14,750 years BP, which are marked by a drastic change in δ13C and in the Rb/Sr ratio.

Patterns of frequency and density dependence are highly variable in diverse annual flowering plant communities.

Applications of ecological theory to natural communities often assume that competitive, negative density-dependent processes are the only type of interaction important for diversity maintenance. Recent advances suggest that positive interactions within trophic levels (e.g. plant-plant) may also affect plant coexistence. Though positive plant-plant interactions theoretically might result in positive or nonmonotonic frequency or density dependence (FD/DD), less is known about how commonly these patterns occur, or which ecological processes might result in such patterns in natural plant communities. In this study we test for signals of variable frequency and density dependence in annual flowering plant communities in Western Australia, and search for evidence that interactions among plants during flowering might induce positive or nonmonotonic FD/DD in flowering plants. Using four common annual wildflower species, we ask if plant fecundity exhibits positive or nonmonotonic FD/DD, and if pollinator-mediated plant-plant interactions during flowering change patterns of FD/DD relative to pollinator-independent plant interactions. Three species exhibited nonmonotonic (hump-shaped) density dependence, and only one species experienced strictly negative density dependence. Each species exhibited a different pattern of frequency dependence (positive, negative, weakly nonmonotonic, and no detectable frequency dependence). Pollinator-mediated plant-plant interactions during flowering induced both nonmonotonic density dependence and negative frequency dependence in one species. Importantly, the extent of variation in FD/DD observed in our study brings into question the dominance of negative density and frequency dependence in theory, suggesting instead that demographic responses of plants to their communities fall along a continuum of possible density- and frequency-dependent patterns.

Pollinator sex matters in competition and coexistence of co-flowering plants

Male and female pollinators often exhibit sex-specific preferences for visiting different flowers. Recent studies have shown that these preferences play an important role in shaping the network structure of pollination mutualism, but little is known about how they can mediate plant-plant interactions and coexistence of competing plants. The ecological consequences of sex-specific pollination can be complex. Suppose that a plant is favoured by female pollinators. They produce male pollinators, who may prefer visiting other competing plants and intensify the negative effects of inter-plant competition. Here, we analysed a simple two plant-one pollinator model with the sex structure of the pollinator. We observed that (i) sex-specific pollination can have complex consequences for inter-plant competition and coexistence (e.g. the occurrence of non-trivial alternative stable states in which one plant excludes or coexists with the other depending on the initial conditions), (ii) male and female pollinators have distinct ecological consequences because female pollinators have a demographic impact owing to reproduction, and (iii) plants are likely to coexist when male and female pollinators prefer different plants. These results suggest that sex-specific pollination is crucial for competition and coexistence of co-flowering plants. Future, pollination research should more explicitly consider the sex-specific behaviour of pollinating animals.

Characterization of Invasiveness, Thermotolerance and Light Requirement of Nine Invasive Species in China

Understanding responsible functional traits for promoting plant invasiveness could be important to aid in the development of adequate management strategies for invasive species. Seed traits play an important role in the plant life cycle by affecting dispersal ability, formation of the soil seed bank, type and level of dormancy, germination, survival and/or competitive ability. We assessed seed traits and germination strategies of nine invasive species under five temperature regimes and light/dark treatments. Our results showed a considerable level of interspecific variation in germination percentage among the tested species. Both cooler (5/10 °C) and warmer (35/40 °C) temperatures tended to inhibit germination. All study species were considered small-seeded, and seed size did not affect germination in the light. Yet, a slightly negative correlation was found between germination in the dark and seed dimensions. We classified the species into three categories according to their germination strategies: (i) risk-avoiders, mostly displaying dormant seeds with low G%; (ii) risk-takers, reaching a high G% in a broad range of temperatures; (iii) intermediate species, showing moderate G% values, which could be enhanced in specific temperature regimes. Variability in germination requirements could be important to explain species coexistence and invasion ability of plants to colonize different ecosystems.