Plant Population Dynamics Research Articles

Phenological development of barnyard grass plants originating from different geographical locations

AbstractBarnyard grass [Echinochloa crus‐galli (L.) Beauv] is a competitive C4 weed species that is widely distributed throughout the world. Although it originated in warm climatic conditions, currently, it is found in Europe as far north as Norway. This study aimed to compare the phenological development of plants from different climatic conditions in varying environmental conditions. To represent the contrasting climatic conditions within Europe, seeds were collected in Norway and Italy, and distributed to the study participants, to be sown at 10 different sites as two common populations. In addition to that, seeds of two to three local populations were collected near each of the sites. The development of the plants was monitored in a pot experiment set up under field conditions. The time to reach heading in the first year of the experiment was 77.6% faster (ranging from 45.9 to 98.3% on average) in the Norwegian than in the Italian population. However, in the leaf development stage, the difference between the common populations was smaller by, 23.5% on average (0–46.7%) and was mostly not significant. Our results indicate that different E. crus‐galli ecotypes, characterized by differences in their phenological development, evolved within the distribution area of this species in Europe. However, the early development of the plants progressed with negligible differences between populations. The findings reported here can be used to adapt existing models from one region to regions with different climatic conditions for use in decision support systems and for research into plant population dynamics.

Changes in climate, grazing pressure and nutrient inputs affect the structural integrity and functioning of Andean shrublands

ABSTRACT Background Changes in climate and the intensity of agriculture expansion can alter plant population dynamics and community composition and structure of dry shrublands. Aims We tested how temperature and moisture along an elevation gradient, grazing, and nutrient addition in soil affected demographic attributes of Croton shrubs and the composition and structure of plant species in an inter-Andean dry shrubland. Methods At three elevations, we installed grazing and exclusion plots, combined with four nutrient treatments: control, and addition of nitrogen (N), phosphorous (P) alone and in combination. We measured recruitment and survival of Croton seedlings, as well as survival, growth, fruiting of adult Croton and the composition and structure of neighbouring plants. Results Grazing exclusion improved adult survival of Croton at all three elevations. Grazing exclusion and addition of N and P increased adult growth of Croton at low and medium elevations. Croton seedling recruitment and survival decreased with distance to adult plants. The cover of Croton had a positive relationship with plant abundance and diversity. Conclusions Temperature, moisture, grazing and nutrient addition can alter the demography and cover of Croton, as well as the composition and structure of its neighbouring plants threatening the functioning of the inter-Andean dry shrubland.

Introduction: Will They Survive, Or Not?

