Aquatic Botany最新文献

Aldrovanda vesiculosa L. (Droseraceae), or waterwheel plant, is a threatened aquatic plant species, and it is quickly vanishing from the natural distribution range in the world. There used to be many localities of the species in Japan, but it was extinct from nature in the country in 1967. The information regarding the localities in Japan was recorded in various sources, but those had not been summarized yet. Therefore, the current study reviewed herbarium specimens and literature, and we documented each location of the species, the dates of discovery and extinction, and the cause of extinction. There were 35 locations, including four artificially introduced sites, in nine prefectures. It was hypothesized that the species had spread due to floods and had been established at each locality. We testified the hypothesis using a simulation map that the plants had spread by floods in the Kanto region, the major distribution area in the country. At the same time, serious floods destroyed some habitats of the species. However, human activities more seriously resulted in habitat loss. The species collected from the localities before the extinction has been under cultivation. Restoration of the habitat and reintroduction of the species has been attempted at a pond, but it is still on the way. The current study has summarized the causes of the extinction of A. vesiculosa in Japan, and it also aims to reduce the potential risk of extinction in extant populations of the species in the world as well as other threatened aquatic plants.

Biodiversity loss is, at present, one of the most severe global environmental issues. However, more demanding species are put at greater risk than generalists. Knowledge of the habitat requirements of threatened species is essential for defining the levels at which nature conservation efforts should prospectively operate. This study describes the habitat niche of the macrophyte species Myriophyllum alterniflorum DC., based on its occurrence along environmental gradients of sediments, flow velocity, turbidity, depth and shade on five brooks of the Upper Palatinate Forest, Bavaria. To examine the transregional validity of our results, we first carried out an analysis on the Pfreimd River and defined the outcomes as a reference. We then defined a transfer system for the other four brooks with M. alterniflorum occurrences, repeated the analysis and compared the results. We found a general pattern of preferred habitat conditions in combination with a regional aspect influencing the species distribution in each brook. We, suggest a broader formulation of habitat characteristics when aiming to describe a transregional pattern. Instead of preferences, we defined local extinction criteria for this species, namely: i) sediment with saprobic fraction, ii) stagnation of flow velocity, iii) strong turbidity iv) shading > 75% and v) water depth > 100 cm. Furthermore, we found that eutrophication is less effective under high-flow conditions. With its high demands on water quality, M. alterniflorum overlaps with the requirements of other endangered species. Therefore, conservation efforts should focus on promoting high-quality habitats, which include sustainable land management approaches at the catchment level.

Nelumbo lutea Wild. (American lotus) has a broad and changing geographical distribution that is influenced by human transplanting and changes to climate, hydrology, and habitat. Populations vary from extensive stands where the species appears to be an effective colonizer, to sites where the species has declined or appears to have been extirpated. Previous studies in apparently stable populations from central and southern United States revealed low genetic diversity within and between populations. In this study, we assess genetic diversity at the northern edge of N. lutea’s range where it is often imperiled. A total of 489 individuals in 25 populations collected in Upper Mississippi River regions in Minnesota and Wisconsin were amplified in 12 microsatellite loci. Ten microsatellite loci indicated significant deviation from Hardy-Weinberg principal and were utilized for further analysis. Generally, genetic diversity was low compared to the genetic studies from southern North America. Despite low levels of genetic differentiation (Fst range; 0.003–0.059), structure and UPGMA analysis indicated the possibility of two distinct clusters and slight admixture in some populations. Initial low genetic diversity in populations was likely caused by founder effect if few individuals were established at each site. Limited migration and clonal growth contribute to the continued low diversity. We provide recommendations and research suggestions for the conservation of this species.

Invasive aquatic plants are considered the second cause of biodiversity loss in aquatic ecosystems. Pontederia crassipes Mart., formerly Eichhornia crassipes (Mart.) Solms (water hyacinth) is one of the most dangerous invasive species in the world. Since 2006, P. crassipes has invaded Lebanon’s Al Kabir River, causing ecological and socio-economic problems. To solve them, ecological and biological characteristics are important to understand the water hyacinth response to variations in environmental conditions. The aims of this study were (i) to analyze P. crassipes growth and (ii) physico-chemical parameters at two sites and (iii) to determine ecological relationships between P. crassipes and other plant species. The main results show the existence of different cohorts of water hyacinth at the two sites. Differences in growth between these cohorts are likely due to physico-chemical differences. In addition, P. crassipes coexist with other invasive and native plants. This ecological study can help ecologists and stakeholders map invasive plants in rivers and improve their control.

