Does pollen limitation limit plant ranges? Evidence and implications

Range limits often involve declines in sexual reproduction, reducing fitness, dispersal, and adaptive potential at range edges. For plants, sexual reproduction is frequently limited by inadequate pollination. While case studies show that pollen limitation can limit plant distributions, the extent to which pollination commonly declines toward plant range edges is unknown. Here, we leverage global databases of pollen-supplementation experiments and plant occurrence data to test whether pollen limitation increases toward plant range edges, using a phylogenetically controlled meta-analysis. While there was significant pollen limitation across studies, we found little evidence that pollen limitation increases toward plant range edges. Pollen limitation was not stronger toward the tropics, nor at species' equatorward vs poleward range limits. Meta-analysis results are consistent with results from targeted experiments, in which pollen limitation increased significantly toward only 14% of 14 plant range edges, suggesting that pollination contributes to range limits less often than do other interactions. Together, these results suggest pollination is one of the rich variety of potential ecological factors that can contribute to range limits, rather than a generally important constraint on plant distributions.

Spatially Varying Relationships between Alien Plant Distributions and Environmental Factors in South Korea

Invasive alien plants can severely threaten biodiversity and cause economic losses in the agricultural industry; therefore, identifying the critical environmental factors related to the distribution of alien plants plays a crucial role in ecosystem management. In this study, we applied partial least squares regression (PLSR) and geographically weighted regression (GWR) to estimate the important environmental factors affecting the spread of two invasive and expansive plants, Lactuca scariola L. and Aster pilosus Willd., across South Korea. GWR provides more accurate predictions than ordinary least squares regression, and the local coefficients of GWR allow for the determination of the spatial relationships between alien plant distributions and environmental variables. Based on the model’s results, the distributions of these alien species were significantly associated with anthropogenic effects, such as human population density, residential area, and road density. Furthermore, the two alien species can establish themselves in habitats where native plants cannot thrive, owing to their broad tolerance to temperature and drought conditions. This study suggests that urban development and expansion can facilitate the invasion of these species in metropolitan cities.

Soil plays a pivotal role in the distribution of plants, their traits and ecosystem functions in the French Alps

<p>Experiments and observations have shown that plants and soil biotic and abiotic properties are linked by feedback loops at local scale, in particular because plant functional traits determine the decomposability of the organic matter, which in turn influences the availability of nutrients essential for plant growth. However, the influence of plant-soil linkages on plant distributions and ecosystem functions is understudied at large biogeographic scales.</p><p>Here, I present results of studies along 18 elevational gradients in the French Alps. In a first study, I show how the distributions of 44 plant species does not only depend on climate but also on soil physico-chemical properties and microbial decomposition activity and that plant functional traits play an important role in these distributions. Using hierarchical effects and multi-species distribution models, we found that, in addition to climate, the combination of soil C/N, as a measure of organic matter quality, and exoenzymatic activity, as a measure of microbial decomposition activity, strongly improved predictions of plant distributions. In accordance with the ‘fast-slow’ plant economics spectrum, species with conservative traits performed better under limiting nutrient conditions but were outcompeted by exploitative plants in more favorable environments, resulting in a spatial segregation of plants with different ecological strategies. In a second study, we moved from species to community level to estimate the impact of these plant-soil linkages on ecosystem functions. Using an undirect partial correlation network revealed that the influence of plant traits on the quality of organic matter links aboveground and belowground ecosystem functions. Finally, I show how specific soil trophic groups, notably saprophytic fungi, play key roles in these linkages. This result highlights that decomposition and the organisms involved in this process are the corner stone of ecosystem multifunctionality in nutrient depleted ecosystems such as mountains. Together these results highlight the importance of considering plants and soil biodiversity along with abiotic predictors for better understanding and modelling ecosystem processes and functions in a world where both climatic and soil systems are undergoing profound and rapid transformations.</p>

Asymmetrical pegs in square holes? Functional and phylogenetic determinants of plant community assembly in temperate forest understories