IntroductionWill They Survive, Or Not? Jordan Sheridan (bio) and Nandini Thiyagarajan (bio) This collection of articles grew from a conference held in Hamilton, Ontario in 2017 titled "Resilience in a Multispecies World." Our multidisciplinary conference brought together artists, poets, activists, community members, and scholars from various stages in their careers to think critically about resilience in relation to nonhuman animals. We engaged many different platforms, from traditional panel discussions and keynote speakers to an art exhibit, quick panels based on keywords, hikes, and bird watching trips. We marveled at the resilience of "pests," such as cockroaches and bed bugs, and dived into the collective sadness of extinction and the limited resilience of animals we love. We thought carefully about the animals who live close to us and queried our responsibilities to them. What emerged from this conference was a clear sense that thinking about animals and resilience together—not only in relation to conservation—was urgent, necessary, and a much larger conversation than we could have in three days. The articles collected in this cluster cover a lot of ground but they are just the tip of the iceberg. The concept of resilience is central to how ecologists analyze and manage the population dynamics of plants and animals within an ecosystem. In 1973, forest ecologist C. S. Holling introduced the concept of resilience to describe the ability of an ecological system to withstand, absorb, or fortify against disturbances in a way that still maintains its basic structures.1 Since the early 1980s, ecologists have developed a significant body of theoretical and mathematical models for measuring, understanding, and predicting resilience on the level of populations and ecosystems.2 In recent years the concept has crept into a wide array of social and political fields such as international finance and [End Page 62] economics, corporate risk analysis, urban planning and development, public health, and psychology. Susie O'Brien argues that "in the course of gaining scientific rigor, resilience has not lost its popular appeal as the anchoring idea of a powerful story in which moralism and hope combine to produce a successful outcome."3 What O'Brien calls "resilience stories" is a useful term here because it helps us conceptualize the cultural circulation of animal resilience. She argues that the primary normative neoliberal function of these stories "suggests that we thrive not in spite of upheaval but because of it."4 The concept of "resilience stories" allows us to think about resilience in relation to animals and to understand the politics circulating in such stories. The neoliberal function of resilience stories that urges us to thrive in the face of upheaval and hardship meets a limit when applied to animals. In the Anthropocene, wild animals face anthropogenic threats to their habitat and livelihood and many are not thriving. We understand animal resilience along three lines. First, animals who are not fit for this changing world become signals to indicate the need for human intervention, innovation, and technology. Second, domesticated animals, such as agricultural animals and animals used in scientific experiments, are genetically modified or "enhanced" to be more resilient to disruptions, which are normalized as natural parts of a changing world. Third, more synanthropic animals who demonstrate a confounding level of resilience are seen as pests, symbols, or emblems of the end of the world. Rarely do we focus on animals as individuals or communities with stories of loss, survival, and adaptation that are more complex than simply becoming emblems of the Anthropocene. By casting a light on animals and resilience, this cluster of articles aims to reframe and challenge how resilience is conceptualized. This special cluster of articles draws together diverse perspectives on the question of multispecies resilience and its critical theoretical possibilities. And yet in the overall picture presented here, as Susie O'Brien notes in the afterword, multispecies resilience "doesn't really get at what it wants to describe."5 In this introduction we take this to mean that while multispecies resilience is not fully realized, we can think about how it emerges in various examples as in-process, incomplete, and troubled potentialities. The essays gathered here take up issues that arise in environmental politics and bring them...

Prescribed burning has limited effects on the population dynamics of rare plants

AbstractRare species serve important ecosystem functions, including community resilience to global change. Yet rare species are disappearing globally because of anthropogenic activities such as fire suppression. Prescribed burning is a widespread management approach that can reduce invasive plant presence, recycle nutrients, and restore species diversity. However, the effects of prescribed burning on rare plants are not well understood. We analyzed the population dynamics of 67 rare, native plant species in response to prescribed burning using the Chicago botanic garden's Plants of Concern dataset. This dataset includes rare plant populations concentrated in the northeast part of Illinois, and a few populations in Indiana and Wisconsin, United States. We evaluated the effects of burning by comparing the percent change in population size in the short‐term (1–2 years) and long‐term (3–4 years) after prescribed burning, to the percent change in population size not following burns. In a global model with all species, we did not detect the effects of burning on percent change in population size. In species‐level analyses, we detected burn effects for most species for which we had the statistical power to detect possible burn responses, although the direction of their responses was mixed. Five species responded consistently between short‐ and long‐term datasets, and four species had mixed responses, with most responding positively over the short‐term and negatively over the long‐term. We complemented this analysis with a literature review of fire responses for available species. Our literature review revealed more responses to burning than what we found from our analyses; however, most of this evidence does not compare burned and unburned populations directly and should be treated cautiously. Through community science monitoring efforts, we were able to compile one of the largest studies of burn effects on rare plants to date, but continued monitoring is necessary to fully evaluate how prescribed burning impacts rare plant species.

Plant responses to soil biota depend on precipitation history, plant diversity, and productivity.

