Plant Ecology最新文献

Species distribution modelling remains a valuable tool for managing conservation practices for medicinal plants. As climate change threatens the planet’s biodiversity, it has become imperative to investigate its impact on our important bioresources. We studied the distribution of two medicinally essential orchid taxa, Crepidium acuminatum and Satyrium nepalense, in the Darjeeling Himalayan region using MaxEnt modelling. AUC (Area Under the Curve) and the TSS (True Skill Statistic) value for the models was calculated to gauge model performance. The models generated via MaxEnt performed excellently with > 0.9 AUC value and 0.6 to > 0.85 TSS value. The most influential factor affecting the distribution of C. acuminatum seems to be precipitation, whilst the factor affecting S. nepalense is altitude. The current potential habitat of C. acuminatum and S. nepalense was 385.25 km² (12.51%) and 245.25 km² (7.96%), respectively. Of the total current potential habitat, only 108.75 km² (3.53%) and 61.5 km² (2.0%) were of good habitat suitability for C. acuminatum and S. nepalense, respectively. Similarly, only 100.5 km² (3.26%) and 43.5 km² (1.41%) were of excellent habitat suitability for C. acuminatum and S. nepalense, respectively. Hence, Maxent identified highly suitable regions for the conservation of both species. The model predicts that for C. acuminatum, the total suitable habitat may decrease by as much as 113.25 km^2. In contrast, for S. nepalense, the total suitable habitat may increase by as much as 230.25 km² in future scenarios. However, when suitable habitat increases in certain regions for both species, the habitat is usually of poor suitability. This reflects the strong effect of climate change on the future of medicinal plants, particularly orchids. Hence, this indicates the need for better monitoring and holistic conservation strategies.

Flower colour is a fascinating trait that has been of interest to biologists for its utility in understanding variation in natural populations and its role in floral evolution. Here, we investigated whether the co-occurring white and pink flowers of individual plants of the Drakensberg near-endemic taxon, Rhodohypoxis baurii (Baker) Nel. var. confecta Hilliard & Burtt (Hypoxidaceae) are an example of phenotypic plasticity or of flower colour polymorphism and what environmental factors may drive observed changes. We used both field and growth chamber studies to test the relationship between environmental variables and the shift in the proportion of the two flower colours over the flowering season. We found that single flowers do not change colour over time, but some individual plants are potentially responding to changes in environmental conditions by producing pigmented flowers later in the flowering season, which suggests that the trait could be plastic rather than a true polymorphism. The field data showed that soil moisture along with an interaction between ultraviolet (UV) radiation and temperature best explained the change in the number of pigmented flowers over the flowering season but none of our treatments in the growth chambers had a significant effect on the change in the number of pigmented flowers. Given the relationship between anthocyanin production and environmental stress, our field findings suggest that soil moisture plays an important role in facilitating stress tolerance and that R. baurii var. confecta may produce anthocyanins to prevent tissue damage from increased temperature and UV later in the flowering season.

Medicago citrina and Euphorbia margalidiana are two microinsular species from the Western Mediterranean which are amongst the top 50 most threatened species of the Mediterranean. Conservation plans for both taxa involve translocation and ex situ seedling growth, yet salinity tolerance remains unknown for both species. The main objective of this work was to analyse how germination is modulated by salinity and to evaluate the seed buoyancy of both species to give light to their sea-dispersal capabilities. Salinity tolerance tests were performed using increasing concentrations (100, 200, 300, and 400 mM) solutions of different salts (NaCl, MgCl₂, MgSO₄, and Na₂SO₄). Recovery tests were carried out to analyse the potential ionic toxicity of salts. Seed buoyancy was also evaluated in sea and distilled water for each species. M. citrina was the most salt tolerant, germinating at values below 35.6 mS/cm, whilst E. margalidiana only germinated below 21.4 mS/cm. Na₂SO₄ and MgCl₂ are the salts with the strongest inhibitory effect, whilst MgSO4 is the least inhibitory salt. In both species, buoyancy is very limited, being higher in M. citrina (up to 15 days) compared to E. margalidiana (4 days). The higher salinity tolerance and buoyancy allows M. citrina to colonise a broader range of islets than E. margalidiana, which requires moderate altitudes to keep populations away from salt impact. Both species cannot be considered as halophytes and so in situ and ex situ conservation measures should be carried out avoiding high salinity areas to ensure seedling development.

Agave reproduction can occur both sexually and asexually; however, the vast majority of species mainly propagate asexually. Seed germination studies are of great importance in conservation biology, ecological restoration, and the development of management plans. Our aim was to determine the effect of the crossing system and storage time on the germination success in seeds of Agave obscura (Agavaceae), a species endemic to Mexico. The seeds were derived from manual cross-pollination, manual self-pollination, and natural pollination, and had been stored for 19 and seven months. Germination experiments were conducted under controlled light conditions at 25 °C. The percentage of germination in seeds stored for seven months (76%) was higher than in those stored for 19 months (46%) (df = 1, dev.resid = 1439.6, Pr (> chi) = < 0.05)) Crossing systems show effects in the percentage of germination (P(> │Chi │ < 0.05). The seed germination capacity decreased as a function of storage time. Seed storage time had no effect on subsequent seedling size, but pollination type did affect seedling growth. A. obscura produces viable seeds with germination capacity in a natural manner, which favors the maintenance of natural populations, although it’s necessary to evaluate other ecological processes such as the establishment of seedlings in the field and their survival in different age categories.

