Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 7

Liczba wyników na stronie
first rewind previous Strona / 1 next fast forward last
Wyniki wyszukiwania
Wyszukiwano:
w słowach kluczowych:  endangered species
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 1 next fast forward last
EN
The montane glades in the Polish Carpathians were created centuries ago and have lasted mainly as a result of mowing and grazing. The observed abandonment of traditional methods of tillage in the last century led to adverse changes in vegetation cover, including a decrease in floristic diversity and the disappearance of many plant species and associations. One of a rare mountain taxa in Poland is the alpine globeflower Trollius altissimus Crantz. The investigations were carried out between June and September 2014 in the Hala Długa glade (Gorce Mts.) at two 36 m2 plots: extensively grazed (P1) and unmanaged (P2). Light intensity, abundance and density of individuals and ramet clusters were significantly greater in the extensively grazed plot, whereas height of plant canopy, length of basal leaf petioles, width of leaf lamina, number and length of generative stems, number of flowers and follicles achieved higher values in the unmanaged plot. The structure of developmental stages and number of basal leaves did not differ remarkably between the studied sites. Also, the soil properties in both plots were very similar. The studies show that extensive sheep grazing has a positive influence on Trollius altissimus. In the studied locality such management contributes to the gradual spreading of this species. However, too intensive pasturage might eliminate this species as it has never been observed in any of the permanently grazed patches in the vicinity.
EN
Salix myrtilloides L. is an endangered species whose western limit of range runs through Poland. The main aim of the study was to increase the knowledge on the ecology and biology of S. myrtilloides populations in the Polesie Lubelskie region (Eastern Poland) in order to create an effective protection program. An 80% decrease in its population was found in this area. Our study was conducted to identify the mechanisms responsible for the process of withdrawal of this species from its natural stands by determining whether the processes of generative reproduction (pollen viability and germinability, seed germination ability and dynamics) in the populations occur properly and by characterizing within- and among-population genetic diversity of S. myrtilloides, using ISSR (Inter-Simple Sequence Repeat) primers. The results confirmed that S. myrtilloides pollen viability was high (84.17±8.67), and so were the seed germination ability (76% of the total number of sown seeds/24 h) and dynamics. The within-population genetic diversity was quite high for this species and the inter-population genetic variation was of medium value (ΦPT=0.148). The condition of two populations, their genetic diversity and sex ratio as well as the correctness of the investigated reproductive cycle stages altogether give prospects for their survival. It seems to be very important to start conservation involving the reintroduction and reconstruction of S. myrtilloides populations in the Polesie Lubelskie region. The proposed method for restoration of S. myrtilloides resources would be possible if ex situ cultivation and in vitro methods were used.
EN
Many species that are in danger of extinction require human support in the form of captive-breeding programs to help maintain their populations in the wild.When breeding in captivity, it is important to select breeding pairs that will create the most genetically diverse progeny. Based on the polymorphism of their microsatellite loci, breeding pairs of diploid land animals have been successfully selected. In this theoretical paper, we asked how to adapt this technique to the selection of spawner pairs for restocking populations of partially tetraploid fish species. To test our calculation techniques, we used actual data on the polymorphism of the loci of captured whitefish (Coregonus lavaretus). The data enabled calculations showing which spawner pairs would create the most genetically diverse cohort of offspring if they were bred. Themethod presented in the paper can be used for breeding fish in aquaculture conditions to help conserve species.
EN
Climate change is considered one of the greatest threats to biodiversity in future decades. Learning about the habitat preferences and geographical distributions of endangered species is critical for conservation management and planning in the context of climate change. This study investigated the effects of climate change on suitable habitat for Arborophila rufipectus Boulton, an endangered species that is endemic to southwest China. We used the known presence records for this species and a series of environmental variable layers to develop a predictive distribution model using maximum entropy modelling; this model was then used to assess the effects of future climate change on suitable habitat for this species. Our study indicated that climate change might have significant effects on suitable habitat for this species. By 2050, under a no-dispersal hypothesis, more than four-fifths of the habitat currently assessed as suitable would be lost, and the mean latitude of suitable habitat would shift northward by more than 100 kilometres. Based on this model, climate change would also aggravate habitat fragmentation. Under a full-dispersal hypothesis, all four climate trajectories developed by the Canadian Centre for Climate Modelling and Analysis (Ccma) and the Commonwealth Scientific and Industrial Research Organization (CSIRO) present similar trends: the area of suitable habitat is predicted to increase substantially, and habitat fragmentation would be mitigated under the two climate trajectories developed by the Goddard Institute for Space Studies (GISS). Finally, we offer some practical proposals for the future conservation of this endangered species.