Soil biota are critical drivers of plant growth, population dynamics, and community structure and thus have wide-ranging effects on ecosystem function. Interactions between plants and soil biota are complex, however, and can depend on the diversity and productivity of the plant community and environmental conditions. Plant-soil biota interactions may be especially important during stressful periods, such as drought, when plants can gain great benefits from beneficial biota but may be susceptible to antagonists. How soil biota respond to drought is also important and can influence plant growth following drought and leave legacies that affect future plant responses to soil biota and further drought. To explore how drought legacies and plant community context influence plant growth responses to soil biota and further drought, we collected soils from 12 grasslands varying in plant diversity and productivity where precipitation was experimentally reduced. We used these soils as inoculum in a growth chamber experiment testing how precipitation history (ambient or reduced) and soil biota (live or sterile soil inoculum) mediate plant growth and drought responses within an experimental plant community. We also tested whether these responses differed with the diversity and productivity of the community where the soil was collected. Plant growth responses to soil biota were positive when inoculated with soils from less diverse and productive plant communities and became negative as the diversity and productivity of the conditioning community increased. At low diversity, however, positive soil biota effects on plant growth were eliminated if precipitation had been reduced in the field, suggesting that diversity loss may heighten climate change sensitivity. Differences among species within the experimental community in their responses to soil biota and drought suggest that species benefitting from less drought sensitive soil biota may be able to compensate for some of this loss of productivity. Regardless of the plant species and soil origin, further drought eliminated any effects of soil biota on plant growth. Consequently, soil biota may be unable to buffer the effects of drought on primary productivity or other ecosystem functions as extreme events increase in frequency.

¿Cómo afecta el ganado doméstico a la biomasa y la fecundidad de distintos tipos sucesionales de especies en el Monte Patagónico?

Plants respond to disturbances according to their physiological characteristics, their lifeform, and their ecological role or function within the community. We assessed the response, in terms of biomass and fitness, to a gradient of stocking density (measured as livestock units.year.ha-1) considering different successional types of species (early, intermediate and late species) from Patagonian Monte Desert. We estimated plant biomass and fitness through different variables such as plant size (diameter x height of the plant), reproductive effort (% flowering or fruiting branches) and percentage of viable seeds (seed set). We observed that browsing decreased plant biomass and fitness, both through reproductive effort and seed set. However, the successional types of species showed different seed set in response to grazing intensity. With increased stocking density, the size of early species decreased, the size of intermediate species increased and the size of late species did not show significant changes. In general, browsing negatively affected the reproductive effort of all species, and the seed set only in late specie, while early and intermediate species showed an increase in seed set. These results suggest that late species are the most affected by livestock in terms of fecundity, which might reduce their recruitment. The increase in their biomass with stocking density in intermediate species suggests a compensatory response, which could give them a short-term advantage. Tissue loss suffered by plants due to livestock consumption impacts the seed set, with possible consequences on the rate and time of seedling emergence. These results aid to understand plant population dynamics under disturbances, providing useful information to elaborate adequate conservation, sustainable management and restoration strategies for arid ecosystems.

Density-dependent effects on the reproductive outcome of a native tree at tropical restored habitats

Plants are involved in different interactions with animals that may have contrasting effects on their reproductive output. However, as multitrophic interactions are resource-mediated and density-dependent, the frequency at which these interactions occur is modulated by the demographical characteristics of the populations of interacting species. For example, while plant aggregation may increase pollinator attraction and consequently, pollination success, an increased seed set may also attract more seed predators. Therefore, the intensity of pollination and seed predation events may affect plant population dynamics. Although multitrophic plant-animal interactions are crucial for maintaining biodiversity in terrestrial ecosystems, they have seldom been studied together, especially in restored habitats. To fill this gap, we used five restoration sites that used Inga vera trees at different densities to evaluate how density-dependent effects impact fruit set, seed predation, seed germination rate and the number of viable germinated seeds (i.e., the net effect of pollination and seed predation). Using structural equation models to assess the isolated effects of each predictor variable in each response variable and the cascading effects of each response variable on another, we found that density-dependent effects influenced I. vera reproduction. While I. vera trees in high density presented higher fruit set and seed predation rates, trees in low-density plantations presented lower fruit set, but seed predators consumed fewer seeds. The contrasting results of final seed germination rates revealed that density-dependent effects are pivotal to plant establishment and population dynamics. We argue that the study of density-dependent multitrophic plant-animal interactions is essential to guarantee that the efforts done in restoration initiatives can turn into successful results in terms of restoring ecosystem structure and stability.

