Within-generation and transgenerational plasticity in growth and regeneration of a subordinate annual grass in a rainfall experiment

Aridity Gradients Shape Intraspecific Variability of Morphological Traits in Native Ceratonia siliqua L. of Morocco

The carob tree (Ceratonia siliqua L.) is a significant fruit tree in the Mediterranean region with cultural, biological, and ecological importance. Despite its importance, intraspecific trait variability (ITV) in carob trees has been largely overlooked in previous studies. Understanding ITV and its relationship with environmental conditions is crucial for conservation and breeding programs. In this study, we investigated the variability of carob pod and seed-related traits across different ecological scales in 25 studied populations in Morocco. Significant differences in morphological traits were observed between carob populations at various ecological levels, and pod-related traits exhibited greater variability than seed traits. Correlation analysis revealed strong associations between carob morphological traits and environmental conditions, with altitude and aridity index playing an influential role. The aridity gradient was strongly related to changes in pod size, seed number, and size, as well as seed yield. Our findings highlight an important ITV reaching 45% at the intra-population level, 36.5% at the inter-geographic level, and 30% at the inter-population level. Overall, this study contributes valuable insights into the ecology and adaptation of carob trees, emphasizing the importance of considering intraspecific variability when studying this remarkable species. This knowledge is critical for addressing the challenges posed by climate change and human activities on the long-term survival and ecological functioning of carob populations.

Seed Coat Morphology and Sculpturing of Selected Invasive Alien Plants from Lesser Himalaya Pakistan and Their Systematic Implications

Invasive alien species (IAS) are considered as the second major threat to biodiversity after habitat destruction worldwide. They are aggressive competitors and dominate an ecosystem where they introduce and cause reduction in indigenous diversity. Invasive plants alter the evolutionary pathways of native species by competition, niche displacement, hybridization, introgression, predation, and ultimately extinction of native species. Biological invasion also results in economic and environmental damage and harm to human health. Invasive plants have an effective reproductive as well as dispersal mechanisms. Most invasive plants produce abundant fruits and seeds that are widely disseminated and remain viable in the soil for several years. Invasive plants may change their seed character in order to adapt themselves to the new environment and facilitate their performance. A study on seed coat sculpturing in invasive alien plants collected from Lesser Himalaya region, Pakistan, was conducted using scanning electron microscope to determine the importance of seed morphological characters as an additional tool for identification. Quantitative characters such as seed length and width, macromorphological characters including color, hilum position, and seed shape, and micromorphological characters of seed including surface patterns and periclinal and anticlinal wall of seeds were studied. Findings at the present indicate that most of the seeds were found spherical followed by ovate and elliptical in shape with smooth surface and showed terminal hilum. Almost reticulate seed patterns were observed in seeds. Majority of seeds showed raised anticlinal walls with protuberance periclinal walls. The seeds of Xanthium strumarium were observed with maximum length of 13 mm and with width of 8 mm. Length by width ratio of seeds was also calculated; it was found that maximum L/W ratio was observed in Sonchus oleraceus L., i.e., 2.66. Seed characters, both macro- and micromorphological, furnish useful data for classification and delimitation of invasive taxa. This study will help to understand the invasion mechanism in plants due to variations in seed surface, shape, and other characters. Adaptive behavior of the seed during the invasion process of the new ecosystem is also elaborated.

Latitudinal and Longitudinal Trends of Seed Traits Indicate Adaptive Strategies of an Invasive Plant

Invasive plants may change their seed traits to adapt to the environment and facilitate their performance. Studies on variation in seed traits among populations of an invader along latitudes/longitudes may assist in revealing how invasive plants cope with variable climates. In this study, we collected seeds of 26 populations of the global invasive plant Ambrosia artemisiifolia along ranges spanning 23° latitudes and 20° longitudes that are highly correlated in its invasive range in China. We measured over 20 seed traits, including seed morphology, phytohormone, nutrients, and germination, and investigated how the climate along the latitudes affects those traits. We found that germination time was significantly delayed with increasing latitude and longitude, while the reversed patterns were true for the germination rate. From low to high latitude, seed size, abscisic acid, and fatty acid were increased, likely affecting seed germination. Our analysis further demonstrated that temperature is the dominant driver of the variability in seed traits and germination. Germination rates of larger seeds in cold ranges were lower, while smaller seeds from warm ranges germinated faster, likely indicating adaptive strategies of the invasive plant in seed trait functional ecology. Together, our findings provide new insights into understanding the seed adaptation strategies during the invasion process and the underlying physiological and biochemical mechanisms involved.

Experimental drought indirectly enhances the individual performance and the abundance of an invasive annual weed

During environmental change, invasive species may be favored by increased resource input or reduced resource use of the resident community. Plasticity in certain plant traits of invasive species may be one possible mechanism behind their ability to quickly exploit unused resources. We tested whether rainfall manipulations (severe drought, moderate drought, watering) alter the growth and reproductive success of the invasive annual Conyza canadensis, and if it translates into a change in the abundance of the species in a semiarid perennial grassland in Central Hungary. Overall, C. canadensis exhibited greater individual performance and higher abundance in drought plots than in control and watered plots. At individual level, plants showed the strongest response to moderate drought: they grew 2.5-times taller than in control and watered plots, and produced twice and 2.5-times more seeds than in watered and control plots, respectively. Reproductive phenology was advanced in response to rain exclusions. Although severe drought caused 40% mortality, the cumulative performance of C. canadensis, expressed as plot-level aboveground biomass, was consistently greater in severe drought plots than in control and watered plots throughout the 3 years of the study. The higher performance of C. canadensis in drought plots is most likely due to the decreased abundance and, thus, decreased competitive effect of previously dominant perennial grasses caused by the rain exclusions. We conclude that drier summers that suppress perennial grasses will favor this alien annual forb, and phenotypic plasticity in growth and reproduction may contribute to its invasion success.

Life history response of Echinops gmelinii Turcz. to variation in the rainfall pattern in a temperate desert

BACKGROUND

Current and future changes in rainfall amount and frequency may particularly impact annual plants in desert ecosystems. The winter annual Echinops gmelinii Turcz. is widely distributed in the desert habitats of northern China and is a dominant pioneer annual plant following sand stabilization in the Tengger Desert. This species plays a vital role in dune stabilization during spring and early summer, when wind erosion is the most severe and frequent. However, seedling emergence and regeneration in sandy soil are mainly determined by rainfall patterns. Therefore, understanding the life history response of this species to rainfall variation is necessary for understanding the change of population dynamics under the future climate change.

METHODS

A field simulation rainfall pot experiment using rainout shelter was conducted that included five amounts and five frequencies of rainfall based on historical and predicted values to monitor the life history responses of E. gmelinii in a near-natural habitat.

RESULTS

We found that rainfall amount and frequency significantly affected seedling survival, growth and reproduction. The plant height, biomass, capitula number, seed number, seed mass and reproductive effort, but not the root/shoot ratio, significantly increased with increasing rainfall. Further, these traits exhibited the greatest response to low-frequency and larger rainfall events, especially the optimal rainfall frequency of 10-day intervals. Offspring seed germination showed increasing trends with decreasing rainfall, suggesting that the maternal effects may have occurred.

CONCLUSIONS

Our study shows that the plasticity in growth and reproduction of E. gmelinii in response to rainfall variations may help it to gain dominance in the harsh and unpredictable desert environment. Furthermore, population development of this winter annual species should be promoted under the likely future scenarios of large rainfall events and increasing cool-season precipitation in temperate desert.