Plants have the ability to recognize their kin neighbors, which may be a beneficial trait that increases inclusive fitness, by suppressing individual growth to support the combined growth of the group. However, the advantages of kin cooperation (known as kin selection theory), may differ across environmental gradients, with competition between related individuals potentially being detrimental under resource limitation (following niche partitioning theory). The study aimed to understand how quinoa (Chenopodium quinoa (Willd)) plants grow with kin or with non-kin under different nutrient supply rates. Plants were grown in treatments’ post-germination for 70 days. Biomass accumulation, allocation to organs, and organ traits related to resource acquisition were measured at the end of the experiment. Total mass and shoot mass were greater for plants grown with kin than with non-kin across nutrient treatments. Plants grown with kin had greater root allocation than with non-kin under low and high nutrients. Allocation to leaves, specific leaf area, and average leaf mass were greater for plants grown with non-kin than kin under high-nutrient supply, but did not differ under low-nutrient supply. Allocation to stem was greater for plants grown with kin than non-kin under high-nutrient supply, but did not differ under low-nutrient supply. Specific taproot length and specific stem length were respectively positively and negatively related to increased fertility, but unrelated to kinship. Our results suggest that both niche partitioning and kin selection processes may be at play in quinoa, depending on whether soil nutrient competition is more important. Under both situations, quinoa plants always grew better with kin than non-kin regardless of soil nutrient conditions.

Abstract

Understanding the interactive relationships between organisms is key to understanding community structure and planning appropriate conservation measures. Even more so for plant-plant interactions, which are poorly understood. We studied the vascular epiphyte community and its interactions with the tree community (phorophytes) in Amazonian black-water floodplain forests (igapó), analyzing 58 floristic inventory plots located along a 517 km stretch of the Brazilian Negro River, in the Central Amazon. The vascular epiphytes and trees were identified and quantified, and the physical attributes of the bark were measured, as well as the diameter at breast height (DBH) of the tree species. A total of 2746 trees ≥ 10 cm DBH were inventoried, of which 969 were phorophytes (35.29%), hosting 4692 individuals of epiphytic species, belonging to 17 families 50 genera, and 106 species. Pouteria elegans was the most abundant phorophyte, however, Aldina latifolia showed proportionally higher richness and abundance of epiphytes. Codonanthopsis crassifolia was the epiphyte that colonized most of the phorophytes and showed the highest Epiphytic Importance Value (EIV). The average values for thickness, saturated weight, water retention capacity, and diameter were significantly higher in the tree species that housed vascular epiphytes. In addition, the vascular epiphyte richness (R²m = 0.32; R²c = 0.41) and abundance (R²m = 0.36; R²c = 0.90) were strongly influenced by larger diameters of phorophytes and their saturated bark weight. Our results confirm the importance of phorophyte size (DBH) for epiphyte colonization, present the most complete epiphyte list of Amazonian black-water floodplain forests and provide evidence that physical attributes of tree bark drive the structure of vascular epiphyte-phorophyte interactions.

Abstract

Invasive plants can negatively impact native plant communities through indirect apparent competition driven by altered habitat structure for herbivores and seed predators. The annual invasive grass Microstegium vimineum greatly increases ground-level understory vegetative cover in US eastern deciduous forests, potentially altering foraging patterns by small mammals, which in turn could increase seed consumption of native plant species by mammals that take advantage of increased cover. To test this, we conducted a seed predation study using pans containing small and large native seeds placed in uninvaded and Microstegium-invaded habitats across four seasons. Counter to our predictions, we found that seed removal was 19% higher in uninvaded areas than Microstegium-invaded areas. While our results may be initially interpreted as positive for native species, reductions in small mammal seed foraging could also reduce scatterhoarding of large-seeded tree species, negatively impacting forest regeneration.

Conspecific negative density dependence (CNDD) is one of the processes that can maintain high species diversity by decreasing population growth rates at high densities, and can thereby favour locally less common species over common ones. But the methods for detection of CNDD can produce false signals, in particular, overestimate CNDD, due to error prone predictors causing regression dilution and underestimation of regression slope. Using simulated and real observed data from tropical forest plot in Barro Colorado Island, we showed that major axis regression can considerably decrease the effects of errors in predictors where classical regression methods did not succeed. The best major axis method correctly identified (1) 93% of no CNDD cases in simulated data, and (2) no CNDD in real species observed data in concordance with direct assessment using survival between censuses. The errors were mostly higher if artificial/virtual adults were introduced in the quadrats with saplings, but without adults. Although major axis methods can be used as a simple remedy for the reductions of these biases, to properly identify dynamic processes like CNDD, repeated census of the plot and identification of parent’s offspring still provide the most relevant data.