Soil Seed Bank of Alien and Native Cornus (Cornaceae) Taxa in Lithuania: What Determines Seed Density and Vertical Distribution in Soil?

Soil seed banks of alien plant species are sources of propagules that play a crucial role in plant population dynamics. Studies on seed banks of woody alien species are crucial for understanding mechanisms of their encroachment on natural habitats. This study aimed to compare vertical distribution, density and composition of seed banks formed by native Cornus sanguinea subsp. sanguinea and alien C. alba, C. sericea and C. sanguinea subsp. australis in the Southern Hemiboreal zone of Europe. Five sites for each of four taxa were selected for the study, and seeds were sampled using the soil core method (400 samples in two soil layers: the upper, 0–5 cm, and the lower, 5–10 cm). Extracted seeds were tested with tetrazolium chloride stain to assess their viability. Differences in the seed banks among taxa were compared using generalised linear mixed models (GLMM). The GLMM analysis revealed significant differences in soil seed bank densities in the upper soil between the studied taxa (p < 0.001). We found that two of the alien taxa (C. alba and C. sanguinea subsp. australis) formed a much denser seed bank containing more viable seeds than the native Cornus sanguinea subsp. sanguinea. All three alien species contained more viable seeds (from 40.7% to 45.2% in the upper soil layer) than the native C. sanguinea subsp. sanguinea (19.4% in the upper and 18.2% in the lower soil layer). The cover of Cornus and habitat type had no significant effect on the density of the seed bank, according to GLMM. This study supports the hypothesis that seed banks of alien C. alba and C. sanguinea subsp. australis are denser than those of native C. sanguinea subsp. sanguinea. Furthermore, the seed bank of alien taxa contained more viable seeds than the seed bank of C. sanguinea subsp. sanguinea. Results of this study contribute to the understanding of the invasiveness of alien Cornus taxa.

Climate influence on plant-pollinator interactions in the keystone species Vaccinium myrtillus.

Climate change is altering the world's ecosystems through direct effects of climate warming and precipitation changes but also indirectly through changes in biotic interactions. For instance, climate‐driven changes in plant and/or insect communities may alter plant–pollinator interactions, thereby influencing plant reproductive success and ultimately population dynamics of insect‐pollinated plants. To better understand how the importance of insect pollination for plant fruit set varies with climate, we experimentally excluded pollinators from the partly selfing keystone species Vaccinium myrtillus along elevational gradients in the forest‐tundra ecotone in central Norway. The study comprised three mountain areas, seven elevational gradients spanning from the climatically relatively benign birch forest to the colder alpine areas above the tree line, and 180 plots of 1 × 1 m, with experimental treatments allocated randomly to plots within sites. Within the experimental plots, we counted the number of flowers of V. myrtillus and counted and weighed all fruits, as well as seeds for a selection of fruits. Excluding pollinators resulted in lower fruit production, as well as reduced fruit and seed mass of V. myrtillus. In the alpine sites pollinator exclusion resulted in 84% fewer fruits, 50% lower fruit weight, and 50% lower seed weight compared to control conditions. Contrary to our expectations, the negative effect of pollinator exclusion was less pronounced in the forest compared to alpine sites, suggesting that the importance of insect pollination for seed production is lower at low elevations. Our findings indicate that the keystone species V. myrtillus is relatively robust to changes in the pollinator community in a warmer climate, thereby making it less vulnerable to climate‐driven changes in plant–pollinator interactions.