EN
Primula farinosa L. of Primulaceae family is a protected, rare and critically endangered species of Polish flora. All lowland sites of this species do not longer exist at present. The population number of the only one mountainous site discovered in 1959 in Beskid Sądecki (South Poland) is violently decreasing. The reasons for decrease in the population can be complex and associated with changes in both habitat changes and low effectiveness of propagation. In the course of the study, the population number was estimated and selected aspects of the biology of flowering of P. farinosa were assessed, phytosociological and habitat characteristics of the environment were prepared. The population amounted to 158 flowering specimens in 2011. Improper age structure of the population, characterized by a small share of juvenile plants indicates a possible regression of the population. The share of expansive species increased in the floristic composition of phytocoenosis as compared to historical sources. The assessed elements of generative propagation do not provide any grounds to suppose that the decrease of the population number is caused by disturbances in this field. High- and short-styled flowers are present in the population, a pollen is viable and new seeds are potentially able to germinate.
EN
At present Lychnothamnus barbatus (Meyen) Leonhardi belongs to the rarest species of charophytes in the world. In Europe it is classified as threatened with extinction. The problem of extinction of this species is intriguing, in particular in the context of its widespread occurrence in Europe and Asia till the last decade of the 20th century. Records of L. barbatus from Wielkopolska region (Western Poland) are know from 15 lakes. The most of them was stated in 19th and on beginning of 20th centuries. Now, this species is growing in 6 lakes, from among 2 sites are new. This study was undertaken to a) determine the abundance of L. barbatus and the co-occurring plant species at different sites in lakes, b) determine the most important ecological parameters controlling the structure communities with L. barbatus co-occurring and quantitative responses of this species. In 7 lakes (area 5.5-197 ha, depth max. 7.8-38 m, trophic state: meso-eutrophic) in western Poland the species composition and coverage of vegetation were studied at the 23 plots with L. barbatus occurrence in relation to the measured variables. Seventeen environmental parameters were measured including: depth of water, pH, conductivity, SO[4^2-], NH[4^+], NO[^3-], PO[4^3-], Na[^+], K[^+], Ca[^2+], Mg[^2+], chlorophyll a, Secchi disc visibility, colour, O[2] dissolved, saturation, total Fe during the period July-September. The DCA and CCA analyses were used to assess the relation between vegetation parameters and environmental variables. L. barbatus preferred the water rich in Ca[^+], Mg[^2+] and SO[4^2-] and with high concentrations of nutrients, especially NH[4^+] and PO[4^3-], and moderate values of electrolytic conductivity. In the studied lakes, L. barbatus occupied the separate niche. This species formed the communities in very shallow marginal zones of lakes (0.4-1.5 m) with other macrophytes like: Chara vulgaris, C. tomentosa, Potamogeton nitens, and monospecific stands on margins of steep lake slopes (4-6 m) with Chara globularis fo. hedwigii and Nitella mucronata. The process of extinction of this species seems to be related with increasing turbidity related in turn to algal blooming in lakes and with the spatial competition of vascular macrophytes, especially Ceratophyllum demersum.
EN
Six subterranean stream habitats in the central USA that contain rare and endangered cave animals were investigated. Water, sediment, and animal tissue were sampled to determine the degree of pollution inputs, and natural abundance stable carbon and nitrogen isotope analyses were employed to determine trophic structure and hypothetical influence of nutrient pollutants. Environmental quality sampling revealed contamination of water, sediments, and animal tissue by nutrients, toxic metals, and coliform bacteria, originating probably from septic systems and land application of animal feedlot wastes. Stable isotope analyses did not detect nutrient pollutants in the food webs of these habitats, but these analyses did elucidate trophic structure. Three trophic levels are evident in these subterranean streams: a detrital food base of clastic sediment, bat guano, and surface inputs; a second trophic level of detritivores, primarily crustaceans and amphibians; and a top level of predators, primarily fishes. Monitoring and management of sediment quality and flux is recommended to protect subterranean stream habitats.
first rewind previous Strona / 1 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.