The seagrass Halophila stipulacea continues to spread rapidly through the Caribbean. Documenting native herbivore use of this invasive plant is important for understanding its impacts on marine communities and the mechanisms favoring its expansion. This study used observational and experimental data to determine if juvenile green turtles (Chelonia mydas) and long-spine urchins (Diadema antillarum) from the US Virgin Islands consumed H. stipulacea in the presence of native seagrass. Juvenile turtles associated significantly more with beds of native seagrass than mixed (native and invasive), and monospecific H. stipulacea, beds or sand bottoms. When individuals were followed, turtles foraged significantly more within mixed beds, but selectively fed on native species within them and were never observed feeding on monospecific H. stipulacea stands. When offered the native Thalassia testudinum and Syringodium filiforme, along with H. stipulacea, sea urchins significantly preferred S. filiforme over the other two choices. Measurements of fourteen nutritional and chemical parameters in these three seagrasses showed strong interspecific differences, with fewer and less predictable seasonal variations. Expressing these nutritional data by wet mass, rather than dry mass, also decreased the number of significant seasonal contrasts. Despite these differences, no parameters explained low herbivore preference for the invasive seagrass satisfactorily because nutrient values of H. stipulacea were often similar to those of the preferred natives. Our results conflict with recent studies pointing at low nutritional quality aiding against herbivory and suggest other mechanisms, such as herbivore learning and recognition of a novel resource, could be more important than currently appreciated.

Experimental studies were conducted for metabolomic profiling during seed germination and seedling development in Salicornia brachaita under saline conditions. The results revealed accumulation of sucrose, mannose, glycerol, methionine, tryptophan, glycerol, protocathechoic acid, and mannonic acid in germinating seeds. Abundance of rhamnose, glucose, glutamine, fructose, ornithine, quininic acid, proline and ketoglutaric acid were recorded during emergence of radical (EoR) and cotyledonary stage (CS) at 50% strength of seawater (SW) salinity. Higher levels of myo-inositol, ethanolamine, isoleucine and talose at 48 hours (hrs) of imbibition, EoR and CS stages; while glycine, tyrosine and turanose were so at CS stage only. Under 200 mM NaCl, richness of stearic acid, quercetin, leucine, erythritol and psicose were noted at 48 hrs of imbibition followed by EoR stage. Fructose, ornithine, mannitol, asparagine, mallic acid, glucose and citric acid were abundant at EoR whereas aminobutanoic acid, hexanedioic acid and tyramine were so at CS stage. Among detected metabolites maximum number of metabolites showed hits with amioacyl-tRNA biosynthesis pathway and the amino acid biosynthesis pathway had maximum impact during seedling development. Role of metabolic pathways (including amino acid metabolism) and differential expression of genes related to these pathways are suggested in meeting the energy needs for varied biological activities during seed germination and subsequent seedling development in S. brachiata.

Seagrasses are recognized for their fundamental and ecological functions in coastal environments. Movement ecology and dispersal mechanism of organisms are hypothesized to have a profound significance for the dynamics and resilience of populations and ecosystems. We tested this hypothesis by comparing the genetic diversity and fine-scaled structure of co-occurring seagrass populations of Thalassia hemprichii and Cymodocea serrulata, which differ in their survival strategy and movement ecology. Two hundred eighty-four and two hundred sixty-three individuals of T. hemprichii and C. serrulata from 6 seagrass meadows along Leyte, Philippines were genotyped using 15 and 9 microsatellite markers, respectively. Thalassia hemprichii was observed to have higher genotypic diversity, while clonal elongation was more pronounced for C. serrulata. Repeated seedling recruitment followed by rhizome elongation was observed as an important strategy of resilience and indicated the complementary importance of both sexual and asexual reproduction of these species. Moreover, fine-scale spatial structure analysis revealed that repeated seed recruitment and pollen flow occurred locally, yielding higher kinship values at very close distances of < 5 m, indicating its importance for the maintenance of genetic diversity. An individual based STRUCTURE analysis showed three putative gene pools for both species. Overall, our findings have important implications for understanding the processes and dynamics of populations before conservation efforts. Depending on the strategy of the species, efforts should focus on preserving natural expansion of existing beds and enabling local seed recruitment for successful conservation.