Comparative impacts of long‐term trends in snowmelt and species interactions on plant population dynamics

Abstract Climate change can impact plant fitness and population persistence directly through changing abiotic conditions and indirectly through its effects on species interactions. Pollination and seed predation are important biotic interactions that can impact plant fitness, but their impact on population growth rates relative to the role of direct climatic effects is unknown. We combined 13 years of experiments on pollen limitation of seed set and pre‐dispersal seed predation in Ipomopsis aggregata, a subalpine wildflower, with a long‐term demographic study that has documented declining population growth with earlier spring snowmelt date. We determined how pollen limitation and seed predation changed with snowmelt date over 21 years and incorporated those effects into an integral projection model to assess relative impacts of biotic factors on population growth. Both pollen limitation and the difference in stigma pollen load between pollen‐supplemented and control plants declined over years. Neither pollen limitation nor seed predation changed detectably with snowmelt date, suggesting an absence of indirect effects of that specific abiotic factor on these indices of biotic interactions. The projected biotic impacts of pollen limitation and seed predation on population growth rate were small compared to factors associated with snowmelt date. Providing full pollination would delay the projected date when earlier snowmelt will cause populations to fall below replacement by only 14 years. Synthesis. Full pollination and elimination of seed predation would not compensate for the strong detrimental effects of early snowmelt on population growth rate, which in I. aggregata appears driven largely by abiotic environmental factors. The reduction over two decades in pollen limitation also suggests that natural selection on floral traits may weaken with continued climate change. These results highlight the value of studying both abiotic factors and biotic interactions to understand how climate change will influence plant populations.

Cover and density of southwestern ponderosa pine understory plants in permanent chart quadrats (2002-2020).

This data set consists of 101 permanent 1m × 1m (1-m2 ) quadrats located within southwestern ponderosa pine ecosystems near Flagstaff, Arizona, USA. Individual plants in these quadrats were identified and mapped annually for 19 years (2002-2020). The original chart quadrats were established between 1912 and 1927 to determine the effects of domestic livestock grazing on herbaceous plants and pine seedlings. Today these data provide opportunities to examine the effects of climate and land-use change on plant demography, population dynamics, and community processes. We provide the following data and data formats: (1) digitized maps of all plant locations in shapefile and geodatabase format, (2) shapefiles showing annual locations of each individual plant species, (3) annual maps of each quadrat in TIFF and PDF format, (4) annual basal area of each species per quadrat for species mapped as polygons, (5) tabular representation of polygon areas and centroid locations for plant species mapped as polygons, (6) tabular representation of point locations for plant species mapped as points, (7) plot-scale 20 m × 20 m overstory tree canopy cover, tree basal area, parent material, and elevation, (8) quadrat-scale information (e.g., quadrat site and number, coordinates in UTM Zone 12 and latitude/longitude, and descriptive comments for each quadrat), (9) plant species list, (10) summary of plant species observed in each quadrat, (11) summary of quadrats mapped by site and year, and (12) data formatted for use in Integral Projection Models (IPM) and plant population analyses. There are no copyright restrictions; please cite this paper and the associated data set when data are used in publications.

Quantifying cardinal temperatures and thermal time for seed germination of Papaver dubium and P. rhoeas

ABSTRACT Background Temperature plays a key role in plants distribution. Cardinal temperatures are important parameters for plant population dynamics models. Aims This study was conducted to estimate the cardinal temperatures and other parameters in relation to temperature using three non-linear regression models (segmented, dent-like and beta) to project the germination rate and temperature relation of Papaver dubium and P. rhoeas. Methods An optimisation method was used to fit the models and their statistical parameters. Their efficiency was compared with the coefficient of determination (R2), root mean square error (RMSE) and the Akaike Information Criterion. Results Calculated cardinal temperatures differed for different germination percentiles (10, 30, 50%). The time required to 50% germination of both P. dubium and P. rhoaes was more accurate than the time required to 10% and 30% germination between observed and predicted values. According to the outputs of the segmented model, base, optimum and maximum temperatures of P. rhoeas were 1.9°C, 22.4°C and 39.6°C, respectively. The corresponding values for P. dubium were 2.1°C, 22.1°C and 39.1°C. Conclusions The parameters related to temperature provide the basic information to determine the time needed for germination and to project potentially suitable areas for invasion. The segmented model is appropriate for the estimation of the cardinal temperatures of both Papaver species.