ABSTRACTDespite advances in community assembly theory, uncertainties remain regarding how ecological and evolutionary processes shape species distributions and communities. We analyzed patterns of occurrence for 139 herbaceous plant species across 257 forest stands in Wisconsin (USA) to test predictions from community assembly theory. Specifically, we applied Bayesian phylogenetic linear mixed effects models (PGLMMs) to examine how functional traits and phylogenetic relationships influence plant distributions along environmental gradients and how functional similarity and phylogenetic relatedness affect local species co-occurrence. Leaf height, specific leaf area, and seed mass mediate species distributions along edaphic, climatic, and light gradients. In contrast, functional trait similarity and phylogenetic relationships only weakly affect patterns of local co-occurrence. These results confirm that broad-scale plant distributions are largely shaped by ecological sorting along environmental gradients but suggest deterministic assembly rules based on niche differentiation and complementary resource use may not govern local species co-occurrence in homogeneous environments.Statement of authorshipJB conceived the idea for the study. DL, SJ, and DR collected the vegetation and functional trait data. JB analyzed the data with assistance from DL. KC, KS, TG, and DW secured funding for research and oversaw data collection. JB wrote the first draft of the manuscript, all authors contributed to manuscript revisions.Data accessibility statementUpon acceptance, data will be archived at Figshare (https://figshare.com/) and scripts used to analyze the data will be shared on Github (https://github.com/jaredjbeck/).

Response of Watermelon Pulp (Citrullus colocynthoides) to Intercropped Maize (Zea mays L.) With Plants Distributions Under Different Nitrogen Fertilization Levels

Two field experiments were carried out at the Experimental Farm of Gemmeiza Agriculture Research Station, Agricultural Research Center (ARC), Egypt after 2018 and 2019 summer growing seasons to determine the effect of intercropping pattern of yellow maize hybrid (single cross 168: “SC 168”) with watermelon pulp at three plant distributions (20 cm between hills and one plant/hill, 40 cm between hills and two plants/hill and 60 cm between hills and three plants/hill) and different levels of nitrogen fertilizer (25, 50, 75 and 100% of the recommended dose “120 kg N fad-1”) as well as their interactions on maize and watermelon pulp growth, yield and its attributes as well as competitive relationships and yield advantages. The experiments were carried out in split-plot design with four replicates. The main-plots were assigned to plant distributions of maize, the sub-plots were allocated to levels of nitrogen fertilizer for maize. The obtained results showed that planting maize plants on one side of terraces of 140 cm width with 20 cm between hills and leaving one plant/hill and planting watermelon pulp on the other side of the terraces produced the highest values of plant height, ear height, number of kernels row-1, 100-kernel weight and grain yield fad-1, at the same time the lowest values of ear leaf area, ear length, ear diameter and number of rows ear-1 of maize as well as the lowest values of growth, yield and its attributes of watermelon pulp during the both seasons. Mineral fertilizing maize plants with 75% of the recommended dose (90 kg N/fad) and watermelon pulp with the recommended dose produced the highest values of all studied growth characters, yield and its attributes of maize and watermelon pulp in both seasons. The highest values of land equivalent ratio (LER), relative crowding coefficient (RCC), area time equivalent ratio (ATER), land equivalent coefficient (LEC), aggressivity index (AI), monetary advantage index (MAI), actual yield (L.E.) of watermelon, Total income (L.E.) and economic return (L.E.) were obtained from planting maize plants on one side of terraces of 140 cm width with 60 cm between hills and leaving three plants/hill and planting watermelon pulp on the other side of the terraces besides fertilizing maize plants with 75% of the recommended dose (90 kg N/fad) and watermelon pulp with the recommended dose in both seasons. It can be recommended that planting maize on 60 cm between hills and leaving three plants/hill and planting watermelon pulp on the other side of the terraces besides fertilizing maize plants with 90 kg N/fad and watermelon pulp with the recommended dose to obtain the maximum values growth, yield and its attributes of watermelon pulp and competitive relationships and yield advantages of both crops under the climates conditions of Middle Delta, Egypt.