Many amphibious clonal plants in aquatic-terrestrial ecotones commonly expand from terrestrial to aquatic habitats. Nutrient availability and light intensity are both key factors affecting plant growth in aquatic habitats, but little is known about the role of nutrient availability and light intensity in aquatic habitats during the expansion of amphibious clonal plants from terrestrial to aquatic habitats, when clonal integration is maintained. We conducted a greenhouse experiment to simulate expansion from terrestrial to aquatic habitats of the amphibious clonal plant Hydrocotyle vulgaris. We grew basal portions of clonal fragments in soil and connected the apical portions of the same fragments to water which subjected to three levels of nutrient availability under a low or a high light condition. High nutrient level and light condition increased the growth of the apical portions of H. vulgaris and thus increased the performance of the whole clones. Meanwhile, root-shoot mass ratio of the apical portions and the basal portions were higher at the high light condition and the low nutrient level. Results suggest that the relatively high levels of nutrients and light condition in aquatic habitats can improve the expansion of apical portions from terrestrial to aquatic habitats. Our results also suggest that maintaining clonal integration may benefit the expansion of H. vulgaris via the trade-off of biomass allocation which can optimize the utilization of resources. These results may provide theoretical basis for community dynamics prediction and vegetation restoration in the ecotones such as wetlands.

Hurricane Sandy struck the New York metropolitan region on October 29, 2012. The storm severely impacted the physical state of Barnegat Bay, New Jersey with its heavy storm surge, affecting many forms of benthic life and ripping up extensive beds of Zostera marina. Pre-Sandy studies of the genetic status of Z. marina in Barnegat Bay indicated low levels of heterozygosity and high levels of inbreeding. This present study examines the long-term effects of Hurricane Sandy on the eelgrass meadows of New Jersey. Heterozygosity analysis (mean Ho= 0.482 ± 0.013 and mean He= 0.498± 0.009) of the five Barnegat populations studied suggest an improvement in diversity from pre-Sandy values of 2008. Mean inbreeding levels (overall Fis = 0.077 ± 0.034) also indicated reduced inbreeding, and the fixation index (overall mean pairwise Fst = 0.064 ±0.006) suggested increased connectivity between populations with low levels of differentiation. Although we found no indication of bottlenecks in the last 2–3 years, by employing m-ratio calculations, there was strong evidence for long-term, historical bottlenecks in all populations, potentially due to the mass wasting disease epidemic in the 1930s. Unexpectantly, the post-Sandy genetic health and diversity of Z. marina in Barnegat Bay appears to have improved since it was last surveyed in 2008, supporting the “Storm Stimulus” hypothesis.

Climate change is altering the world’s marine biota, in particular, their geographic distribution. Sargassum species are foundation species that play critical ecological roles in tropical benthic communities, providing food, habitat heterogeneity and shelter for a wide range of marine organisms. To understand how future changes in abiotic variables could affect the distribution of Sargassum species along the Western Atlantic Ocean, we performed Ecological Niche Models (ENM) for 12 benthic Sargassum species. We projected present and future habitat suitability distributions under the RCP 4.5 and RCP 8.5 IPCC scenarios. We fit ENM and created ensembles from different algorithms. Our results predict changes in species latitudinal range (niche suitability) in the order of 0.5˚ to 8.1˚ northward, and 0˚ to 5.5˚ southward. Six species are likely to reduce their suitability area from 10% to 80%, while other six species are likely to expand their suitability area from 4% to 168%. Overall, changes in suitability area and latitudinal ranges will increase at larger latitudes for most species while suitability areas will decrease at lower latitudes for half of the species. This pattern is consistent with the expected tropicalization of temperate latitudes following global warming. Such changes can produce considerable losses in ecosystem services maintained by healthy Sargassum beds, particularly at lower latitudes. Our findings highlight the need to improve Sargassum conservation policies and management strategies to avoid the negative effects caused by losses in Sargassum forests.