Woody plant decline in the Sahel of western Niger (1996–2017):is it driven by climate or land use changes?

Although a recovery of woody vegetation has been observed throughout the Sahel, western Niger has not followed the overall satellite-derived greening trend. While satellite imagery can be used to study overall patterns and trends, only field observations can provide insights in the dynamics of woody plant populations. Here we used field data from 29 sites in the Dantiandou district in Niger to study woody species composition, plant density, crown cover, basal area, foliage and wood mass from 1996 to 2017. All sites show a decrease in woody plant parameters with a faster decrease in rangeland than in agricultural land. Most of the decrease is due to the loss of shrubs, while trees do not change significantly. When field observations were scaled up to the district level using land use maps, shrub density decreased from 342 to 155 ha−1 in agricultural land, and from 1567 to 250 ha−1 in rangeland. Trends in annual rainfall and soil moisture during the study period were not significant and cannot explain the decrease of woody vegetation. Instead, the expansion of cropped areas, shortened crop-fallow cycles and increasing pressure on wood resources to satisfy demand for fuel and construction materials may have contributed to the decline.

Occupancy times for time-dependent stage-structured models

During their lifetimes, individuals in populations pass through different states, and the notion of an occupancy time describes the amount of time an individual spends in a given set of states. Questions related to this idea were studied in a recent paper by Roth and Caswell for cases where the environmental conditions are constant. However, it is truly important to consider the case where environments are changing randomly or in directional way through time, so the transition probabilities between different states change over time, motivating the use of time-dependent stage-structured models. Using absorbing inhomogenous Markov chains and the discrete-time McKendrick–von Foerster equation, we derive explicit formulas for the occupancy time, its expectation, and its higher-order moments for stage-structured models with time-dependent transition rates. The results provide insights into the dynamics of long lived plant or animal populations where individuals transition in both directions between reproductive and non reproductive stages. We apply our approach to study a specific time-dependent model of the Southern Fulmar, and obtain insights into how the number of breeding attempts depends on external conditions that vary through time.

Cereal Husks: Versatile Roles in Grain Quality and Seedling Performance

The seed is the fundamental unit of the dispersal of dry, dehiscent fruits, in which the fruit splits open at maturity to allow for seed dispersal. However, dry fruits may be indehiscent and therefore represent the dispersal unit (DU). Cereals possess a one-seeded fruit, whereby the seed coat and the fruit coat are fused together to generate the caryopsis. This caryopsis may be covered by floral bracts to generate two types of DUs, namely florets, whereby the caryopsis is enclosed by the lemma and the palea (e.g., Avenasterilis) or spikelet, whereby the floret(s) is further covered by the glumes (Triticum turgidum var. dicoccoides). Here, we highlight the dead coverings enclosing the caryopsis in cereals, namely the husks as an integral component of the dispersal unit that play multifaceted roles in grain biology. Thus, besides protection and dispersal means, the husks function as a rich maternal supply of proteins and metabolites for enhancing growth and development, combat potential pathogens as well as confer tolerance to abiotic stresses. These attributes might have broad implications for crop performance, plant population dynamics and diversity in ecological systems, and for conservation of genetic resources in seed banks.

Dormancy and viability ofFerocactus peninsulae(Cactaceae) seeds

AbstractKnowledge on seed dormancy is crucial for the understanding of plant population dynamics, as it controls seed germination and seed bank formation. Dormant seeds have high potential to establish in soil seed banks, but such information within Cactaceae is scarce, although it is essential for conservation programs. The aim of this study was to determine if seeds ofFerocactus peninsulaeshowed any kind of dormancy and to test their germination capacity after storage. This was assessed with 15 seed sowing experiments done over 4 years with seeds stored under room conditions (20 ± 2°C). We demonstrated the existence of physiological dormancy inF. peninsulaeseeds that is broken with an after‐ripening period. Germination was low during the first 3 months of storage (d = 0.206) but increased after 10 months of storage (d = 0.654), and seeds maintained their viability at 48 months (d = 0.707). Also, their speed of germination increased with storage time.Ferocactus peninsulaeseeds are positively photoblastic, and the requirement for light for germination persisted over all experiments. The results provide crucial information for propagation and conservation research and may allow us to infer thatF. peninsulaeseeds are able to form a persistent soil seed bank, as they maintained their viability after dormancy is released.

Effects of Different Soils on the Biomass and Photosynthesis of Rumex nepalensis in Subalpine Region of Southwestern China

The performance of Rumex nepalensis, an important medicinal herb, varies significantly among subalpine grasslands, shrublands and forest ecosystems in southwestern China. Plant–soil feedback is receiving increasing interest as an important driver influencing plant growth and population dynamics. However, the feedback effects of soils from different ecosystems on R. nepalensis remain poorly understood. A greenhouse experiment was carried out to identify the effects of different soil sources on the photosynthesis and biomass of R. nepalensis. R. nepalensis was grown in soils collected from the rooting zones of R. nepalensis (a grassland soil, RS treatment), Hippophae rhamnoides (a shrub soil, HS treatment), and Picea asperata (a forest soil, PS treatment). The chlorophyll contents, net photosynthetic rates, and biomasses of R. nepalensis differed significantly among the three soils and followed the order of RS > HS > PS. After soil sterilization, these plant parameters followed the order of RS > PS > HS. The total biomass was 16.5 times higher in sterilized PS than in unsterilized PS, indicating that the existence of soil microbes in P. asperata forest ecosystems could strongly inhibit R. nepalensis growth. The root to shoot biomass ratio of R. nepalensis was the highest in the sterilized PS but the lowest in the unsterilized PS, which showed that soil microbes in PS could change the biomass allocation. Constrained redundancy analysis and path analysis suggested that soil microbes could impact the growth of R. nepalensis via the activities of soil extracellular enzymes (e.g., β-1,4-N-acetylglucosaminidase (NAG)) in live soils. The soil total soluble nitrogen concentration might be the main soil factor regulating R. nepalensis performance in sterilized soils. Our findings underline the importance of the soil microbes and nitrogen to R. nepalensis performance in natural ecosystems and will help to better predict plant population dynamics.

滨海湿地植物种群Allee效应驱动机制研究进展

Allee效应是指生物个体适应度与种群规模或密度之间呈正向关联的现象, 因与植物种群动态和种群灭绝密切相关而受到生态学家的普遍重视。阐释多重胁迫下滨海湿地植物种群响应机制, 从保护生物多样性和维持生态系统稳定性层面发展系统性生态修复措施成为相关研究关注的重点。本研究分别从遗传过程、花粉扩散过程和生物互作关系不同层面, 总结分析了植物种群Allee效应驱动机制的研究进展。一方面, 植物因遗传过程中近交衰退、遗传变异丧失、有害突变累积等遗传结构改变造成繁殖失败而引发Allee效应；另一方面, 植物花粉扩散过程和动植物互作关系影响下的花粉限制也通过影响植物种群繁殖力成为驱动Allee效应的关键因素。滨海湿地水盐梯度变异及格局破碎化影响下, 植物种群遭受Allee效应的风险需引起关注, 维持滨海湿地植物种群适宜分布格局和生物连通过程成为缓解Allee效应的重要手段。结合生理学与化学生态学研究手段和长时间尺度动态监测技术, 有助于进一步阐释环境及生物等多重胁迫下Allee效应的非线性驱动机制。;Allee effect, the positive association between individual fitness and population size or density, has attracted more attentions from ecologists because of its closely relationship with plant population dynamics and population extinction. By explaining Allee effect of plant population under multiple stresses, developing systematic ecological restoration measures based on the biodiversity protection and ecosystem stability has become the focus of relevant research. This study systematically summarized the research results of different driving mechanisms of Allee effect in plant population in coastal wetlands based on genetic process, pollen dispersal process and plant-pollinator interaction. On the one hand, Allee effect was driven by reproductive failure due to genetic structure changes, such as inbreeding depression, genetic variation loss, and harmful mutations accumulation in the genetic process. On the other hand, Allee effect was caused by changes in plant population fecundity due to pollen limitation, which was affected by pollen dispersal process and plant-pollinator interaction. In the context of water and salt gradient variation and pattern fragmentation in coastal wetlands, it is conspicuous for the risk of Allee effect on plant population. It is important for alleviating Allee effect of plant population in coastal wetlands through providing suitable habitat, ensuring biological connectivity, and constructing population patches. Combination of physiological and chemical ecological research methods as well as long-term dynamic monitoring will help to further explain the nonlinear driving mechanism of Allee effect under multiple environmental and biological stresses.

Contribuição do Programa BIOTA/FAPESP para o conhecimento sobre polinização e reprodução em plantas

Abstract Interactions between plant and pollinators are associated with the origin and maintenance of species diversity, as well as ecosystem functioning. The potential of pollination as an ecosystem service is evidenced by its association with food production. Understanding pollination at the landscape scale is essential for characterizing the pollination service for several crops that depend on pollinators for fruit and seed set that make up the human diet. Our aim was to carry out a literature review of studies and projects funded by BIOTA/FAPESP to illustrate the main research approaches developed in the field of Pollination Biology, especially related to plant-pollinator interactions. Plant-pollinator interactions in the Atlantic forest were leveraged as a result of this long-term research program, during which several papers were published in international journals. Pollination by bees (melittophily) was the most representative pollination system studied. In addition to melittophily, other interactions were studied such as pollination by hawkmoths (sphingophily), by hummingbirds (ornithophily) and by bats (chiropterophily). The specific mutualistic relationships between fig trees and fig wasps were also subject of studies within the Program. At the beginning of the BIOTA/FAPESP Program, there were many gaps in basic information about pollination and breeding systems of Brazilian native plant species. Thus, the Program was fundamental to fuel research on the natural history of plants and pollinators from the Atlantic forest. Overall, the Program funded studies that investigated themes such as functional pollination ecology, pollinator effectiveness, plant population genetics, structure and dynamics of plant-pollinator interaction networks, as well as geographic distribution and macroevolution of pollination systems, as well as genetic and molecular studies of native plant populations focusing on pollen flow and genetic structure of populations. Additionally, studies on pollination in the context of landscape ecology had the aim of assessing the effects of forest fragmentation on the functioning of plant populations and their interactions with pollinators and the relationships between landscape structure and ecological processes, biodiversity, and ecosystem service. Therefore, the Program had a prominent role in producing basic data with great implications for understanding the ecology and promoting the conservation of plant-pollinator interactions.

A Review of Research and Developments with Insect Agents Used for Biological Control of Australian Acacia Species (Caesalpinioideae) in South Africa

There are 14 species of Australian Acacia now known to be invasive in South Africa, ten of which are under some form of biological control (biocontrol). The biocontrol agents introduced against this group include a fungal pathogen, Uromycladium morrisii Doungsa-ard, McTaggart, Geering & R.G. Shivas (Pucciniales: Raveneliaceae) for Acacia saligna (Labill.) H.L.Wendl., and ten insect species, including two bud-galling wasps, five seed-feeding weevils and three flower-galling fly species, all of which supress reproductive output of their hosts. There are also two native fungal pathogens that have become associated with the introduced acacias, and which have been developed for potential mycoherbicide use. Screening and importation of new agents has seen limited activity in the ten-year period reviewed here (i.e., 2011–2020). Most attention has been focussed on efforts to evaluate the effectiveness of the established agents and, importantly, to gain an understanding of the role of seeds in the population dynamics of the host plants.